WO2008067841A1

WO2008067841A1 - Plants having improved fiber characteristics and method for making the same

Info

Publication number: WO2008067841A1
Application number: PCT/EP2006/011856
Authority: WO
Inventors: Magnus Hertzberg; Göran Sandberg; Jarmo Schrader; David SÖDERSTRÖM; Linus MÖLLER
Original assignee: SweTree Technologies AB
Current assignee: SweTree Technologies AB
Priority date: 2006-12-08
Filing date: 2006-12-08
Publication date: 2008-06-12
Anticipated expiration: 2009-06-08
Also published as: WO2008069745A1; CL2007003531A1

Abstract

The present invention pertains to a novel and extensive analytical platform for selecting genes with a possible commercial phenotype from a large group of candidate genes identified using tools in bioinformatics, data from EST sequencing and DNA array. The analytical platform is concentrated on analyses of fiber length and/or width and growth behavior based on a combination of multiple criteria. An object of the present invention relates to a method of producing a transgenic plant having an increased fibre length and/or width compared to its wild type. The method comprises altering in the plant the level of a gene product of at least one gene specifically expressed during different phases of wood formation phases. Further aspects of the invention provide a plant cell or plant progeny of a transgenic plant comprising a recombinant polynucleotide according to the invention. Other aspects pertain to wood produced by a transgenic plant of the invention as well as a DNA construct comprising a nucleotide sequence of the invention and a plant cell or plant progeny comprising the DNA construct.

Description

PLANTS HAVING IMPROVED FIBER CHARACTERISTICS AND METHOD FOR MAKING THE SAME

Technical field of the invention

The present invention relates generally to the field of molecular biology and relates to a method for improving plant fiber characteristics. More specifically, the invention relates to a method for phenotypically modifying plants and transgenic plants having altered expression of a gene specifically expressed during different phases of wood formation phases resulting in a modified fiber or fiber/growth phenotype. The invention also provides constructs useful in the method of the invention.

Background of the invention

At present, the primary objectives of forest-tree engineering and molecular breeding are to improve wood quality and yield. Currently, there is an increasing demand for wood products having special characteristics such as improved strength and reduced or increased mass. The further development of such differentiated products is merited by the fact that wood is being used for increasingly diverse and specific purposes such as a semi- manufacture for production of commodities and for specific construction purposes. Forestry plantations may also have advantages as a carbon sequestration crop in response to increasing atmospheric CO₂. Similarly, increased production of biomass from non-woody plants is desirable, for instance in order to meet the demand for raw material for energy production. Modification of specific processes during cell development in higher species is therefore of great commercial interest, not only when it comes to improving the properties of trees, but also other plants.

Plant growth by means of apical meπstems results in the development of sets of primary tissues and in lengthening of the stem and roots. In addition to this primary growth, tree species undergo secondary growth and produce the secondary tissue "wood" from the cambium. The secondary growth increases the girth of stems and roots.

Sterky et al. (Proc. Natl. Acad. So. USA, 1998 (95), 13330- 13335) have published the results of a large-scale gene discovery program in two poplar species, comprising 5,629 expressed sequence tags (ESTs) from the wood forming tissues of Populus tremula L. x tremuloides Michx. and Populus trichocarpa Tπchobel.' These ESTs represented a total of 3,719 unique transcripts for the two cDNA libraries and putative functions could be assigned to 2,245 of these transcripts. The authors state that the EST data presented will be valuable in identifying genes involved in the formation of secondary xylem and phloem in plants, but fail to give clear directions as to how the identification could be performed. The Sterky er al. paper also revealed the existence of a very large number of ESTs with unknown or uncertain functions.

In the prior art (Sterky et al. ) libraries were constructed from stem tissue isolated from actively growing trees. A cambial region library was prepared from a mix of tissues, including the developing xylem, the meπstematic cambial zone, and developing and mature phloem of P. Tremula X tremuloides Michx. These cambial tissues were obtained by peeling the bark and scraping both exposed surfaces with a scalpel. A developmg-xylem library was prepared from Populus trichocarpa Tπcobel. These tissues were obtained by peeling the bark and scraping the exposed xylem side. Using such methods it is only possible to build three different libraries representing the whole cambial region, the developmg-xylem and the phloem region (made from scraping the exposed bark). The prior art compared the expression of genes in the cambial-region with the genes expressed in the developing xylem tissue. The experiment only allowed a crude comparison due to the limits imposed by the tissue preparation protocol. The tissue used for the developing xylem library would contain tissues from expanding xylem cells through to late xylem development.

One problem remaining is how to identify the potentially most important genes and to relate these to specific developmental stages and final properties of the cell. Another problem is how to identify hitherto unknown genes, related to specific cell types and/or functions in the plant. Finally, a particular problem is how to find the specific genes involved in cell division, cell expansion, cell wall synthesis, apoptosis and programmed cell death and other important processes involved in determining tree growth and wood properties.

Hertzberg et al. 2001 (Proc. Natl. Acad. Sci. USA, 2001 (98), 14372 - 14737), and Schrader et al. 2005 (Plant Cell, (16), 2278 - 2292) have used transcript profiling to reveal a transcriptional hierarchy for thousands of genes during xylem development as well as providing expression data that can facilitate further elucidation of many genes with unknown function (White et al. 1999 (Science 1999 (286) 2187 - 2184); Aharoni et al. 2000 (Plant Cell 2000 (12) 647 - 662). This is however technically demanding in woody plants such as trees. Hertzberg et al. and Schrader et al. have studied the developing secondary xylem of poplar, which is highly organized with easily recognized and distinct boundaries between the different developmental stages. Wood formation is initiated in the vascular cambium. Cambial derivatives develop into xylem cells through the processes of division, expansion, secondary wall formation, lignification and, finally, programmed cell death. The large physical size of the vascular meristem in trees offers a unique possibility to obtain samples from defined developmental stages by tangential cryo sectioning (Uggla et al. 1996 Proc. Natl. Acad. Sa. USA, 1996 (93), 9282 - 9286). To determine the steady state mRNA levels at specific stages during the ontogeny of wood formation in Populus tremula x tremuloides (hybrid aspen) 30 μm thick sections through the wood development region were sampled and subsequently analyzed using several spotted cDNA-microarray (Schena et al. 1995 Science 1995 (270) 467 - 470) consisting of up to 20.000 unique ESTs from hybrid aspen.

Although it is obvious that results from EST programs, genome sequencing and expression studies using DNA array technologies can verify where and when a gene is expressed it is rarely possible to clarify the biological and/or technical function of a gene only from these types of analytical tools. In order to analyze and verify the gene function a functional characterization must be performed, e.g. by gene inactivation and/or gene over- expression. However, in order to be able to identify genes with interesting and most often unexpected commercial features, there is a need for novel analytical platforms evaluating candidate genes based on multiple criteria.

Summary of the invention The present invention pertains to a novel and extensive analytical platform for selecting genes with a possible commercial phenotype from a large group of candidate genes identified using tools in bioinformatics, data from EST sequencing and DNA array. The analytical platform is concentrated on analyses of fiber length and/or width and growth behavior based on a combination of multiple criteria. The invention provides a method for producing a transgenic plant by changing the expression of one or more genes selected from a group of genes which fulfil said criteria.

Thus, an object of the present invention relates to a method of producing a transgenic plant having an increased fibre length and/or width compared to its wild type, comprising altering in the plant the level of a gene product of at least one gene specifically expressed during different phases of wood formation phases.

In a particular embodiment of the invention, the at least one gene is selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes: a) an increase of 10% or more in average fibre length (AFL) or a decrease of 15% or more in average fibre length (AFL), and/or b) an increase of 10% or more in average fibre width (AFW) or a decrease of 15% or more in average fibre width (AFW), and/or c) an increase of 10% or more in maximum fibre length (maxFL) or a decrease of 15% or more in minimum fibre length (minFL), and/or d) an increase of 10% or more in maximum fibre width (maxFW) or a decrease of

15% or more in minimum fibre width (minFW), when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photopeπod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions.

In a further embodiment of the invention, the at least one gene is also selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes: a) a difference of 5% or more in average final height (AFH) and maximum final height (MFH) and average maximum height growth rate (AMHGR) and maximum maximum height growth rate (MMHGR); and/or b) a difference of 5% or more in average final diameter (AFD)and maximum final diameter (MFD) and average diameter growth rate (ADGR) and maximum diameter coefficient (MDC); and/or c) a difference of 18% or more in average final height (AFH) and/or average final diameter (AFD) and/or average maximum height growth rate (AMHGR) and/or average diameter growth rate (ADGR); and/or d) a difference of 18% or more in maximum final height (MFH) and/or maximum final diameter (MFD) and/or maximum maximum height growth rate (MMHGR) and/or maximum diameter coefficient (MDC);

when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photopeπod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions; wherein the maximum height growth rate is defined by calculating the slope of a linear function fitted over four consecutive height data points, a height growth rate value is calculated for data point 1-4, data point 2-5 etc. in a step-wise manner and the maximum height growth rate value is finally selected from the growth rate values for each plant.

A number of genes analyzed using the novel analytical platform show interesting and most often unexpected commercial features. Thus, another aspect of the invention relates to a transgenic plant comprising a recombinant polynucleotide (DNA construct) comprising a nucleotide sequence capable of altering in the plant the level of a gene product of at least one gene specifically expressed during wood formation phases, wherein said gene is selected for conforming to the criteria that RNAi down-regulation of the gene in a group of 3-8 transgenic plants causes: a) an increase of 10% or more in average fibre length (AFL) or a decrease of 15% or more in average fibre length (AFL), and/or b) an increase of 10% or more in average fibre width (AFW) or a decrease of 15% or more in average fibre width (AFW), and/or c) an increase of 10% or more in maximum fibre length (maxFL) or a decrease of

15% or more in minimum fibre length (minFL), and/or d) an increase of 10% or more in maximum fibre width (maxFW) or a decrease of

15% or more in minimum fibre width (minFW), when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photopeπod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2 g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions.

In a further embodiment of the invention, the gene is further selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes: a) a difference of 5% or more in average final height (AFH) and maximum final height (MFH) and average maximum height growth rate (AMHGR) and maximum maximum height growth rate (MMHGR); and/or b) a difference of 5% or more in average final diameter (AFD)and maximum final diameter (MFD) and average diameter growth rate (ADGR) and maximum diameter coefficient (MDC); and/or c) a difference of 18% or more in average final height (AFH) and/or average final diameter (AFD) and/or average maximum height growth rate (AMHGR) and/or average diameter growth rate (ADGR); and/or d) a difference of 18% or more in maximum final height (MFH) and/or maximum final diameter (MFD) and/or maximum maximum height growth rate (MMHGR) and/or maximum diameter coefficient (MDC);

Another aspect of the invention provides a plant cell or plant progeny of a transgenic plant according to the invention and comprising a recombinant polynucleotide.

A further aspect of the invention provides wood produced by a transgenic plant having the characteristics described above.

Still another aspect of the invention provides a DNA construct comprising at least one sequence as described as described above.

Finally, one aspect of the invention provides a plant cell or plant progeny comprising the DNA construct according to the invention.

Brief description of the figures

Fig. 1 shows the different phases of wood formation, wherein (A) is a cross section of a hybrid aspen stem stained with Toluidme blue. Black bars indicate the location of the sampled tissues. The phloem sample was included in order to give a low-resolution picture of the gene expression in the other tissue derived from the cambium. (B) is a schematic representation of different cell-types and stages during vascular development. Bars depict timing and extent of the different developmental stages and the appearance of the major cell wall components. (C) shows a hierarchical cluster analysis of 1791 selected genes with differential expression in the sampled tissues. The colour scale at the bottom depicts fold change between samples. (D) (I-X) shows groups of genes with different differential expression patterns, expression ratios in Iog2 scale. The samples are indicated at the bottom of the figure.

Fig. 2 shows the expression patterns for the selected genes, from the xylem differentiation data. 9 principal examples of genes selected from the Hertzberg et al data set for functional analysis in Hybrid aspen. The same samples and figure as in Fig. 1 D, The graphs show the expression pattern of those genes over the xylem differentiation zone. Expression ratios are on log scale.

Fig. 3 shows the expression patterns for the selected genes from the meristem experiment data. 6 principal examples of genes selected from the Schrader et al data set for functional analysis in Hybrid aspen. The same samples and figure as in figure xl D, The graphs shows the expression pattern of those genes over the cambial zone. Expression data is from the B series from the Schrader et al 2004 paper. Expression values are on log scale, for an explanation of the normalization and data preparation See Schrader et al 2004; and

Fig. 4 shows an example of a height growth curve with 4 different data point linear regression lines shown

The present invention will now be described in more detail in the following.

Detailed description of the invention

Definitions

Prior to discussing the present invention in further details, the following terms and conventions will first be defined: The term "transgenic plant" refers to a plant that contains genetic material, not found in a wild type plant of the same species, variety or cultivar. The genetic material may include a transgene, an insertional mutagenesis event (such as by transposon or T-DNA insertional mutagenesis), an activation tagging sequence, a mutated sequence, a homologous recombination event or a sequence modified by chimeraplasty. Typically, the foreign genetic material has been introduced into the plant by human manipulation. The term also refers to plants in which genetic material has been inserted to function as a selection marker. Examples of such selectable markers include kanamycin, hygromycin, phosphoinotπcin, chlorsulfron, methotrexate, gentamycin, spectιnomyαn,ιmιdazolιnones, d- aminoaαds and glyphosate. The term "fiber length" relates in the present context to the average fiber length in a wood sample or a stem sample of a plant.

The term "fiber width" relates in the present context to the average fiber width in a wood sample or a stem sample of a plant.

Thus, the expressions "increased fibre length" and "increased fibre width" relates in the present context to an increase in the fibre length and an increase in fibre width, respectively, of a transgenic plant relative to the wild-type plant from which the transgenic plant is derived, when grown under the same growth conditions. As described below, a transgenic plant is characterized by having an increased fibre length if the plant meets at least one of the "fibre length difference selection criteria" as defined in the description and examples below. Similarly, a transgenic plant is characterized by having an increased fibre width if the plant meets at least one of the "fibre width difference selection criteria" as defined in the description and examples below

In the present context the term "growth" includes primary growth, including a lengthening of the stem and roots, as well as secondary growth of a plant, including production of secondary tissue, "wood", from the cambium and an increase in the girth of stems and roots. Thus, the expression "increased growth" relates in the present context to an increase growth of a transgenic plant relative to the wild-type plant from which the transgenic plant is derived, when grown under the same growth conditions. As described below, a transgenic plant is characterized to have an increased growth if the plant meets at least one of the "growth difference selection criteria" as defined in the below Examples.

The term "phenotype" refers in the present context to an individual plant's total physical appearance, such as growth. Examples of different fibre phenotypes used in the present context are listed in the below table 1 2 and comprise e.g. a phenotype named "AFL" which refers to an average fibre length of the wild type population and each construction group population, or "AFW" average fibre width of the wild type population and each construction group population. Similarly, examples of different growth phenotypes used in the present context are listed in the below table 1.3 and comprise e.g. a phenotype named "AFH" which refers to an average final height of the wild type population and each construction group population, or "AFD" average final diameter of the wild type population and each construction group population.

In the context of the present invention the term "phases of wood formation" refers to stages of wood formation, such as cell division and cell expansion, as defined in: Wilson, B. F., Wodzicki, T.J. and Zhaner,R. (1966) Differentiation of cambial deπvates: Proposed terminology. Forest Science 12, pp438-440.

When discussing a gene that is specifically expressed during different phases of wood formation, the term "specifically expressed" is used as a designation of genes the expression of which is increased during wood formation phases. It will be understood that the expression of said genes during phases of wood formation may be increased by 10% or more, such as by 15% or more, 20% or more, 25% or more, 30% or more, 40% or more, 50% or more, 75% or more, 100% or more, 200% or more, 300% or more, 400% or more, 500% or more, 700% or more or 1000% or more.

The term "gene" broadly refers to any segment of DNA associated with a biological function. Genes include coding sequences and/or regulatory sequences required for their expression. Genes also include non-expressed DNA nucleic acid segments that, e.g., form recognition sequences for other proteins (e.g., promoter, enhancer, or other regulatory regions). Genes can be obtained from a variety of sources, including cloning from a source of interest or synthesizing from known or predicted sequence information, and may include sequences designed to have desired parameters.

The term "RNA interference" or "RNAi" refers generally to a process in which a double- stranded RNA molecule or a short hairpin RNA changes the expression of a nucleic acid sequence with which they share substantial or total homology.

The term "RNAi down-regulation" refers to the reduction in the expression of a nucleic acid sequence mediated by one or more RNAi species. The term "RNAi species" refers to a distinct RNA sequence that elicits RNAi.

The term "photoperiod" refers to the daily cycle of light and darkness.

The terms "nucleic acid construct", "DNA construct" and "vector" refer to a genetic sequence used to transform plants or other organisms. The nucleic acid construct or DNA construct may be able to direct, in a transformed plant the expression of a protein or a nucleic acid sequence, such as for example an antisense RNA. Typically, such a nucleic acid construct or DNA construct comprises at least a coding region for a desired gene product or a desired nucleic acid product operably linked to 5' and 3' transcriptional regulatory elements. In some embodiments, such nucleic acid constructs or DNA constructs are chimeric, i.e. consisting of a mixture of sequences from different sources. However, non- chimeric nucleic acid constructs or DNA constructs may also be used in the present invention.

The term "recombinant" when used with reference, e.g., to a cell, nucleotide, vector, protein, or polypeptide typically indicates that the cell, nucleotide, or vector has been modified by the introduction of a heterologous (or foreign) nucleic acid or the alteration of a native nucleic acid, or that the protein or polypeptide has been modified by the introduction of a heterologous amino acid, or that the cell is derived from a cell so modified. Recombinant cells express nucleic acid sequences (e.g., genes) that are not found in the native (non-recombinant) form of the cell or express native nucleic acid sequences (e.g. genes) that would be abnormally expressed under-expressed, or not expressed at all. The term "recombinant" when used with reference to a cell indicates that the cell replicates a heterologous nucleic acid, or expresses a peptide or protein encoded by a heterologous nucleic acid. Recombinant cells can contain genes that are not found within the native (non-recombinant) form of the cell. Recombinant cells can also contain genes found in the native form of the cell wherein the genes are modified and re- introduced into the cell by artificial means. The term also encompasses cells that contain a nucleic acid endogenous to the cell that has been modified without removing the nucleic acid from the cell; such modifications include those obtained by gene replacement, site- specific mutation, and related techniques.

The term "nucleic acid sequence" refers to a polymer of deoxyribonucleotides or ribonucleotides in either single- or double-stranded form. Unless specifically limited, the term encompasses nucleic acid sequences containing known analogues of natural nucleotides which have similar binding properties as the reference nucleic acid and are metabolized in a manner similar to naturally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence also implicitly encompasses conservatively modified variants thereof (e.g., degenerate codon substitutions) and complementary sequences and as well as the sequence explicitly indicated.

A "polynucleotide" is a nucleic acid sequence comprising a plurality of polymerized nucleotide residues, e. g., at least about 15 consecutive polymerized nucleotide residues, optionally at least about 30 consecutive nucleotides, at least about 50 consecutive nucleotides. In many instances, a polynucleotide comprises a nucleotide sequence encoding a polypeptide (or protein) or a domain or fragment thereof. Additionally, the polynucleotide may comprise a promoter, an intron, an enhancer region, a polyadenylation site, a translation initiation site, 5'or 3' untranslated regions, a reporter gene, a selectable marker, or the like. The polynucleotide can be single stranded or double stranded DNA or RNA. The polynucleotide optionally comprises modified bases or a modified backbone. The polynucleotide can be e. g. genomic DNA or RNA, a transcript (such as an mRNA), a cDNA, a PCR product, a cloned DNA, a synthetic DNA or RNA, or the like. The polynucleotide can comprise a sequence in either sense or antisense orientation.

The term "polypeptide" is used broadly to define linear chains of amino acid residues, including occurring in nature and synthetic analogues thereof.

In the context of the present invention "complementary" refers to the capacity for precise pairing between two nucleotides sequences with one another. For example, if a nucleotide at a certain position of an oligonucleotide is capable of hydrogen bonding with a nucleotide at the corresponding position of a DNA or RNA molecule, then the oligonucleotide and the DNA or RNA are considered to be complementary to each other at that position. The DNA or RNA strand are considered complementary to each other when a sufficient number of nucleotides in the oligonucleotide can form hydrogen bonds with corresponding nucleotides in the target DNA or RNA to enable the formation of a stable complex.

In the present context the expressions "complementary sequence" or "complement" therefore also refer to nucleotide sequences which will anneal to a nucleic acid molecule of the invention under stringent conditions. The term "stringent conditions" refers to general conditions of high, weak or low stringency.

The term "stringency" is well known in the art and is used in reference to the conditions (temperature, ionic strength and the presence of other compounds such as organic solvents) under which nucleic acid hybridisations are conducted. With "high stringency" conditions, nucleic acid base pairing will occur only between nucleic acid fragments that have a high frequency of complementary base sequences, as compared to conditions of "weak" or "low" stringency. Suitable conditions for testing hybridization involve pre- soaking in 5xSSC and pre-hybπdizing for 1 hour at ~40°C in a solution of 20% formamide, 5xDenhardt's solution, 5OmM sodium phosphate, pH 6.8, and 50mg of denatured sonicated calf thymus DNA, followed by hybridization in the same solution supplemented with 10OmM ATP for 18 hours at ~40°C, followed by three times washing of the filter in 2xSSC, 0.2% SDS at 40⁰C for 30 minutes (low stringency), preferred at 50⁰C (medium stringency), more preferably at 65°C (high stringency), even more preferably at ~75°C (very high stringency). More details about the hybridization method can be found in Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd Ed., Cold Spring Harbor, 1989.

The terms "hybridization" and "hybridize" are used broadly to designate the association between complementary or partly complementary nucleic acid sequences, such as in a reversal of the process of denaturation by which they were separated. Hybridization occurs by hydrogen bonding, which may be Watson-Crick, Hoogsteen, reversed Hoogsteen hydrogen bonding, etc., between complementary nucleoside or nucleotide bases. The four nucleobases commonly found in DNA are G, A, T and C of which G pairs with C, and A pairs with T. In RNA T is replaced with uracil (U), which then pairs with A. The chemical groups in the nucleobases that participate in standard duplex formation constitute the Watson- Crick face. Hoogsteen showed a couple of years later that the purine nucleobases (G and A) in addition to their Watson-Crick face have a Hoogsteen face that can be recognised from the outside of a duplex, and used to bind pyπmidine oligonucleotides via hydrogen bonding, thereby forming a triple helix structure.

A "subsequence" or a "fragment" is any portion of an entire sequence. Thus, a fragment or subsequence refers to a sequence of amino acids or nucleic acids that comprises a part of a longer sequence of ammo acids (e.g. polypeptide) or nucleic acids (e.g. polynucleotide), respectively.

In the present context, the homology between two amino acid sequences or between two nucleotide sequences is described by the parameter "sequence identity". The term "sequence identity" indicates a quantitative measure of the degree of homology between two amino acid sequences or between two nucleic acid sequences of equal length. If the two sequences to be compared are not of equal length, they must be aligned to give the best possible fit, allowing the insertion of gaps or, alternatively, truncation at the ends of the 5 polypeptide sequences or nucleotide sequences. The sequence identity can be calculated as

^Nnl , wherein N_dlf is the total number of non-identical residues in the two sequences when aligned and wherein N_ref is the number of residues in one of the sequences. Hence, the DNA sequence AGTCAGTC will have a sequence identity of 75% with the sequence AATCAATC (N_dlf=2 and N_ref=8). A gap is counted as non-identity of the specific resιdue(s), i.e. the DNA 10 sequence AGTGTC will have a sequence identity of 75% with the DNA sequence AGTCAGTC (N_dlf=2 and N_ref=8).

With respect to all embodiments of the invention relating to nucleotide sequences, the percentage of sequence identity between one or more sequences may also be based on alignments using the clustalW software (http:/www ebi.ac.uk/clustalW/index.html) with default

15 settings. For nucleotide sequence alignments these settings are: Alιgnment=3Dfull, Gap Open 10.00, Gap Ext 0 20, Gap separation Dist. 4, DNA weight matrix: identity (IUB). Alternatively, the sequences may be analysed using the program DNASIS Max and the comparison of the sequences may be done at http://www.paraliqn.org/. This service is based on the two comparison algorithms called Smith-Waterman (SW) and ParAhgn. The first algorithm was

20 published by Smith and Waterman (1981) and is a well established method that finds the optimal local alignment of two sequences The other algorithm, ParAhgn, is a heuristic method for sequence alignment; details on the method is published in Rognes (2001). Default settings for score matrix and Gap penalties as well as E-values were used.

The phrase "substantially identical" or "substantial identity" in the context of two nucleic 25 acids or polypeptides, refers to two or more sequences or sub-sequences that have at least about 60%, 70%, 75%, preferably 80% or 85%, more preferably 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.5%, or greater nucleotide or amino acid residue percent identity, respectively, when compared and aligned for maximum correspondence, as measured using one of the following sequence comparison algorithms or by visual 30 inspection. In certain aspects, the substantial identity exists over a region of amino acid sequences of at least about 50 residues in length, such as, at least about 100, 110, 120, 125, 130, 135, 140, 145, 150, 155, 160, or 165 amino acid residues. In certain aspects, substantial identity exists over a region of nucleic acid sequences of at least about 150 nucleic acid residues, such as at least about 200, 250, 300, 330, 360, 375, 400, 425, 450, 35 460, or 480 nucleic acid residues. In some aspects, the amino acid or nucleic acid sequences are substantially identical over the entire length of the polypeptide sequence or the corresponding coding region. The term "Conservative substitutions" refers to substitutions within the group of basic amino acids (arginine, lysine and histidine), acidic amino acids (glutamic acid and aspartic acid), polar amino acids (glutamine and asparagine), hydrophobic amino acids (leucine, isoleuαne, valine and methionine), aromatic ammo acids (phenylalanine, tryptophan and tyrosine), and small ammo acids (glycine, alanine, serine and threonine). Amino acid substitutions which do not generally alter the specific activity are known in the art and are described, for example, by H. Neurath and R. L. Hill, 1979, In, The Proteins, Academic Press, New York. The most commonly occurring exchanges are Ala/Ser, Val/Ile, Asp/Glu, Thr/Ser, Ala/Gly, Ala/Thr, Ser/Asn, Ala/Val, Ser/Gly, Tyr/Phe, Ala/Pro, Lys/Arg, Asp/Asn, Leu/Ile, Leu/Val, Ala/Glu, and Asp/Gly as well as these in reverse.

The term "conservatively substituted variant" as used herein refers to a variant of a nucleotide sequence comprising one or more conservative substitutions.

Generally and in the present context, the term "silent substitution" refers to a base substitution which does not affect the sense of a codon and thus has no effect on polypeptide structure. As the skilled person will know silent substitutions are possible because of the degeneracy of the genetic code.

The term "conserved domain" refers to a sequence of amino acids in a polypeptide or a sequence of nucleotides in DNA or RNA that is similar across multiple species. A known set of conserved sequences is represented by a consensus sequence. Amino acid motifs are often composed of conserved sequences. Additionally, the term "conserved sequence" refers to a base sequence in a nucleic acid sequence molecule or an amino acid sequence in a protein that has remained essentially unchanged throughout evolution. A "consensus sequence" is defined in terms of an idealized sequence that represents the base most often present at each position in a nucleic acid sequence or the amino acid most often present at each position in a protein. A "consensus sequence" is identified by aligning all known examples of a nucleic acid sequence or a protein so as to maximise their sequence identity. For a sequence to be accepted as a consensus sequence each particular base or amino acid must be reasonably predominant at its position and most of the sequences must be related to the consensus by only few substitutions, such as 1 or 2.

The term "promoter," as used herein, refers to a region of sequence determinants located upstream from the start of transcription of a gene and which are involved in recognition and binding of RNA polymerase and other proteins to initiate and modulate transcription. Promoters useful in plants need not be of plant origin. A "basal promoter" is the minimal sequence necessary for assembly of a transcription complex required for transcription initiation. Basal promoters frequently include a TATA box" element usually located between 15 and 35 nucleotides upstream from the site of initiation of transcription. Basal promoters also sometimes include a CCAAT box" element (typically a sequence CCAAT) and/or a GGGCG sequence, usually located between 40 and 200 nucleotides, preferably 60 to 120 nucleotides, upstream from the start site of transcription. Promoters referred to herein as "constitutive promoters" actively promote transcription under most, but not necessarily all, environmental conditions and states of development or cell differentiation. Examples of constitutive promoters include the cauliflower mosaic virus (CaMV) 35S transcript initiation region and the 1' or 2' promoter derived from TDNA of Agrobacterium tumefaciens, and other transcription initiation regions from various plant genes, such as the maize ubiquitin- 1 promoter, known to those of skill. Organ-specific promoters may be, for example, a promoter from storage sink tissues such as seeds, potato tubers, and fruits , or from metabolic sink tissues such as meristems , a seed specific promoter such as the glutelin, prolamin, globulin, or albumin promoter from rice , a Vicia faba promoter from the legumin B4 and the unknown seed protein gene from Vicia faba , a promoter from a seed oil body protein, the storage protein napA promoter from Brassica napus, or any other seed specific promoter known in the art, e.g., as described in WO 91/14772. Furthermore, the promoter may be a leaf specific promoter such as the rbcs promoter from rice or tomato, the chlorella virus adenine methyltransferase gene promoter , or the aldP gene promoter from rice, or a wound inducible promoter such as the potato pin2 promoter.

An "inducible promoter" in the context of the present invention refers to a promoter which is regulated under certain conditions, such as light, chemical concentration, protein concentration, conditions in an organism, cell, or organelle, etc. An example of an inducible promoter is the HSP promoter and the PARSKl, the promoter from the Arabidopsis gene encoding a serine-threonine kinase enzyme and which is induced by dehydration, abscissic acid and sodium chloride. In essence, expression under the control of an inducible promoter is "switched on" or increased in response to an applied stimulus. The nature of the stimulus varies between promoters and may include the above environmental factors. Whatever the level of expression is in the absence of the stimulus, expression from any inducible promoter is increased in the presence of the correct stimulus.

As used herein, the term "tissue specific" refers to a characteristic of a particular tissue that is not generally found in all tissues, or may be exclusive found in a tissue of interest. In the present application, "tissue specific" is used in reference to a gene regulatory element (promoter or promoter plus enhancer and/or silencer), the gene it encodes, or the polypeptide product of such a gene. In the context of a gene regulatory element or a "tissue specific promoter", the term means that the promoter (and also other regulatory elements such as enhancer and/or silencer elements) directs the transcription of a linked sequence in a cell of a particular lineage, tissue, or cell type, but is substantially inactive in cells or tissues not of that lineage, tissue, or cell type. A tissue specific promoter useful according to the invention is at least 5-fold, 10-fold, 25-fold, 50fold, 100-fold, 500-fold or even 1,000 times more active in terms of transcript production in the particular tissue than it is in cells of other tissues or in transformed or malignant cells of the same lineage. In the context of a gene or the polypeptide product of a gene, the term tissue specific means that the polypeptide product of the gene is detectable in cells of that particular tissue or cell type, but not substantially detectable in certain other cell types. Particularly relevant tissue specific promoters include promoter sequences specifically expressed or active in the xylem forming tissue in a plant. Examples of such promoters are the Lmpl, Lmx2, Lmx3, Lmx4 and Lmx5 promoters, described in WO2004097024.

A "terminator sequence" refers to a section of genetic sequence that marks the end of gene or operon on genomic DNA for transcription. Terminator sequences are recognized by protein factors that co-transcriptionally cleave the nascent RNA at a polyadenylation signal, halting further elongation of the transcript by RNA polymerase. A nucleic acid is "operably linked" when it is placed into a functional relationship with another nucleic acid sequence. For instance, a promoter or enhancer is operably linked to a coding sequence if it increases the transcription of the coding sequence. "Operably linked" means that the DNA sequences being linked are typically contiguous and, where necessary to join two protein coding regions, contiguous and in reading frame. However, since enhancers generally function when separated from the promoter by several kilobases and intronic sequences may be of variable lengths, some polynucleotide elements may be operably linked but not contiguous.

In the context of the present invention the terms "transformation" and "transforming" are used interchangeably and as synonyms to "transfecting" and "transfection", respectively, to refer to the process of introducing DNA into a cell. The DNA constructs, including at least a portion of the gene or promoter of interest, can be introduced into host cells, which as stated previously, can be individual cells, cells in culture, cells as part of a host organism, a fertilized oocyte orgametophyte or an embryonic cell. By the term "introduction" when used in reference to a host cell is meant to refer to standard procedures known in the art for introducing recombinant vector DNA into the target host cell. Such procedures include, but are not limited to, transfection, infection, transformation, natural uptake, electroporation, biolistics and Agrobacterium.

By "regenerable cell" is meant a plant cell from which a whole plant can be regenerated. It will be understood that the regenerable cell is a cell that has maintained its genetic potential, also known in the art as "totipotency". It will further be understood that the regenerable cells, when grown in culture, may need the appropriate stimuli to express the total genetic potential of the parent plant. Method of producing a transgenic plant

Candidate genes for use in changing and/or modifying the phenotype of a plant with regard to fibre characteristics such as fibre length and/or width may be identified using prior art procedures, e.g. as described in Hertzberg et al. (2001) and Schrader et al. (2004). Candidate genes involved in regulating fibre and growth characteristics may also for example be identified among transcription factors with special features identified using prior art knowledge. Such identification of candidate genes is known in the art as being important in order to maximize the positive output of a functional genomics program directed against properties/functions with relation to fibre characteristics. Accordingly, a first aspect of the present invention provides a method of producing a transgenic plant having an increased fibre length and/or increased fibre growth compared to its wild type, comprising altering, in the plant, the level of a gene product of at least one gene specifically expressed during wood formation phases.

While based on the targeting of such candidate genes, the present invention provides a method of producing a transgenic plant which includes the targeting of a gene that has been further selected by a novel approach to functional analyses.

According to one embodiment of this aspect, the at least one gene is selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes: a) an increase of 10% or more in average fibre length (AFL) or a decrease of 15% or more in average fibre length (AFL), and/or b) an increase of 10% or more in average fibre width (AFW) or a decrease of 15% or more in average fibre width (AFW), and/or c) an increase of 10% or more in maximum fibre length (maxFL) or a decrease of

15% or more in minimum fibre length (minFL), and/or d) an increase of 10% or more in maximum fibre width (maxFW) or a decrease of 15% or more in minimum fibre width (minFW), when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photoperiod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions. In one embodiment of the invention, the at least one gene is also selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes: a) a difference of 5% or more in average final height (AFH) and maximum final height (MFH) and average maximum height growth rate (AMHGR) and maximum maximum height growth rate (MMHGR); and/or b) a difference of 5% or more in average final diameter (AFD) and maximum final diameter (MFD) and average diameter growth rate (ADGR) and maximum diameter coefficient (MDC); and/or c) a difference of 18% or more in average final height (AFH) and/or average final diameter (AFD) and/or average maximum height growth rate (AMHGR) and/or average diameter growth rate (ADGR); and/or d) a difference of 18% or more in maximum final height (MFH) and/or maximum final diameter (MFD) and/or maximum maximum height growth rate (MMHGR) and/or maximum diameter coefficient (MDC); when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photopeπod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions; and maximum wherein the maximum height growth rate is defined by calculating the slope of a linear function fitted over four consecutive height data points, a height growth rate value is calculated for data point 1-4, data point 2-5 etc. in a step-wise manner and the maximum height growth rate value is finally selected from the growth rate values for each plant.

A fertilizer containing 84 gram of N per liter, 2 gram of Pl per liter, and 56 gram of K per liter is currently available under the trade name Weibulls Rika S NPK 7-1-5. The composition of this fertilizer is as follows (all in g/l): N tot = 84, NO₃ = 55, NH₄ = 29, P = 12, K = 56, Mg = 7,2, S = 7,2, B = 0,18, Cu = 0,02, Fe = 0,84, Mn = 0,42, Mo = 0,03, Zn = 0,13

An advantage of the present invention is that it provides an extremely sensitive analytical platform for evaluating candidate genes involvement in determining fibre characteristics. While gene evaluation methods have previously been based the evaluation of phenotypes according to a single criterion, such as fibre length or diameter, the present method allows a phenotype to be characterised on the basis of multiple criteria, including average fibre length, maximum fibre length, average fibre width and maximum fibre width. Use of this analytical platform allows the identification and selection of new target genes to be used in methods for generating plants having improved fibre characteristics. Using a more simple approach these target genes would not have been considered to be involved determination of fibre characteristics or they would only have been considered to play a marginal role in generating the improved phenotype.

In specific embodiments of the invention advantageous plant phenotypes are generated by modifying, relative to the corresponding wild-type plant, the expression level of candidate genes that have been evaluated and selected according to the above criteria. According to these aspects a method is provided which comprises altering in the plant the level of a gene product of at least one gene comprising a nucleotide sequence selected from the group consisting of: a) a nucleotide sequence from SEQ ID NO: 1-7; b) a nucleotide sequence being at least 60% identical to a nucleotide sequence from

SEQ ID NO 1-7 c) a subsequence or fragment of a nucleotide sequence of a) or b).

The sequences specified by sequence ID numbers 1-7 represent partial sequences of the candidate genes as cloned from hybrid aspen. As the skilled person will understand, additional sequence from these genes 5' as well as 3' to the sequence described in SEQ ID NOs: 1-7 is readily achievable using conventional cloning techniques, such as those described in Sambrook et al.

Nucleic acid constructs According to more particular embodiments of the invention, the method comprises the step of providing a nucleic acid construct, such as a recombinant DNA construct, comprising a nucleotide sequence selected from the group consisting of: d) a nucleotide sequence comprising a sequence selected from SEQ ID NO: 1-7; e) a complementary nucleotide sequence of a nucleotide sequence of d); f) a sub-sequence or fragment of a nucleotide sequence of d) or e); g) a nucleic acid sequence being at least 60% identical to any one of the sequences in d), e) and f); and h) a nucleotide sequence which hybridizes under stringent conditions to a nucleotide sequence of d), e) or f). In further embodiments of the invention the nucleic acid sequence in c) or g) is at least 65% identical to any one of the sequences in a), c), d), e) or f), such as at least 70% identical, at least 75% identical, at least 80% identical, at least 85% identical, at least 87% identical, at least 90% identical, at least 95% identical, at least 97% identical, at least 98% identical, at least 99% identical, or at least 99.5% identical to any one of the sequences in a), c), d), e) or f). A variety of methods exist in the art for producing the nucleic acid sequences and nucleic acid/DNA constructs of the invention. Procedures for identifying and isolating DNA clones are well known to those of skill in the art, and are described in, e. g. Sambrook et al., Molecular Cloning-A Laboratory Manual (2nd Ed.), Vol. 1-3, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, 1989. Alternatively, the nucleic acid sequences of the invention can be produced by a variety of in vitro amplification methods adapted to the present invention by appropriate selection of specific or degenerate primers. Examples of protocols sufficient to direct persons of skill through in vitro amplification methods, including the polymerase chain reaction (PCR) the ligase chain reaction (LCR), Qbeta- replicase amplification and other RNA polymerase mediated techniques (e. g., NASBA), e. g., for the production of the homologous nucleic acids of the invention are found in Sambrook, supra.

Alternatively, nucleic acid constructs of the invention can be assembled from fragments produced by solid-phase synthesis methods. Typically, fragments of up to approximately 100 bases are individually synthesized and then enzymatically or chemically hgated to produce a desired sequence, e. g., a polynucleotide encoding all or part of a transcription factor. For example, chemical synthesis using the phosphoramidite method is well known to the skilled person. According to such methods, oligonucleotides are synthesized, purified, annealed to their complementary strand, hgated and then optionally cloned into suitable vectors.

As mentioned, the above described sequences are from hybrid aspen. As the skilled person will understand, homologues of the described sequences may be isolated from other species, non-limiting examples of which include acacia, eucalyptus, hornbeam, beech, mahogany, walnut, oak, ash, hickory, birch, chestnut, alder, maple, sycamore, ginkgo, palm tree, sweet gum, cypress, Douglas fir, fir, sequoia, hemlock, cedar, juniper, larch, pine, redwood, spruce and yew, apple, plum, pear, banana, orange, kiwi, lemon, cherry, grapevine, fig, cotton, bamboo, switch grass, red canary grass and rubber plants. Useful homologues of the described sequences may also be isolated from hardwood plants from the Salicaceae family, e.g. from the salix and populus genus. Members of this geneus are known by their common names: willow, poplar and aspen.

In particular, the nucleotide sequence according to the invention comprises a sequence selected from those of SEQ ID NOs: 8-14, or a complementary nucleotide sequence thereof.

It will be apparent that the sub-sequences or fragment in c) or f) as described above comprises at least 15 nucleotides, such as at least 16 nucleotides, at least 17 nucleotides, at least 18 nucleotides, at least 19 nucleotides, at least 20 nucleotides, at least 21 nucleotides, at least 22 nucleotides, at least 23 nucleotides, at least 24 nucleotides, at least 25 nucleotides, e.g at least 30 nucleotides, at least 35 nucleotides, at least 40 nucleotides, at least 45 nucleotides, at least 50 nucleotides, at least 55 nucleotides, at least 60 nucleotides, at least 65 nucleotides, at least 70 nucleotides, at least 75 nucleotides, at least 80 nucleotides, at least 85 nucleotides, at least 90 nucleotides, at least 95 nucleotides, or such as at least 100 nucleotides. In certain embodiments, the sub-sequences or fragment in c) or f) as described above comprises at least about 150 nucleic acid residues, such as at least about 200, 250, 300, 330, 360, 375, 400, 425, 450, 460, 480, 500, 600, 700, 800 such as at least about 900 nucleotides or such as at least about 1 kb, 1.1 kb, 1.2 kb, 1.3 kb, 1.4 kb, 1.5 kb, 1.6 kb, 1.7 kb, 1.8 kb, 1.9 kb, 2 kb, 2.1 kb, 2.2 kb, 2.3 kb, 2.4 kb, 2.5 kb, 2.6 kb, 2.7 kb, 2.8 kb, 2.9 kb or such as at least about 3 kb.

In particular, the method according to the present invention may comprise a step of providing a nucleic acid construct, such as a recombinant DNA construct, comprising a nucleotide sequence which relative to the particular sequences described, comprises conservative variations altering only one, or a few amino acids in the encoded polypeptide may also be provided and used according to the present invention. Accordingly, it is within the scope of the invention to provide and use a recombinant DNA construct comprising a nucleotide sequence which encodes a polypeptide comprising a conservatively substituted variant of a polypeptide of a).

Sequence alterations that do not change the amino acid sequence encoded by the polynucleotide are termed "silent" substitutions. With the exception of the codons ATG and TGG, encoding methionine and tryptophan, respectively, any of the possible codons for the same amino acid can be substituted by a variety of techniques, e. g., site-directed mutagenesis, available in the art. Accordingly, the present invention may also provide a recombinant nucleic acid construct, wherein the nucleotide sequence comprises a silent substitution in a nucleotide sequence.

In certain further embodiments of the invention, the sub-sequences or fragments have at least 65% sequence identity to a conserved domain of a nucleotide sequence as described above under item a) or d), such as at least 70% identical, at least 75% identical, at least 80% identical, at least 85% identical, at least 87% identical, at least 90% identical, at least 95% identical, at least 97% identical, at least 98% identical, at least 99% identical, or at least 99.5% identical to a conserved domain of a nucleotide sequence as described above under item a) or d). Approaches to obtaining altering the level of a gene product

This invention is used by lowering or in some instances abolishing the expression of certain genes, non limiting examples how this can be done are presented here. The nucleic acid construct or recombinant DNA construct as described above may be used for the identification of plants having altered fibre characteristics as compared to the wild-type. Such plants may for instance be naturally occurring variants or plants that have been modified genetically to exhibit altered fibre properties. For such purposes the nucleic acid construct or recombinant DNA construct according to the invention may be used e.g. as a probe in conventional hybridization assays or as a primer for specific amplification of nucleic acid fragments.

In addition, the nucleic acid construct or recombinant DNA construct according to the invention may be used for the purpose of gene replacement in order to modify the respective plant fibre phenotype.

Suppression of endogenous gene expression can for instance be achieved using a πbozyme. Ribozymes are RNA molecules that possess highly specific endoπbonuclease activity. The production and use of ribozymes are disclosed in U. S. Patent No. 4,987,071 and U. S. Patent No. 5,543,508. While antisense techniques are discussed below, it should be mentioned that synthetic ribozyme sequences including antisense RNAs can be used to confer RNA cleaving activity on the antisense RNA, such that endogenous mRNA molecules that hybridize to the antisense RNA are cleaved, which in turn leads to an enhanced antisense inhibition of endogenous gene expression.

Vectors in which RNA encoded by a relevant gene homologue is over-expressed can also be used to obtain co-suppression of a corresponding endogenous gene, e. g., in the manner described in U. S. Patent No. 5,231,020 to Jorgensen. Such co-suppression (also termed sense suppression) does not require that the entire gene sequence be introduced into the plant cells, nor does it require that the introduced sequence be exactly identical to the endogenous sequence of interest. However, the suppressive efficiency will be enhanced as specificity of hybridization is increased, e. g., as the introduced sequence is lengthened, and/or as the sequence similarity between the introduced sequence and the endogenous transcription factor gene is increased.

Vectors expressing an untranslatable form of gene, e. g., sequences comprising one or more stop codons, or nonsense mutation, can also be used to suppress expression of an endogenous transcription factor, thereby reducing or eliminating it's activity and modifying one or more traits. Methods for producing such constructs are described in U. S. Patent No. 5,583,021. In particular, such constructs can be made by introducing a premature stop codon into the gene.

One way of performing targeted DNA insertion is by use of the retrovirus DNA integration machinery as described in WO2006/078431. This technology is based on the possibility of altering the integration site specificity of retroviruses and retrotransposons integrase by operatively coupling the integrase to a DNA-binding protein (tethering protein). Enginering of the integrase is preferably carried out on the nucleic acid level, via modification of the wild type coding sequence of the integrase by PCR. The integrase complex may thus be directed to a desired portion or be directed away from an undesired portion of genomic DNA thereby producing a desired integration site characteristic.

Another such technology is the "Targeting Induced Local Lesions in Genomes", which is a non-transgenic way to alter gene function in a targeted way. This approach involves mutating a plant with for example ethyl methanesulfonate (EMS) and later locating the individuals in which a particular desired gene has been modified. The technology is described for instance in Slade and Knauf, Transgenic Res. 2005 Apr; 14(2): 109-15 and Henikoff, Till and Comai, Plant Physiol. 2004 Jun; 135(2):630-6.

Another method for abolishing the expression of a gene is by insertion mutagenesis using the T-DNA of Agrobacterium tumefaciens. After generating the insertion mutants, the mutants can be screened to identify those containing the insertion in an appropriate gene. Plants containing a single transgene insertion event at the desired gene can be crossed to generate homozygous plants for the mutation.

As will be apparent to the skilled person, a plant trait can also be modified by using the cre-lox system. A plant genome can be modified to include first and second lox sites that are then contacted with a Cre recombinase. Provided that the lox sites are in the same orientation, the intervening DNA sequence between the two sites will be excised. If the lox sites are in the opposite orientation, the intervening sequence is inverted.

The polynucleotides and polypeptides of this invention can also be expressed in a plant in the absence of an expression cassette by manipulating the activity or expression level of the endogenous gene by other means, for example, by ectopically expressing a gene by T- DNA activation tagging (Ichikawa et al. (1997) Nature 390 698-701; Kakimoto et al. (1996) Science 274: 982-985). This method entails transforming a plant with a gene tag containing multiple transcriptional enhancers and once the tag has inserted into the genome, expression of a flanking gene coding sequence becomes deregulated. In another example, the transcriptional machinery in a plant can be modified so as to increase transcription levels of a polynucleotide of the invention (See, e. g., PCT Publications WO 96/06166 and WO 98/53057 which describe the modification of the DNA binding specificity of zinc finger proteins by changing particular amino acids in the DNA binding motif).

Antisense suppression of expression

However, the recombinant DNA construct, comprising a nucleotide sequence as described above is particularly useful for sense and anti-sense suppression of expression, e. g., to down-regulate expression of a particular gene, in order to obtain a plant phenotype with improved fibre properties. That is, the nucleotide sequence of the invention, or subsequences or anti-sense sequences thereof, can be used to block expression of naturally occurring homologous nucleic acids. Varieties of traditional sense and antisense technologies are known in the art, e. g., as set forth in Lichtenstein and Nellen (1997), Antisense Technology: A Practical Approach IRL Press at Oxford University, Oxford, England. The objective of the antisense approach is to use a sequence complementary to the target gene to block its expression and create a mutant cell line or organism in which the level of a single chosen protein is selectively reduced or abolished.

For example, a reduction or elimination of expression (i. e., a "knock-out") of a gene product in a transgenic plant in order to produce a plant phenotype characterised by improved fibre properties can be obtained by introducing an antisense construct corresponding to the polypeptide of interest as a cDNA. For antisense suppression, a cDNA encoding the gene product or part thereof is arranged in reverse orientation (with respect to the coding sequence) relative to the promoter sequence in the expression vector. The introduced sequence need not be the full length cDNA or gene, and need not be identical to the cDNA or gene found in the plant type to be transformed. Typically, the antisense sequence need only be capable of hybridizing to the target gene or RNA of interest. Thus, where the introduced sequence is of shorter length, a higher degree of homology to the endogenous transcription factor sequence will be needed for effective antisense suppression. While antisense sequences of various lengths can be utilized, preferably, the introduced antisense sequence in the vector will range from 15-30 nucleotides in length, such as from 16-28 nucleotides, from 17-26 nucleotides or from 18-24 nucleotides in length, and improved antisense suppression will typically be observed as the length of the antisense sequence increases. Preferably, the length of the antisense sequence in the vector will be greater than 100 nucleotides. Transcription of an antisense construct as described results in the production of RNA molecules that are the reverse complement of mRNA molecules transcribed from the endogenous gene in the plant cell. For more elaborate descriptions of anti-sense regulation of gene expression as applied in plant cells reference is made to US Patent. No. 5,107,065, the content of which is incorporated herein in its entirety. RNA interference

Gene silencing that is induced by double-stranded RNA is commonly called RNA interference or RNAi. RNA interference is a molecular mechanism in which fragments of double-stranded ribonucleic acid (dsRNA) interfere with the expression of a particular gene that shares a homologous sequence with the dsRNA. The process that is mediated by the same cellular machinery that processes microRNA, known as the RNA-induced silencing complex (RISC). The process is initiated by the ribonuclease protein Dicer, which binds and cleaves exogenous double-stranded RNA molecules to produce double-stranded fragments of 20-25 base pairs with a few unpaired overhang bases on each end. The short double- stranded fragments produced by Dicer, called small interfering RNAs (siRNAs), are separated and integrated into the active RISC complex. If one part of an RNA transcript is targeted by an RNAi molecule or construct, the whole transcript is down-regulated.

The catalytically active components of the RISC complex are known in animals as argonaute proteins, endonucleases which mediate the siRNA-induced cleavage of the target mRNA strand. Because the fragments produced by Dicer are double-stranded, they could each in theory produce a functional siRNA; however, only one of the two strands - known as the guide strand - binds the argonaute protein and leads to gene silencing. The other anti-guide strand or passenger strand is degraded as a RISC substrate during the process of RISC activation. The strand selected as the guide tends to be the strand whose 5' end is more stable, but strand selection is not dependent on the direction in which Dicer cleaves the dsRNA before RISC incorporation.

RNA interference as used in the laboratory often involves perfectly base-paired dsRNA molecules that induce mRNA cleavage. After integration into the RISC, siRNAs base pair to their target mRNA and induce the RISC component protein argonaute to cleave the mRNA, thereby preventing it from being used as a translation template. To be stable in vitro or in vivo the sequence of a siLNA or siRNA compound need not be 100% complementary to its target nucleic acid. The fact that the siRNA compounds (and the siLNA compounds as described below) are complementary and specifically hybridisable to their target molecules simply imply that the siRNA (or siLNA) compounds bind sufficiently strong and specific to the target molecule to provide the desired interference with the normal function of the target whilst leaving the function of non-target mRNAs unaffected.

It is known that LNA monomers incorporated into oligos will induce RNA like structure of the oligo and of the hybrid that it may form. It is also shown that LNA residues will direct that structure to DNA residues incorporated towards the 3'-end of the LNA incorporation and to a lesser extend towards the 5'-end. The consequence of this is that it is possible to modify RNA strands with DNA monomers and if one or more LNA residues flank the DNA monomers they too will attain RNA structure. Therefore, DNA and LNA can replace RNA monomers and despite of that the oligo will attain an overall RNA like structure. DNA is much cheaper, easier to synthesize and more nuclease stable than RNA and such modification will therefore improve the overall use and applicability of siRNA's.

Organisms vary in their cells' ability to take up foreign dsRNA and use it in the RNAi pathway. In plants, however, the gene silencing caused by RNAi can spread from cell to cell in plants, and the effects of RNA interference are thus both systemic and heritable in plants

For more elaborate descriptions of RNAi gene suppression in plants by transcription of a dsRNA reference is made to US Pat. No. 6,506,559, US Patent Application Publication No. 2002/0168707 Al, and US patent applications Ser. No. 09/423,143 (see WO 98/53083), Ser. No. 09/127,735 (see WO 99/53050) and Ser. No. 09/084,942 (see WO 99/61631), all of which are incorporated herein by reference in their entirety.

In the particular embodiments by which the present invention is exemplified the sub- sequences or fragments in c) comprise the sequences of SEQ ID NOs: 8-14.

Construction of vectors

In general, those skilled in the art are well able to construct vectors of the present invention and design protocols for recombinant gene expression. For further details on general protocols for preparation of vectors reference is made to: Molecular Cloning: a Laboratory Manual: 2nd edition, Sambrook et al, 1989, Cold Spring Harbor Laboratory Press. The promoter used for the antisense gene may influence the level, timing, tissue, specificity, or inducibility of the antisense inhibition. Furthermore, antisense can manipulate its specificity by selecting either unique regions of the target gene or regions where it shares homology to other related genes.

Generally, suppression of a gene by RNA interference can be achieved using a recombinant DNA construct having a promoter operably linked to a DNA element comprising a sense and anti-sense element of a segment of genomic DNA or cDNA of the gene, e.g., a segment of at least about 25 nucleotides, such as at least 30, at least 40, at least 50, at least 75, at least 100, at least 200, at least 300, at least 400, at least 500, or at least 750 nucleotides, or such as at least 1 kb, such as at least 1,5 kb, at least 2 kb, at least 2.5 kb, os such as at least 3kb, where the sense and anti-sense DNA components can be directly linked or joined by an intron or artificial DNA segment that can form a loop when the transcribed RNA hybridizes to form a hairpin structure. In pertinent embodiments of the invention the nucleic acid construct, or recombinant DNA construct, further comprising a constitutive, inducible, or tissue specific promoter operably linked to said nucleotide sequence.

An example of nucleic acid construct, or recombinant DNA construct has a promoter driving the transcription of a DNA fragment from a target gene followed of an shorter sequence that are present in an inverted repeat, this together triggering the RNAi response of the target gene. Such a construct has been described by Brummel D. A. et al., Plant Journal 2003, 33, pages 793-800).

In another example, an artificial microRNA is constructed were a promoter drives the expression of an RNA molecule mimicking the function of an microRNA and the sequence setting the gene specificity is recominantly introduced, (se Nm et al, 2006. Expression of artificial microRNAs in transgenic Arabidopsis thaliana confers virus resistance. Science 2006, vol 24, No. llppl420- 1428) The microRNA can be of natrual occurrence and only overexpressed.

In a particular embodiment of the present invention the nucleic acid construct, or recombinant DNA construct, further comprises a strong constitutive promoter in front of a transcribed cassette consisting of part of the target gene followed by a plant functional intron followed by the same part of the target gene in reverse orientation, the transcribed cassette is followed by an terminator sequence. The preferred vector is of such type with one of the nucleotide sequence of the invention is inserted in inverted repeat orientation. In a presently preferred embodiment of the invention, the nucleic acid construct, or recombinant DNA construct, comprises the sequence of SEQ ID NO: 23.

The presently preferred nucleic acid construct for RNAi based approaches is a vector termed pK7GWIWG2(I). The vector is described in: Gateway vectors for Agrobacterium -mediated plants transformation, Kaπmi, M. et al., Trends In plant Sciences, VoI 7 no 5 pp 193- 195. The same basic kind of vector were earlier described in Wesley S. V. et al., Construct design for efficient, effective and high-throughput gene silencing in plants. Plant Journal 2001, 27, pages 581-590.

A person trained in the art will understand that any sequence being part of the genes, or the corresponding mRNA's presented here can be used to down regulate the levels of such mRNA. In the case the presented sequence does not represent the full mRNA, the full mRNA can be cloned with various techniques known to a person skilled in the arts , such as the techniques described in Sambrook et al..A recent resource important for finding more sequences associated with the mRNA transcripts of a populus genes is the published genome of Populυs tricocarpa and the resources descriebed in Tuskan et al 2006 (G. A Tuskan et al, 2006. The genome of Black Cottonwood, Populus tricocarpa (Torr. & Gray). Science vol 313 No. 5793, pages 1596- 1604. Transformation of plant cells

In accordance with the present invention, the method comprise the further step of transforming regenerable cells of a plant with said nucleic acid construct or recombinant DNA construct and regenerating a transgenic plant from said transformed cell. When introducing the above DNA construct or vector into a plant cell, certain considerations must be taken into account, well known to those skilled in the art. The nucleic acid to be inserted should be assembled within a construct that contains effective regulatory elements that will drive transcription, as described above. There must be available a method of transporting the construct into the cell. Once the construct is within the cell, integration into the endogenous chromosomal material either will or will not occur.

Transformation techniques, well known to those skilled in the art, may be used to introduce the DNA constructs and vectors into plant cells to produce transgenic plants, in particular transgenic trees, with modified fibre characteristics.

A person of skills in the art will realise that a wide variety of host cells may be employed as recipients for the DNA constructs and vectors according to the invention. Non-limiting examples of host cells include cells in embryonic tissue, callus tissue type I, II, and III, hypocotyls, meristem, root tissue, tissues for expression in phloem. As listed above, Agrobacterium transformation is one method widely used by those skilled in the art to transform tree species, in particular hardwood species such as poplar. Production of stable, fertile transgenic plants is now a routine in the art. Other methods, such as microprojectile or particle bombardment, electroporation, microinjection, direct DNA uptake, liposome mediated DNA uptake, or the vortexing method may be used where Agrobacterium transformation is inefficient or ineffective, for example in some gymnosperm species.

Alternatively, a combination of different techniques may be employed to enhance the efficiency of the transformation process, e.g. bombardment with Agrobacterium coated microparticles or microprojectile bombardment to induce wounding followed by co- cultivation with Agrobacterium.

It will be understood, that the particular choice of a transformation technology will be determined by its efficiency to transform certain plant species as well as the experience and preference of the person practising the invention with a particular methodology of choice. It will be apparent to the skilled person that the particular choice of a transformation system to introduce nucleic acid into plant cells is not essential to or a limitation of the invention, nor is the choice of technique for plant regeneration. Following transformation, transgenic plants are preferably selected using a dominant selectable marker incorporated into the transformation vector. Typically, such a marker will confer antibiotic or herbicide resistance on the transformed plants, and selection of transformants can be accomplished by exposing the plants to appropriate concentrations of the antibiotic or herbicide. A novel selection marker using the D-form of amino acids and based on the fact that plants can only tolerate the L-form offers a fast, efficient and environmentally friendly selection system. An interesting feature of this selection system is that it enables both selection and counter-selection.

Subsequently, a plant may be regenerated, e.g. from single cells, callus tissue or leaf discs, as is standard in the art. Almost any plant can be entirely regenerated from cells, tissues and organs of the plant. Available techniques are reviewed in Vasil et al. 1984, Cell Culture and Somatic Cell Genetics of Plants, VoI I, II and III, Laboratory Procedures.

After transformed plants are selected and grown to maturity, those plants showing a desired fibre phenotype are identified. Additionally, to confirm that the phenotype is due to changes in expression levels or activity of the polypeptide or polynucleotide disclosed herein can be determined by analyzing mRNA expression using Northern blots, RT-PCR or microarrays, or protein expression using immunoblots or Western blots or gel shift assays.

Plant species

In accordance with the invention, the present method produces a transgenic plant having altered fibre characteristics compared to its wild type plant from which it is derived. In an embodiment of the present method, the transgenic plant is a perennial plant, i.e. a plant that lives for more than two years. In a specific embodiment, the perennial plant is a woody plant which may be defined as a vascular plant that has a stem (or more than one stem) which is lignified to a high degree.

In a preferred embodiment, the woody plant is a hardwood plant, i.e. broad-leaved or angiosperm trees, which may be selected from the group consisting of acacia, eucalyptus, hornbeam, beech, mahogany, walnut, oak, ash, willow, hickory, birch, chestnut, poplar, alder, maple, sycamore, ginkgo, palm tree and sweet gum. Hardwood plants from the Salicaceae family, such as willow, poplar and aspen, including variants thereof, are of particular interest, as these two groups include fast-growing species of tree or woody shrub which are grown specifically to provide timber and bio-fuel for heating. Cellulosic grasses used for bio-energy like Switch grass and Red Canary Grass are also interesting. In further embodiments, the woody plant is softwood or a conifer which may be selected from the group consisting of cypress, Douglas fir, fir, sequoia, hemlock, cedar, juniper, larch, pine, redwood, spruce and yew. In useful embodiments, the woody plant is a fruit bearing plant which may be selected from the group consisting of apple, plum, pear, banana, orange, kiwi, lemon, cherry, grapevine and fig.

Other woody plants which may be useful in the present method may also be selected from the group consisting of cotton, bamboo and rubber plants.

DNA construct

According to a second main aspect of the invention a DNA construct, such as a recombinant DNA construct, is provided comprising at least one sequence as described above. In particular, the recombinant DNA construct may comprise a nucleotide sequence selected from the group consisting of: a) a nucleotide sequence encoding a polypeptide comprising a sequence selected from SEQ ID NO: 1-7; b) a complementary nucleotide sequence of a nucleotide sequence of a); c) a sub-sequence or fragment of a nucleotide sequence of a); d) a nucleic acid sequence being at least 60% identical to any one of the sequences in a), b) and c); and e) a nucleotide sequence which hybridizes under stringent conditions to a nucleotide sequence of a), b) or c).

In selected embodiments of the invention the nucleic acid sequence in d) is at least 65% identical to any one of the sequences in a), b) and c), such as at least 70% identical, at least 75% identical, at least 80% identical, at least 85% identical, at least 87% identical, at least 90% identical, at least 95% identical, at least 97% identical, at least 98% identical, at least 99% identical, or at least 99.5% identical to any one of the sequences in a), b) and c).

In further embodiments relating to this aspect of the invention the nucleotide sequence comprises a sequence selected from those of SEQ ID NOs: 8-14, or a complementary nucleotide sequence thereof.

Also in relation to this aspect of the invention it will be apparent that the sub-sequences or fragment in c) as described above comprises at least 15 nucleotides, such as at least 16 nucleotides, at least 17 nucleotides, at least 18 nucleotides, at least 19 nucleotides, at least 20 nucleotides, at least 21 nucleotides, at least 22 nucleotides, at least 23 nucleotides, at least 24 nucleotides, at least 25 nucleotides, e.g. at least 30 nucleotides, at least 35 nucleotides, at least 40 nucleotides, at least 45 nucleotides, at least 50 nucleotides, at least 55 nucleotides, at least 60 nucleotides, at least 65 nucleotides, at least 70 nucleotides, at least 75 nucleotides, at least 80 nucleotides, at least 85 nucleotides, at least 90 nucleotides, at least 95 nucleotides, or such as at least 100 nucleotides. In certain embodiments, the sub-sequences or fragment in c) as described above comprises at least about 150 nucleic acid residues, such as at least about 200, 250, 300, 330, 360, 375, 400, 425, 450, 460, 480, 500, 600, 700, 800 such as at least about 5 900 nucleotides or such as at least about 1 kb, 1.1 kb, 1.2 kb, 1.3 kb, 1.4 kb, 1.5 kb, 1.6 kb, 1.7 kb, 1.8 kb, 1.9 kb, 2 kb, 2.1 kb, 2.2 kb, 2.3 kb, 2.4 kb, 2.5 kb, 2.6 kb, 2.7 kb, 2.8 kb, 2.9 kb or such as at least about 3 kb.

Also, in accordance with the discussion above, the nucleotide sequence encodes a polypeptide comprising a conservatively substituted variant of a polypeptide of (a). 0 Further, the nucleotide sequence comprises a silent substitution in a nucleotide sequence.

In additional embodiments of the pertaining to this aspect of the invention, the subsequences or fragments have at least 65% sequence identity to a conserved domain of a nucleotide sequence as described above under item a), such as at least 70% identical, at least 75% identical, at least 80% identical, at least 85% identical, at least 87% identical,5 at least 90% identical, at least 95% identical, at least 97% identical, at least 98% identical, at least 99% identical, or at least 99.5% identical to a conserved domain of a nucleotide sequence as described above under item a).

In particular embodiments, the sub-sequences or fragments in c) comprise the sequences of SEQ ID NOs: 8-14. 0 In further embodiments and in accordance with the description above, the recombinant DNA construct further comprising a constitutive, inducible, or tissue specific promoter operably linked to said nucleotide sequence. In particular, the recombinant DNA construct may further comprise a strong constitutive promoter in front of a transcribed cassette consisting of part of the target gene followed by a plant functional intron followed by the same5 part of the target gene in reverse orientation as described above. Another preferred type of recombinant DNA construct has a promoter driving the transcription of a DNA fragment from a target gene followed of an shorter sequence that are present in an inverted repeat, as also explained above.

In the presently exemplified embodiments of the invention the recombinant DNA construct0 comprises the sequence of SEQ ID NO: 23.

Transgenic plants

A third aspect of the invention provides a transgenic plant comprising a recombinant polynucleotide (DNA construct) comprising a nucleotide sequence capable of altering in the plant the level of a gene product of at least one gene specifically expressed during wood formation phases. By analogy to the description above it will be understood that in one embodiment the said gene is selected for conforming to the criteria that RNAi down- regulation of the gene in a group of 3-8 transgenic plants causes:

a) an increase of 10% or more in average fibre length (AFL) or a decrease of 15% or more in average fibre length (AFL), and/or b) an increase of 10% or more in average fibre width (AFW) or a decrease of 15% or more in average fibre width (AFW), and/or c) an increase of 10% or more in maximum fibre length (maxFL) or a decrease of 15% or more in minimum fibre length (minFL), and/or d) an increase of 10% or more in maximum fibre width (maxFW) or a decrease of 15% or more in minimum fibre width (minFW),

when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photopeπod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions.

In an embodiment according to this aspect of the invention the at least one gene is further selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes: a) a difference of 5% or more in average final height (AFH) and maximum final height (MFH) and average maximum height growth rate (AMHGR) and maximum maximum height growth rate (MMHGR); and/or b) a difference of 5% or more in average final diameter (AFD)and maximum final diameter (MFD) and average diameter growth rate (ADGR) and maximum diameter coefficient (MDC); and/or c) a difference of 18% or more in average final height (AFH) and/or average final diameter (AFD) and/or average maximum height growth rate (AMHGR) and/or average diameter growth rate (ADGR); and/or d) a difference of 18% or more in maximum final height (MFH) and/or maximum final diameter (MFD) and/or maximum maximum height growth rate (MMHGR) and/or maximum diameter coefficient (MDC); when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photopeπod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions; wherein the maximum height growth rate is defined by calculating the slope of a linear function fitted over four consecutive height data points, a height growth rate value is calculated for data point 1-4, data point 2-5 etc. in a step-wise manner and the maximum height growth rate value is finally selected from the growth rate values for each plant.

According to particular embodiments of the invention the level of a gene product of at least one gene comprising a nucleotide sequence selected from the group consisting of: a) a nucleotide sequence from SEQ ID NO: 1-7; b) a nucleotide sequence being at least 60% identical to a nucleotide sequence from SEQ ID NO 1-7 c) a subsequence or fragment of a nucleotide sequence of a) or b) has been altered relative to the level found in the respective corresponding wild-type plant.

According to yet another embodiment of the invention, the transgenic plant comprises a recombinant polynucleotide (DNA construct) comprising a nucleotide sequence selected from the group consisting of: d) a nucleotide sequence comprising a sequence selected from SEQ ID NO: 1-7; e) a complementary nucleotide sequence of a nucleotide sequence of d); f) a sub-sequence or fragment of a nucleotide sequence of d) or e); g) a nucleic acid sequence being at least 60% identical to any one of the sequences in d), e) and f); and h) a nucleotide sequence which hybridizes under stringent conditions to a nucleotide sequence of d), e) or f).

In further embodiments of this aspect of the invention the nucleic acid sequence in c) or g) is at least 65% identical to any one of the sequences in a), b), d), e) or f), such as at least 70% identical, at least 75% identical, at least 80% identical, at least 85% identical, at least 87% identical, at least 90% identical, at least 95% identical, at least 97% identical, at least 98% identical, at least 99% identical, or at least 99.5% identical to any one of the sequences in a), b),d), e) or f).

As mentioned above the skilled person will realize that a variety of methods exist in the art for producing the nucleic acid sequences and polynucleotide constructs of the invention, e.g. by cloning techniques, assembly of fragments generated by solid phase synthesis. Again, the skilled person will understand, homologues of the described sequences may be isolated from other species, non-limiting examples of which include acacia, eucalyptus, hornbeam, beech, mahogany, walnut, oak, ash, hickory, birch, chestnut, alder, maple, sycamore, ginkgo, palm tree, sweet gum, cypress, Douglas fir, fir, sequoia, hemlock, cedar, juniper, larch, pine, redwood, spruce and yew, apple, plum, pear, banana, orange, kiwi, lemon, cherry, grapevine, fig, cotton, bamboo, switchgrass, red canary grass and rubber plants. Useful homologues of the described sequences may also be isolated from hardwood plants from the Salicaceae family, such as from willow, poplar or aspen.

Again, it will be apparent that the sub-sequences or fragment in c) or f) as described above comprises at least 15 nucleotides, such as at least 16 nucleotides, at least 17 nucleotides, at least 18 nucleotides, at least 19 nucleotides, at least 20 nucleotides, at least 21 nucleotides, at least 22 nucleotides, at least 23 nucleotides, at least 24 nucleotides, at least 25 nucleotides, e.g. at least 30 nucleotides, at least 35 nucleotides, at least 40 nucleotides, at least 45 nucleotides, at least 50 nucleotides, at least 55 nucleotides, at least 60 nucleotides, at least 65 nucleotides, at least 70 nucleotides, at least 75 nucleotides, at least 80 nucleotides, at least 85 nucleotides, at least 90 nucleotides, at least 95 nucleotides, or such as at least 100 nucleotides. In certain embodiments, the sub-sequences or fragment in c) or f) as described above comprises at least about 150 nucleic acid residues, such as at least about 200, 250, 300, 330, 360, 375, 400, 425, 450, 460, 480, 500, 600, 700, 800 such as at least about 900 nucleotides or such as at least about 1 kb, 1.1 kb, 1.2 kb, 1.3 kb, 1.4 kb, 1.5 kb, 1.6 kb, 1.7 kb, 1.8 kb, 1.9 kb, 2 kb, 2.1 kb, 2.2 kb, 2.3 kb, 2.4 kb, 2.5 kb, 2.6 kb, 2.7 kb, 2.8 kb, 2.9 kb or such as at least about 3 kb.

In particular, the transgenic plant according to the present invention may comprise a recombinant DNA construct comprising a nucleotide sequence which relative to the particular sequences described, comprises conservative variations altering only one, or a few amino acids in the encoded polypeptide may also be provided and used according to the present invention. Accordingly, it is within the scope of the invention to provide a transgenic plant comprising a recombinant DNA construct comprising a nucleotide sequence which encodes a polypeptide comprising a conservatively substituted variant of a polypeptide of a) or d).

Accordingly, the present invention may also provide a recombinant DNA construct, wherein the nucleotide sequence comprises a silent substitution in a nucleotide sequence, that is, the recombinant DNA construct may comprise a sequence alteration that does not change the amino acid sequence encoded by the polynucleotide.

In certain further embodiments of the invention, the sub-sequences or fragments have at least 65% sequence identity to a conserved domain of a nucleotide sequence as described above under item a), such as at least 70% identical, at least 75% identical, at least 80% identical, at least 85% identical, at least 87% identical, at least 90% identical, at least 95% identical, at least 97% identical, at least 98% identical, at least 99% identical, or at least 99.5% identical to a conserved domain of a nucleotide sequence as described above under item a) or d).

In the particular embodiments by which the present invention is exemplified the subsequences or fragments in c) comprise the sequences of SEQ ID NOs: 8-14.

In further embodiments the transgenic plant provided according to the invention comprises a recombinant polynucleotide construct which further comprises a constitutive, inducible, or tissue specific promoter operably linked to said nucleotide sequence.

In still further embodiments the recombinant polynucleotide construct further comprises a strong constitutive promoter in front of a transcribed cassette consisting of part of the target gene followed by a plant functional intron followed by the same part of the target gene in reverse orientation as described above. Another preferred type of recombinant polymucleotide construct has a promoter driving the transcription of a DNA fragment from a target gene followed of an shorter sequence that are present in an inverted repeat, as also explained above. In the particular embodiments by which the present invention is exemplified, the transgenic plant comprises a recombinant polynucleotide construct in which the subsequences or fragments in c) comprise the sequences of SEQ ID NOs: 8-14.

In a presently preferred embodiment of the invention, the transgenic plant according to the invention comprises a recombinant DNA construct comprising the sequence of SEQ ID NO: 23.

Plant species

In accordance with the present invention, the transgenic plant may be a perennial plant which preferable is a woody plant or a woody species. In a useful embodiment, the woody plant is a hardwood plant which may be selected from the group consisting of acacia, eucalyptus, hornbeam, beech, mahogany, walnut, oak, ash, willow, hickory, birch, chestnut, poplar, alder, maple, sycamore, ginkgo, a palm tree and sweet gum. Hardwood plants from the Salicaceae family, such as willow, poplar and aspen including variants thereof, are of particular interest, as these two groups include fast-growing species of tree or woody shrub which are grown specifically to provide timber and bio-fuel for heating.

In further embodiments, the woody plant is a conifer which may be selected from the group consisting of cypress, Douglas fir, fir, sequoia, hemlock, cedar, juniper, larch, pine, redwood, spruce and yew. In further embodiments, the woody plant is a conifer which may be selected from the group consisting of cypress, Douglas fir, fir, sequoia, hemlock, cedar, juniper, larch, pine, redwood, spruce and yew. In useful embodiments, the woody plant is a fruit bearing plant which may be selected from the group consisting of apple, plum, pear, banana, orange, kiwi, lemon, cherry, grapevine and fig.

The present invention extends to any plant cell of the above transgenic plants obtained by the methods described herein, and to all plant parts, including harvestable parts of a plant, seeds and propagules thereof, and plant explant or plant tissue. The present invention also encompasses a plant, a part thereof, a plant cell or a plant progeny comprising a DNA construct according to the invention. The present invention extends further to encompass the progeny of a primary transformed or transfected cell, tissue, organ or whole plant that has been produced by any of the aforementioned methods, the only requirement being that progeny exhibit the same genotypic and/or phenotypic characteristic(s) as those produced in the parent by the methods according to the invention.

In a further aspect, the invention relates to wood produced from the transgenic plant according to the invention.

In yet a further aspect the present invention provides a plant cell or a plant progeny comprising the DNA construct described above.

It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

All patent and non-patent references cited in the present application, are hereby incorporated by reference in their entirety.

The invention will now be described in further details in the following non-limiting examples.

Examples

Example 1

Identification of useful genes involved in wood formation and wood growth

1.1 Introduction

In order to find and elucidate the function of genes involved in wood formation and wood growth, an extensive gene mining program was performed, resulting in the identification of genes useful in wood industrial applications.

1.2. Materials and Methods

1.2.1 Gene Selection

The first step in this gene mining program was to select some genes from a large gene pool in order to narrow the genes to be tested for their function. The gene selection method is based on gene expression patterns as described in Hertzberg et al. (2001) and Schrader et al. (2004).

In Hertzberg et al. (2001) a study of the developing secondary xylem of poplar is described. The secondary xylem of poplar is highly organised with easily recognized and distinct boundaries between the different developmental stages. Wood formation is initiated in the vascular cambium. Cambial derivatives develop into xylem cells through the processes of division, expansion, secondary wall formation, lignification and, finally, programmed cell death.

The large physical size of the vascular meristem in trees was used to obtain samples from defined developmental stages by tangential cryo sectioning. To determine the steady state mRNA levels at specific stages during the ontogeny of wood formation in Populus tremula x tremuloides (hybrid aspen) samples of 30 μm thick sections were obtained through the wood development region and subsequently the samples were analysed using a spotted cDNA-microarray consisting of 2995 unique ESTs from hybrid aspen (Hertzberg et al, 2001).

These samples were also subsequent re-hybridized to the spotted micro array as described in Schrader et al. (2004). From these experiments, genes with a clear specific expression during the different phases of wood formation where selected (see Figure 1). Basis for this is the assumption that genes usually have their function where they are expressed. Thus, genes that are specifically expressed during the different wood formation phases such as cell-division, cell expansion and cell commitment in the cambial zone, and genes expressed during the secondary cell wall formation in the maturation zone (see Wilson, et al., 1966 for definitions), are more likely to be important for wood formation processes than any 5 randomly chosen gene. Like other plant meristems, the main function of the vascular cambium (Fig. 1, zone A) is cell division and the initiation of differentiation. Sequences expressed primarily in the meristem and in the zone of early cell expansion (Fig. 1, zone B) represent candidate genes involved in cell cycling, cell expansion, tip growth of fibres and biosynthesis of the primary cell wall. Zones A and B are also expected to express

10 genes that regulate cell fate and cell identity. Cell expansion takes place in the meristem (zone A) and in zones B and C. Genes with an expression across the zones A, B and C (Fig. 1) may therefore function in cell expansion. As soon as cell expansion is completed, the secondary cell wall is deposited in all xylem cells (zone D). The majority of genes involved in the biosynthesis of the secondary cell wall, were predicted to be found in zones C

15 (where the vessels initiate their secondary cell wall), D and E (Fig. 1). Genes strongly up- regulated in zone E (Fig. 1) include many wall-degrading enzymes required for cell wall sculpturing through final stages of the formation of pits and pores, or genes related to late phases of fibre maturation such as lignification and programmed cell death. Genes expressed in this zone also contains genes specifically involved in metabolism and

20 transport in ray cells, which as opposed to the fibres, remain alive and maintain their metabolic activity.

A large number of different genes expressed during different stages of xylem development were selected for functional genomic analysis using RNAi down regulation in transgenic 25 poplar plants. Figure 2 shows examples of expression patterns for genes that were selected and tested for their function.

In addition to this selection, genes were selected based on the meristem array gene expression experiment described in Schrader et al. (2004). In this experiment only the

30 cambial zone were sampled. However, the samples were thinner resulting in a higher resolution over the cambial meristem, i.e. one section corresponded to approximately three cell layers of the cambial zone, thus, providing near cell-specific resolution for the obtained expression profiles. From this experiment, genes with a peak within the cambial zone or having a steep change in expression over the cambial meristem (Schrader et al.

35 2004) were selected for functional genomic analysis using RNAi down regulation in transgenic poplar plants.

Subsequent to the selections based on expression patterns, the genes were screened based on gene annotations, and genes with apparently uninteresting gene annotations, such as ribosomal protein genes, were excluded. The use of careful selection of the genes to be functionally tested in a functional genomic program directed towards growth and wood properties is very beneficial in order to reduce cost and to search out to the interesting genes faster.

Although the selection of the genes, for which functions are analysed, are an important part of the discovery of genes with functions interesting for forest biotechnology in an economic efficient way, it is the actual testing of the gene function of the selected genes which is the crucial step for finding their use in industrial applications. Gene selection such as it is performed here is merely important in order to maximize the positive output of a functional genomics program (e.g. large scale testing of genes using mutants or transgenic plants/organisms) directed against certain properties/functions.

The result of the gene selection was 184 potential genes, 150 of these were finally functionally analysed, 7 genes of which were further selected for their involvement and use in changing and/or modifying the phenotype of the tree, with respect to fibre properties such as length and widths of the fibre. Examples of expression patterns from the 184 selected genes are shown in Figure 2 and Figure 3.

1.2.2 Cloning of the selected genes

Selected genes were subsequently cloned into a RNAi vector under the control of the CaMV 35S promoter (RNA interference vector, pK7GWIWG2(I)) using Gateway technology (Invitrogen USA). Two principal sets of cloning primers were used, one set was a universal primer pair binding to the vector and the poly-A tail, and the other set were gene-specific primers. The PCR product was first transferred into the pDONR vector (Invitrogen USA) and subsequently transferred into the destination vector pK7GWIWG2(I) according to manufacturers recommendations (Invitrogene USA). The sequences of the selected genes, their gene bank accession numbers and PCR primers etc. are listed in Table 1.1.

Table 1.1 Gene bank accession numbers, sequences and PCR primers etc. Table 1.1a

Table 1.1b

1.2.3 Plant transformation

CaMV 35S: Inverted repeat DNA constructs were transformed into Agrobacterium and subsequent into Hybrid aspen, Populus tremula L. x P. tremuloides Minch. Clone T89, hereafter called "poplar", was transformed and regenerated essentially as described in Nilsson et al. (1992). Approximately 6-8 independent lines were generated for each construct. One such group of transgenic trees produced using one construct is hereafter called a "construction group", e.g. different transgenic trees emanating from one construct. Each transgenic line within each construction group, e.g. KR555-2B KR555-3A, KR555-2B and so on, are different transformation events and therefore most probably have the recombinant DNA inserted into different locations in the plant genome. This makes the different lines within one construction group partly different. For example it is known that different transformation events will produce plants with different levels of gene down-regulation when using RNAi constructs of the type used here.

1.2.4 Plant growth The transgenic poplar lines were grown together with their wild type control (wt) trees, in a greenhouse under a photoperiod of 18 h and a temperature of 22°C/15°C (day/night). The plants were fertilized weekly Weibulls Rika S NPK 7-1-5 diluted 1 to 100 (final concentrations NO3, 55g/l; NH4, 29g/l; P, 12g/l; K, 56g/l; Mg 7,2g/l; S, 7,2g/l; B, 0,18g/l; Cu, 0,02g/l; Fe, 0,84g/l; Mn, 0,42g/l; Mo, 0,03g/l; Zn, 0,13g/L). The plants were grown for 8-9 weeks before harvest. During this time their height and diameter was measured 1 to 2 times per week. A number of wild type trees (typically 15-25 trees) and a number of transgenic trees comprising several construction groups (typically 6-20 construction groups) were grown in parallel in the greenhouse under the same above conditions. All comparisons between the wild type trees and construction groups are made within each growth group.

1.2.5 Sampling Two principal types of harvest and sampling were performed. One general type was for example for fibre size analysis, wood morphological analysis, gene expression analysis, wood density analysis and metabolomics analysis. And another type for dry weight measurements of bark, wood, leafs and roots.

1.2.6 Selection of Construction Groups

In the first round of growth for each group of trees with a specific gene down regulated using RNAi, i.e. a construction group, a number of the following analyses were performed: Growth measurements and fibre size (length and width) measurements,. These data were analysed in order to single out the Construction Groups that showed a phenotypic variation compared to wild type control trees.

Fiber analysis were performed on a subset of the produced construction groups, these construction groups were randomly selected, 17 construction groups from construction groups that passed the growth criterias used here and also 37 construction groups not passing the growth criteria set up here.

Based on the growth data a number of analyses and factors were performed and calculated in order to select the construction groups and thereby the genes which are possible to use for altering growth characters. Selection criteria's and methods were as described below.

Fibre measurements

Fibre measurements were performed on samples at 33 to 36 cm height of the stem. A piece of pure wood, about 1.5 mm x 1.5 mm x 15 mm was cut out from the stem piece. A maceration preparation (Franklin et al. 1945) was performed to get a macerate of single fibres from the small piece of wood. The sample was then measured using a

KajaaniFibreLab™ from Metso Automation, giving the average of fibre length, average fibre width and an estimation of the fibre cell wall thickness. The supplied computer software calculates these numbers using the below formulas according to the manufacturer.

Fibre length Average of fibre length, L(n), using true length of fibres, measured along the centreline:

where n, = number of fibres in class i, i = 1... 152, /, = (0,05*i)-0,025, I₁ - length of class i,

Fibre width

Average of fibre width, W; based on cross sectional measurements:

where n, = number of fibres in class i, i = 1... 100, w, = kw*(i-0,5), w, = width of class i, kw = width calibration factor,

Cell wall thickness

Average of cell wall thickness, CWT, based on cross sectional measurements:

where n, = number of fibres in class i, i = 1... 100, CWT₁ = kt*(i-0,5), CWT₁ = cell wall thickness of class i, kt = cell wall thickness calibration factor, Construction Groups with fibres with at least an 10% increase or decrease in fibre length or widths were selected as being effected in genes useful for modifying fibre dimension according to the selection criteria's below.

Fibre parameters selection criteria

In Table 1.2 the abbreviations used for the phenotypes used for the fibre selection criteria are listed.

Table 1.2 Abbreviations for phenotypes

Construction groups that showed a difference compared to the wild type population in any of the fibre parameters mentioned above were scored as construction groups that are altered in their growth properties and therefore the corresponding genes can be used to alter these properties.

As a 10% increase or a 15% decrease in fibre dimensions are of interest for the industry, the selection criteria below were used to select genes that can be used to altered fibre dimensions.

The fibre parameters selection criteria are as follows:

1. If construction group AFL is at least 10% higher than corresponding wildtype group AFL , or

2. If construction group AFW is at least 10% higher than corresponding wildtype group AFW, or 3. If construction group maxFL is at least 10% higher than corresponding wildtype group maxFL, or

4. If construction group maxFW is at least 10% higher than corresponding wildtype group maxFW, or 5. If construction group AFL is at least 15% lower than corresponding wildtype group

AFL, or

6. If construction group AFW is at least 15% lower than corresponding wildtype group AFW, or

7. If construction group minFL is at least 15% lower than corresponding wildtype group minFL, or

8. If construction group minFW is at least 15% lower than corresponding wildtype group minFW.

Construction groups meeting one or more of these criteria were selected.

Growth analysis

Growth During Exponential Phase

Under the above defined growth conditions, plants exhibit an exponential growth pattern (plant height) up to an approximate height of 80 cm or up to day 40 in the greenhouse. For each plant, data points of plant height within these bounds were used for fitting of an exponential function in the form of: h(t) = h_o *e^αr where h₀ is a constant (height at t = 0) and a is defined as the rate of exponential growth.

Maximum height growth rate

Another height growth rate measure (here named "Maximum height growth rate") was defined as the slope of a linear function fitted over four consecutive height data points. A height growth rate value was calculated for data point 1 - 4, data point 2 - 5 etc. in a step-wise manner, se Figure 4 for an example. A maximum growth rate defined as the maximum value, produced from step-wise linear regression analysis, for each plant was computed. The primary data for high Maximum height growth rate values from individual transformants in a construction group were checked so they were not based on bad values. From Figure 4, showing an example of a height growth curve, it can be seen that the height growth rate increases during the first part of growth then the plants reach their maximum height growth and then the growth rate declines as the plants become larger. Because these phases have different timing in different plants and there are some noise added meusering the plants our above described Maximum height growth using rate method is very useful in calculating the maximum growth speed in these conditions for the different individual trees.

Diameter Growth Under the above defined growth conditions, stem width exhibit a comparatively linear increase over time. Linear regression on diameter data was used for estimating diameter growth. d(t) = C * t + d₀ where d₀ is the initial width and c is the rate of diameter growth (slope).

Final height and diameter

The final height and diameter were also used to select altered construction groups. These values take into account both the trees growth capacity and the trees ability to start their growth when transferred from tissue culture into soil and placed in a greenhouse.

Selection parameters

Construction groups that showed a significant or pronounced increase compared to the wild type population in the above mentioned growth parameters, i.e. diameter growth rate, maximum height growth rate, final height and final diameter, were scored as Construction Groups that are altered in their growth properties, and therefore, the corresponding genes can be used to alter these properties. The selection criteria's are stated below. Two different selection levels were used, one basic level and one for constructs giving growth phenotypes of extra interest.

Growth difference selection criteria

In Table 1.2 the abbreviations used for the phenotypes used for the growth selection criteria are listed.

Table 1.2. Abbreviations for the phenotypes

The growth difference selection criteria are as follows:

1. If construction group AFH, MFH, AMHGR and MMHGR are at least 5% (or 8% in a second higher level) greater than corresponding wild type group AFH, MFH, AMHGR and MMHGR, or

2. If construction group AFD, MFD, ADGR and MDC are at least 5% (or 8% in a second higher level) greater than corresponding wild type group AFD, MFD, ADGR and MDC, or

3. If construction group AFH, AFD, AMHGR or ADGR is at least 18% (or 22% in the second higher level) greater than corresponding wild type group AFH, AFD, AMHGR or ADGR, or

4. If construction group MFH, MFD, MMHGR or MDC is at least 18% (or 22% in the second higher level) greater than corresponding wild type group MFH, MFD, MMHGR or MDC

Running a large scale functional genomics program produces a certain amount of variation and uncertainty in the data produced. In this set up variation is produced from sources such as: that the different lines within an construction group have different amounts of down regulation resulting in that 1 to all tested lines with in an construction group can show the phenotype; the variation in growth that occur during the experimental procedure due to small variations in plant status when transferring the plants from tissue culture to the greenhouse and variations based on different positions in the greenhouse during different time points during the growth cycle. These variations have to be dealt with when analysing the data. Based on these two different thresholds of increase 5% and 18% were used for selecting construction groups with increased growth. The selection criteria 1 and 2 uses an 5% increase, however this increase have to be present in all the phenotypes AFH, MFH, ATM and MTM corresponding to height growth or all the phenotypes AFD, MFD, ADC and MDC corresponding to diameter growth. In the cases that the phenotype only can be seen in some or one of the plants and only in one phenotype class, an higher 18% increase were used to select positive construction groups in order not to select construction groups based on random variations (selection criteria's 3 and 4 selecting on average values and maximum individual values respectively). These numbers were checked against the wild type data. The 18% level for filter 3 and 4 were passed by no wild type plants, e.g. no wild type plant in any of the growth groups had a more than 18% higher value than the wild type with the 2^nd highest value in any of the used growth phenotypes. The 5% level used for filter 1 and 2 produce less than 4% false positives (1 in 25 genes), e.g. randomly removing 5 wild type plants from the wild type control population and testing them for passing filters 1 and 2 and performing that for all the growth groups and repeating this 10 times gives that in 4% of the times the removed wild type plants will pass the filter. This is a very tough method to estimate the false positives, because the wild type control group is lowered with 5 plants.

Construction groups meeting one or more of these criteria were selected.

Internod length measurement

All the nodes from the FDL node and included 60 cm downwards the stem was counted and the average internode length was calculated.

1.3 Results In the following the results are presented, divided in the three overall phenotypes, i.e. increased fibre length/width and increased growth + increased fibre length/width.

1.3.1 Results from examples of the constructions groups selected with regard to the overall phenotype "increased fibre length and width".

Kajaani fibre data for specified construction group and corresponding wildtype group are presented in the below tables 1.4 to 1.11, wherein the average value of fibre length, fibre width and cell wall thickness is shown.

Construction group KR469

Construct KR469 corresponding to EST UB43DPE05 gene bank number BU822792. This gene is selected from the Schrader et al 2004 data and has its highest expression in samples 8-9 in the B series. The construction groups of KR469 contains individuals that show 14% increase of maximum fibre length compared to wild type, and 25% increase of maximum fibre width compared to wild type.

As shown in the below table 1.12, the construction group KR469 meets the fibre parameters selection criteria: (4), and the same construction group grown in a replicate experiment (construction group data set called KR469rpl) meets the fibre parameters selection criteria: (2), (3) and (4).

Table 1.4 Fibre raw data for KR469

Fibre Length Fibre Width CWT

Plant individual (mm) (qm) (qm)

KR469-1A-A 0,40 16,54 3,89

KR469-1A-B 0,36 16,57 3,97

KR469-2B-1 0,35 15,58 3,70

KR469-2B-2 0,39 17,64 4,27

KR469-3B 0,35 15,48 3,67

KR469-4A 0,37 16,57 3,93

KR469-4B 0,34 14,60 3,46

T89-1 0,35 15,83 3,79

T89-3 0,35 14,29 3,33

T89-7 0,33 14,00 3,33

T89-12 0,36 15,73 3,74

T89-14 0,35 15,62 3,74

T89-16 0,35 15,16 3,59

T89-17 0,34 14,94 3,50

T89-18 0,35 15,97 3,83

T89-19 0,37 15,92 3,73

T89-21 0,31 13,01 3,05

Table 1.5 Fibre raw data for KR469

Fibre Length Fibre Width CWT

Plant individual (mm) (qm) (qm)

KR469Rpl-lA-A 0,4 18,41 4,45

KR469Rpl-lA-B 0,31 14,37 3,49

KR469Rpl-2B 0,33 13,62 3,17

KR469Rpl-4A-l 0,36 15,54 3,72

KR469Rpl-4A-2 0,35 15,42 3,67

KR469Rpl-4B-l 0,34 14,62 3,42

KR469Rpl-3B-2 0,34 14,88 3,53

KR469Rpl-3B-l 0,33 13,87 3,31

KR469Rpl-4B-2 0,35 16,02 3,88

T89-1 0,33 13,31 3,08

T89-10 0,35 14,68 3,48 T89-12 0,35 14,02 3,24

T89-13 0,33 13,7 3,21

T89-17 0,33 13,74 3,17

T89-19 0,29 12,59 2,95

T89-20 0,32 12,69 2,89

T89-5 0,33 14,42 3,36

T89-9 0,32 12,39 2,78

Construction group KR083B

Construct KR083B correspond to EST A012P13U gene bank number AI162094. This gene is selected from the Hertzberg et al 2001 data and is up-regulated in the D zone. The construction group of KR083B show 10% increase of average fibre length compared to wildtype group and 13% increase of average fibre width compared to wild-type group. As shown in the below table 1.12, the construction group KR083B meets the fibre parameters selection criteria: (1) and (2).

Table 1.6 Fibre raw data for KR083

Fibre Length Fibre Width CWT

Plant individual (mm) (qrn) (qm)

KR083B-1B 0,36 15,61 3,71

KR083B-2A-A 0,36 15,86 3,72

KR083B-4A-B 0,37 15,93 3,76

KR083B-4B 0,36 15,47 3,59

KR083B-5B 0,35 14,9 3,52

T89-121 0,33 14,08 3,22

T89-122 0,35 14,59 3,34

T89-123 0,32 13,38 3,05

T89-125 0,33 14,22 3,24

T89-126 0,32 13,91 3,23

T89-127 0,3 12,35 2,79

T89-128 0,31 12,57 2,83

T89-129 0,34 14,49 3,32

T89-130 0,33 13,51 3,05

T89-131 0,34 14,78 3,42

Construction group KR144

Construct KR144 corresponding to EST A066P11U gene bank number AI164620. This gene is selected from the Hertzberg et al 2001 data and is up-regulated in the E zone. The construction group of KR144 show 15% increase of maximum fibre length compared to wild type and 14% increase of maximum fibre width compared to wild type. As shown in the below table 1.12, the construction group KR144 meets the fibre parameters selection criteria (3) and (4).

Table 1.7 Fibre raw data

Fibre Length Fibre Width CWT

Plant individual (mm) (u_m) (Hm)

144 IA 0,29 13,3 3,19

144 2 A 0,39 17,8 4,19

144 3 A 0,32 15, 15 3,61

144 4B 0,32 13,85 3,22

144 5B 0,34 15,01 3,58

T89 24 0,34 15,43 3,66

T89 25 0,33 14,96 3,51

T89 26 0,33 15,55 3,66

T89 27 0,33 15,3 3,56

T89 28 0,32 14,39 3,4

T89 29 0,33 14, 11 3,3

T89 30 0,31 14,08 3,27

T89 31 0,31 14, 17 3,31

T89 35 0,31 14,51 3,5

T89 36 0,33 14,79 3,43

T89 37 0,31 14, 19 3,33

T89 38 0,31 13,95 3,25

T89 39 0,33 14,62 3,46

T89 40 0,32 14,94 3,52

T89 41 0,32 14,29 3,36

Construction group KR 153

Construct KR153 corresponding to EST A078P44U gene bank number AI165206. This gene is selected from the Hertzberg et al 2001 data and has its highest expression in the C, D and E zones. The construction group of KR153 show 11% increase of average fibre width compared to wild type group, 11% increase of maximum fibre length compared to wild type and 15% increase of maximum fibre width compared to wild type. As shown in the below table 1.12, the construction group KR153Rpl meets the fibre parameters selection criteria (2), (3) and (4). Table 1.8 Fibre raw data for KR153

Fibre Length Fibre Width CWT

Plant individual (mm) (u_m) (ψn)

KR153rpl- lA-B 0,39 18, 18 4,52

KR153rpl-2A 0,34 15,76 3,83

KR153rpl-3B 0,35 16,76 4,16

KR153rpl-5B-A 0,36 15,73 3,78

KR153rpl-6A 0,36 15,3 3,65

T89-150 0,31 14,83 3,55

T89-152 0,34 14,51 3,39

T89-153 0,35 15,85 3,73

T89-154 0,32 13,61 3,19

T89-155 0,34 14,26 3,33

T89-156 0,33 14,6 3,45

T89-157 0,35 15,36 3,58

T89-158 0,34 13,95 3,28

T89-159 0,34 15,27 3,62

T89-160 0,35 15, 1 3,54

Construction group KR472 Construct KR472 correspond to EST UB52DPC06 gene bank number BU823425. This construct induces increased diameter growth and longer and wider fibres in some of the transformants. While the diameter growth is increased this is not enough to meet the specified criteria for increased growth. The fibres in this experiment are up to 40% longer and also wider.

The construction groups of KR472 were re-grown and the re-growth data show individuals that have an increase of maximum fibre length of up to 37% compared to wild type and an increase of maximum fibre width of up to 55% compared to wild type. As shown in the below table 1.12, both growth groups of construction group KR472 meet the fibre parameters selection criteria: (1), (2), (3) and (4).

This large increase in fibre dimensions using this gene makes it of extra interest for modifying fibre length and fibre width. Table 1.9a Growth raw data

Height (cm)

Days in greenhouse 21 28 30 34 37 41 44 49 50

KR472rpl-lA 38 57 66 85 100 119 131 N/A 163

KR472rpl-4A 37 56 65 84 98 116 129 N/A 158

KR472rpl-5B-l 31 52 61 83 96 114 128 N/A 153

KR472rpl-5B-2 28 47 55 74 87 109 122 N/A 152

KR472rpl-5B-3 28 49 57 76 89 108 121 N/A 149

T89-1 35 53 61 78 93 114 128 N/A 159

T89-10 32 51 59 77 93 111 126 N/A 156

T89-11 33 51 59 78 90 111 125 152 N/A

T89-12 36 52 62 81 95 117 130 N/A 157

T89-13 34 50 59 77 90 110 123 N/A 148

T89-14 34 53 61 77 88 103 116 141 N/A

T89-15 31 49 57 75 88 106 119 145 N/A

T89-16 36 54 63 81 94 113 127 149 N/A

T89-17 36 56 66 83 92 109 122 N/A 148

T89-18 30 48 57 77 89 109 123 147 N/A

T89-19 32 48 57 75 89 107 123 N/A 151

T89-2 33 50 59 76 89 110 123 147 N/A

T89-20 34 50 59 75 87 106 120 N/A 144

T89-21 33 50 56 73 85 104 117 137 N/A

T89-22 35 52 61 79 92 111 127 152 N/A

T89-23 32 49 57 75 86 104 118 138 N/A

T89-24 39 61 70 89 101 120 134 158 N/A

T89-25 35 57 66 86 100 119 131 157 N/A

T89-3 34 55 64 84 98 118 132 157 N/A

T89-4 33 52 63 81 94 112 127 151 N/A

T89-5 33 50 61 81 93 113 125 N/A 152

T89-6 34 54 62 81 94 114 127 150 N/A

T89-7 33 51 59 78 91 110 123 N/A 151

T89-8 35 51 61 76 91 112 126 153 N/A

T89-9 28 44 51 69 82 103 116 N/A 144 Table 1.9b Growth raw data

Diameter (mm)

Days in greenhouse 28 30 34 37 41 44 49 50

KR472rpl-lA 4,4 4,6 5,8 6,3 7,0 7,4 N/A 8,5

KR472rpl-4A 4,6 4,5 5,6 6,2 6,9 7,4 N/A 8,0

KR472rpl-5B-l 5,2 5,7 7,2 7, 1 8,5 9, 1 N/A 9,8

KR472rpl-5B-2 4,8 5, 1 5,9 6,7 7,6 8,3 N/A 8,9

KR472rpl-5B-3 4,6 5,3 6,4 6,8 8,3 8,8 N/A 9,8

T89-1 4, 1 4,8 5,5 6,5 6,7 7, 1 N/A 8,2

T89-10 4,4 4,4 5,3 6,3 7,4 7,6 N/A 8,3

T89-11 4,3 4,4 5,8 6,4 7,3 7,4 8,4 N/A

T89-12 4,6 5, 1 6,2 6,3 7,3 8,0 N/A 9,7

T89-13 4,9 5,2 6,3 6,7 7,3 8,2 N/A 8,5

T89-14 4,9 5,6 6,2 6,5 7,2 7,7 8,4 N/A

T89-15 4,3 4,7 5,4 7,5 6,9 7,1 7,9 N/A

T89-16 4,6 5, 1 5,8 6,7 6,9 7,5 8,2 N/A

T89-17 4,8 5,3 6,6 6,8 7, 1 7, 1 N/A 8,5

T89-18 4,0 4,9 5,5 5,9 6,7 7,3 7,9 N/A

T89-19 4,2 4,9 6,0 6,3 6,8 7, 1 N/A 8,1

T89-2 4,6 4,7 5,8 6,3 7,0 7,4 8,2 N/A

T89-20 4,6 5,0 6,2 6,8 7,7 9, 1 N/A 9,2

T89-21 4,2 4,5 5,7 6,4 6,5 7,5 7,5 N/A

T89-22 4, 1 4,4 5,5 5,9 6,8 7,2 7,8 N/A

T89-23 3,9 4,7 6,3 6,4 7,0 7,6 8,2 N/A

T89-24 5,3 5,6 7,3 7,2 8, 1 8,6 8,9 N/A

T89-25 4,3 5, 1 5,4 6,5 7,8 8, 1 8,5 N/A

T89-3 4,5 5,3 6,0 6,4 7,8 7,9 9,1 N/A

T89-4 4,8 5,3 6,0 6,8 7,2 7,7 8,4 N/A

T89-5 4,4 4,6 5,8 6,3 7, 1 7,8 N/A 8,3

T89-6 4,7 5,0 5,3 6,3 6,7 7,2 7,8 N/A

T89-7 4,4 5,1 6,3 6,9 7,6 8,0 N/A 8,2

T89-8 4,5 4,2 4,9 5,7 6,3 7, 1 7,4 N/A

T89-9 4,0 4,2 4,8 5,4 7,0 7,2 N/A 8,6 Table 1.10 Fibre raw data

Fibre Length Fibre Width CWT

Plant individual (mm) (qm) (qm)

KR472-1A- 1 0,34 14,55 3,39

KR472- 1A-2 0,33 14,45 3,46

KR472-4A- 1 0,4 17,29 4, 18

KR472-4A-2 0,34 14,47 3,39

KR472-4A-3 0,36 15, 11 3,57

KR472-5B- 1 0,48 21,45 5, 16

KR472-5B-2 0,49 22,32 5,46

T89- 1 0,35 15,83 3,79

T89-3 0,35 14,29 3,33

T89-7 0,33 14 3,33

T89-12 0,36 15,73 3,74

T89- 14 0,35 15,62 3,74

T89-16 0,35 15, 16 3,59

T89-17 0,34 14,94 3,5

T89- 18 0,35 15,97 3,83

T89-19 0,37 15,92 3,73

T89-21 0,31 13,01 3,05

Table 1.11 Fibre raw data from re-grown plants

Fibre Length Fibre Width CWT

Plant individual (mm) (qm) (U-Hl)

KR472Rpl-lA 0,36 15,73 3,81

KR472Rpl-4A 0,33 13,4 3, 14

KR472Rpl-5B-l 0,48 22,82 5,49

KR472Rpl-5B-2 0,45 22,41 5,4

KR472Rpl-5B-3 0,46 21,85 5,22

T89-1 0,33 13,31 3,08

T89-10 0,35 14,68 3,48

T89-12 0,35 14,02 3,24

T89-13 0,33 13,7 3,21

T89-17 0,33 13,74 3, 17

T89-19 0,29 12,59 2,95

T89-20 0,32 12,69 2,89

T89-5 0,33 14,42 3,36

T89-9 0,32 12,39 2,78 The table 1.12 shows the ratios of average fibre length (AFL), average fibre width (AFW), maximum fibre length (maxFL), maximum fibre width (maxFW), minimum fibre length (minFL), minimum fibre width (minFW) (e.g. Fibre Length (KR Mean / WT Mean)= AFL _Constructs _Group / AFL w._ldtype _Group and Fibre Length (KR MaX / WT MaX)= maxFL constructs _Group / maxFL wildtype Group)-

Table 1.12: Overall results of selected constructs of the overall phenotype "increased fibre length/width"

1.3.3 Results from examples of the constructions groups selected with regard to the overall phenotype "increased growth and fibre length/widtht"

The growth raw data for specified construction group and corresponding wild type group are shown in the below tables 1.13 and 1.15. Table rows contain height and diameter measurements of individuals of specified construction group and corresponding wild type group. Time of measurement, i.e. number of days in greenhouse, is shown in table header.

The Kajaani fibre data for specified construction group and corresponding wild type groups are shown in the below tables 1.14 and 1.16. The table below show the average value of fibre length, fibre width and cell wall thickness.

1.3.2 Construct KR228

Construct KR228 corresponding to EST A014P50U gene bank number AI162239. This gene is selected from the Hertzberg et al 2001 data and is gradually up-regulated from zone A to E. This construct induces increased growth and changes fibre dimensions. The maximum height growth was 19% faster comparing the fastest transgenic tree with the fastest wildtype tree. The construction group of KR228 also show 11% increase of average fibre length compared to wild type group and 12% increase of average fibre width compared to wild type group. Thus, the construct meets the Growth Filter criterion (4) and fibre parameters selection criteria: (1) and (2), as shown in the below tables 1.17 and 1.18.

Table 1.13a Growth raw data

Height (cm)

Days in greenhouse 17 21 23 25 29 30 32 35 38 43 46 50 59

KR228-1B 23 27 31 34 43 46 53 61 72 88 97 110 164

KR228-2A 29 34 39 43 52 56 62 71 81 101 113 128 160

KR228-3B-A 24 30 33 37 47 51 58 69 81 99 110 124 156

KR228-3B-B 19,5 23 25 29 38 41 47 55 66 86 97 111 142

KR228-4A 23 24 24 24 28 30 33 39 48 62 70 83 103

T89-103 27 31 33 37 45 48 52 60 72 92 105 118 149

T89-104 22 27 30 32 40 43 49 57 67 84 93 105 132

T89-106 25 27 30 33 40 42 46 54 62 79 88 102 133

T89-107 23 26 29 31 36 39 44 50 59 75 85 99 128

T89-108 24 30 33 35 42 46 51 60 71 92 103 116 146

T89-109 26 31 35 39 49 52 58 67 78 98 107 122 146

T89-110 26 31 33 37 45 47 51 60 68 84 94 106 139

T89-111 26 30 31 34 40 41 47 54 64 80 92 105 136

T89-112 27 31 36 40 50 54 60 69 80 99 110 123 155

T89-113 23 27 29 33 41 44 49 57 66 85 95 107 133

T89-114 23,5 28 32 35 41 44 50 58 68 84 94 106 137

T89-115 26 30 32 35 42 46 51 60 69 87 97 113 143

Table 1.13b Growth raw data

Diameter (mm) Days in greenhouse 21 23 25 29 30 22 35 38 42 46 50 59

KR228-1B 3,0 3,2 3,3 4,2 4,4 4,7 5,4 6,0 6,8 7,4 8, 1 9,0

KR228-2A 3,8 3,7 4,0 4,4 4,7 5,0 5,5 6, 1 7,4 7,7 8,3 9,6

KR228-3B-A 3,5 3,9 3,8 4,4 4,7 5,4 5,8 6,2 6,9 7,8 8, 1 9,5

KR228-3B-B 2.8 2,9 3,4 3,7 4,0 4,0 4,3 5, 1 6,1 6,6 7,3 8,9

KR228-4A 2.9 3, 1 3,0 2,5 3,2 3,3 3,6 3,9 4,5 5,0 5,7 7,6

T89-103 3,5 3,5 4,2 4,5 4,5 4,7 5,2 6,0 6,6 7, 1 7,6 8,7

T89-104 3,3 3,3 3,6 3,9 4,3 4,7 5,2 5,7 6,7 6,8 7,6 8,4 T89-106 3,0 3,3 3,3 4,0 4,3 5,0 5,0 5,5 6,3 7,3 7,9 9,5 T89-107 2,7 2,7 3,0 3,6 4,2 3,8 4,3 4,7 5,7 6,3 6,7 8,7 T89-108 3,3 3,2 3,6 4,2 4,4 4,4 5,1 5,4 6,5 6,9 7,1 8,5 T89-109 3,6 3,5 4,2 4,6 4,7 4,8 5,3 5,7 6,6 7,2 7,4 8,6 T89-110 3,0 3,4 3,2 3,9 4,1 4,5 5,1 5,5 6,0 6,4 7,0 9,1 T89-111 2,9 3,1 3,2 4,0 3,9 4,3 4,9 5,5 6,3 7,3 7,6 9,1 T89-112 3,5 3,8 4, 1 4,9 5,0 5,5 6,1 5,3 7,6 7,5 8,9 9,5 T89-113 3,0 3,4 3,3 4,0 4,3 4,5 5,3 5,3 5,7 6,3 6,9 8,2 T89-114 3,2 3,5 3,3 4,0 4,3 4,5 5,0 5,1 6,5 6,3 7,2 7,7 T89-115 3,3 3,2 3,6 3,9 4, 1 4,5 5,2 5,6 6,6 7, 1 7,4 8,8

Table 1.14 Fibre raw data

Fibre Length Fibre Width CWT

Plant individual (mm) (qm) (qm)

KR228-1B 0,36 16,28 3,93

KR228-2A 0,38 17,54 4,25

KR228-3B-A 0,36 16,66 3,99

KR228-3B-B 0,36 16,98 4,08

KR228-4A 0,35 15,72 3,75

T89-103 0,33 15,46 3,71

T89-107 0,34 15,88 3,75

T89-109 0,35 15,95 3,78

T89-110 0,33 14,18 3,33

T89-111 0,36 16,2 3,88

T89-112 0,33 15,15 3,56

T89-113 0,31 14,54 3,4

T89-114 0,27 11,43 2,54

T89-115 0,32 15,32 3,64

Construction group KR454

Construct KR454 corresponding to EST G100P77Y gene bank number BI130133. This gene is selected from the Schrader et al 2004 data and has step rise in expression levels over the cambial zone with low expression on the phloem side and high expression on the xylem side of the cambium, in the Hertzberg et al data the expression is highest samples B and C. This construct induces increased growth and changes fibre dimensions. The construction group of KR454 show 19% decrease of average fibre length compared to wild type group and 17% decrease of average fibre width compared to wild type group. The minimum fibre length is 22% lower compared to wild type. The construct meets the Growth Filter criteria (3) and the fibre parameters selection criteria: (5) and (7), as shown in the below tables 1.17 and 1.18.

Table 1.15 Growth raw data

Height (cm) Diameter (mm)

Days in greenhouse 18 26 33 39 47 53 65 33 39 47 53 59 65

KR454-1A-A 17 26 39 65 78 95 137 3,6 5,4 6,4 7,0 7,3 8,2

KR454-1A-B 10 19 31 57 73 90 124 4, 1 6,0 7,1 7,9 8,6 9,9

KR454-2A-A 25 43 61 94 110 129 165 5,0 6,6 7,3 8,2 8,7 10,1

KR454-2A-B 25 41 57 86 102 121 160 5,4 7, 1 7,9 8,6 9, 1 10,1

KR454-4A-B 14 23 33 58 71 90 122 3,4 4,7 5,6 6,2 7,2 7,9

T89-133 23 37 51 84 103 121 156 4,7 6,7 7,7 8,4 9, 1 9,7

T89-134 25 38 50 80 95 112 149 4,4 6,2 7, 1 7,6 7,6 8,4

T89-135 17 29 43 71 86 104 140 4,8 6,6 7,7 8,6 9, 1 9, 1

T89-136 19 31 45 72 85 103 138 4,6 5,3 6,0 6,4 7,3 7,8

T89-137 22 37 52 82 96 112 151 5,0 6,5 7,3 7,8 N/A 10,0

T89-138 21 33 47 78 94 109 140 4,9 6,0 7,0 7,8 8,4 9,0

T89-139 24 39 56 92 108 124 159 4,8 5,7 6,3 7,0 7,6 8,4

T89-140 25 41 56 88 101 115 148 4,9 6,0 6,0 6,8 7,0 7,8

T89-141 17 30 45 77 87 104 132 5,0 5,3 6,2 6,4 6,9 7,2

T89-142 24 38 54 85 99 116 146 5,3 5,9 6,3 6,6 7,6 8,3

T89-143 24 40 56 89 107 122 155 4,7 5,7 6,3 6,8 7,3 8,4

T89-144 23 37 52 76 89 107 139 4,5 5,9 6,5 6,9 7, 1 7,9

T89-146 27 43 58 84 99 116 153 4,6 6,0 6,7 7,4 7,8 8,5

T89-147 26 44 62 95 111 130 167 5,4 6,5 6,9 7,4 8,0 8,7

T89-148 21 32 47 77 91 109 146 4,2 5,4 6, 1 6,6 6,9 7,8

Table 1.16 Fibre raw data

Fibre Length Fibre Width CWT

Plant individual (mm) (Um) ( U-Hl)

KR454-1A-A 0,27 12,15 2,78

KR454-1A-B 0,29 14,05 3,29

KR454-2A-A 0,31 15,38 3,66

KR454-2A-B 0,25 12,24 2,81

KR454-4A-B 0,26 13,26 3,14

T89-133 0,37 17,35 4,23 T89-135 0,32 13,81 3,26 T89-137 0,34 14,28 3,35 T89-139 0,32 13,65 3,18 T89-140 0,33 14,05 3,28 T89-141 0,34 14,39 3,37 T89-142 0,34 14,75 3,43 T89-144 0,33 13,66 3,14 T89-146 0,33 14,64 3,49 T89-147 0,34 15,29 3,59

The below table 1.17 shows the ratios of height and diameter growth measures of specified construction group relative to corresponding wildtype group (e.g. average final height (AFH) ratio: AFH_Construction_group/AFH_Wlidtype_group)- Table contains ratios of computed growth measures AFH, AFD, AMHGR, ADC, MFH, MFD, MMHGR and MDC. (Declaration of growth measures described above).

Table 17: Overall results of selected constructs with regard to "increased growth" in the overall phenotype "increased growth and increased fibre length/width".

The table 1.18 below show the ratios of average fibre length (AFL), average fibre width (AFW), maximum fibre length (maxFL), maximum fibre width (maxFW), minimum fibre length (minFL), minimum fibre width (minFW) (e.g. Fibre Length (KR Mean / WT Mean)= AFL _{Constructlon Group} / AFL _w,|_dtyp_{e GrouP} and Fibre Length (KR Max / WT Max)= maxFL c_onstructs

Group / maxFL wildtype Group) -

Table 1.18: Overall results of selected constructs with regard to "increased fibre length/width" in the overall phenotype "increased growth and increased fibre length/width".

1.4 Discussion

Of the 54 construction groups selected for fiber measurements, 14 had wider or longer fibers and 5 had narrower or shorter fibers. There were no correlation that trees growing faster alternatively slower generally would have longer or shorter fibers respectively. For example KR454 had shorter fibers and an increased maximal height growth rate. This shows that it is hard to select which plants to measure fiber length in. However of the tested construction groups 25% showed changed fiber dimensions accordingly to the criterias set up here showing that by using the right amount of data and information for the selection of genes to be functionally analysed in a functional genomics program, in the present case directed towards growth and fibre properties, allow us to find a high number of genes that can be utilized in modifying fibre properties dimensions in plants, specifically trees.

Of all the genes tested in this program less than 18% passed the first level of selection for the growth criteria and less than 9% passed the second level of the growth criteria's set up here for genes of extra interest. Although this is only a smaller part of the genes selected to be tested, the numbers are high compared to what one would expect from a random choice of genes to be tested, showing the importance and utility for our kind of selection of genes to be tested. The foregoing example also illustrate the following: when comparing phenotypes according to single criteria, such as height or diameter, one are able to record and select genes causing strong phenotypes such as the ones selected by growth criteria filters 3 and 4. However, comparing the phenotypes according to multiple criteria, such as average final height, maximum final height, average MAXIMUM HEIGHT GROWTH RATE, and maximum MAXIMUM HEIGHT GROWTH RATE reveals that the down-regulation of the expression of some genes has a surprisingly large effect of the overall growth characteristics. As illustrated, this has allowed the identification of a subset of genes, wherein down-regulation of their expression leads to a considerable effect on plant growth. Having identified this subset of genes provides a clear advance over the state of the art and has significantly facilitated the generation and selection of promising transformation events for generation of transgenic plants with improved phenotypic traits.

When producing commercial lines using any of the different ways possible to down regulate gene expression one could produce many lines with different methods and test those for the desired properties. This could be done because different down regulation levels of the trait gene will often give different results. This can be clearly seen in the data in this example. One would then select the most promising transformation events.

References

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6. Uggla et al. 1996 Proc. Natl. Acad. Sci. USA, 1996 (93), 9282 - 9286

7. Schena et al. 1995 Science 1995 (270) 467 - 470

8. Wilson, B. F., Wodzicki, T.J. and Zhaner,R. (1966), Forest Science 12, pp 438-440

9. Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd Ed., Cold Spring Harbor, 10. Rognes T, 2001, Nucleic Acids Research, 29, 1647-1652, 1989.

11. Smith TF and Waterman MS, 1981, Journal of Molecular Biology, 147, 195-197.

12. H. Neurath and R. L. Hill, 1979, In, The Proteins, Academic Press, New York.

13. WO2004097024

14. U. S. Patent No.4,987,071 15. U. S. Patent No.5,543,508.

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18. WO2006/078431

19. Slade and Knauf, Transgenic Res. 2005 Apr; 14(2): 109-15 20. Henikoff, Till, and Comai, Plant Physiol. 2004 Jun; 135(2) :630-6.

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Oxford University, Oxford, England. 26. US Patent. No. 5,107,065

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28. US Patent Application Publication No. 2002/0168707 Al

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32. Brummel D. A. et al.. Plant Journal 2003, 33, pages 793-800

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Laboratory Procedures

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37. G.A Tuskan et al., 2006. Science vol. 313 No. 5793, pages 1596-1604.

Claims

1. A method of producing a transgenic plant having an increased fibre length and/or width compared to its wild type, comprising altering in the plant the level of a gene product of at least one gene specifically expressed during wood formation phases.

2. A method according to claim 1, wherein the one or more genes are selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes: a) an increase of 10% or more in average fibre length (AFL) or a decrease of 15% or more in average fibre length (AFL), and/or b) an increase of 10% or more in average fibre width (AFW) or a decrease of 15% or more in average fibre width (AFW), and/or c) an increase of 10% or more in maximum fibre length (maxFL) or a decrease of 15% or more in minimum fibre length (minFL), and/or d) an increase of 10% or more in maximum fibre width (maxFW) or a decrease of 15% or more in minimum fibre width (minFW),

when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photoperiod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions.

3. A method according to claim 1, wherein the at least one gene is also selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes:

a) a difference of 5% or more in average final height (AFH) and maximum final height (MFH) and average maximum height growth rate (AMHGR) and maximum maximum height growth rate (MMHGR); and/or b) a difference of 5% or more in average final diameter (AFD)and maximum final diameter (MFD) and average diameter growth rate (ADGR) and maximum diameter coefficient (MDC); and/or c) a difference of 18% or more in average final height (AFH) and/or average final diameter (AFD) and/or average maximum height growth rate (AMHGR) and/or average diameter growth rate (ADGR); and/or d) a difference of 18% or more in maximum final height (MFH) and/or maximum final diameter (MFD) and/or maximum maximum height growth rate (MMHGR) and/or maximum diameter coefficient (MDC); when comparing said group of transgenic plants grown for 8 weeks in a greenhouse under a photoperiod of 18 hours, a temperature of 22°C/15°C (day/ night) and a weekly fertilization with N 84 g/l, Pl 2g/l, K 56 g/l, with a group of wild-type plants grown under identical conditions; wherein the maximum height growth rate is defined by calculating the slope of a linear function fitted over four consecutive height data points, a height growth rate value is calculated for data point 1-4, data point 2-5 etc. in a step-wise manner and the maximum height growth rate value is finally selected from the growth rate values for each plant.

4. A method according to one of the preceding claims, comprising altering in the plant the level of a gene product of at least one gene comprising a nucleotide sequence selected from the group consisting of: a) a nucleotide sequence from SEQ ID NO 1-7; b) a nucleotide sequence being at least 60% identical to a nucleotide sequence from SEQ ID NO 1-7 c) a subsequence or fragment of a nucleotide sequence of a) or b).

5. A method according to any one of the preceding claims, comprising the step of providing a recombinant DNA construct comprising a nucleotide sequence selected from the group consisting of:

d) a nucleotide sequence comprising a sequence selected from SEQ ID NO: 1-7; e) a complementary nucleotide sequence of a nucleotide sequence of d); f) a sub-sequence or fragment of a nucleotide sequence of d) or e); g) a nucleic acid sequence being at least 60% identical to any one of the sequences in d), e) and f); and h) a nucleotide sequence which hybridizes under stringent conditions to a nucleotide sequence of d), e) or f).

6. A method according to claim 4 or 5, wherein the nucleotide sequence comprises a sequence selected from those of SEQ ID NOs: 8-14, or a complementary nucleotide sequence thereof.

7. The method according to claim 4 or 5, wherein the sub-sequence or fragment in c) or f) comprises at least 15 nucleotides.

8. The method according to any one of claims 4 to 7, wherein the nucleotide sequence

5 encodes a polypeptide comprising a conservatively substituted variant of a polypeptide of (a).

9. The method according to any one of claims 4 to 8, wherein the nucleotide sequence comprises a silent substitution in a nucleotide sequence.

10

10. The method according to any one of claims 4 to 9, wherein the sub-sequences or fragments have at least 65% sequence identity to a conserved domain of a nucleotide sequence as described in claim 3 a).

15 11. The method according to any one of claims 4 to 9, wherein the sub-sequences or fragments in c) or f) comprise the sequences of SEQ ID NOs: 8-14.

12. The method according to any one of claims 4 to 11, wherein the recombinant DNA construct further comprises a constitutive, inducible, or tissue specific promoter operably

20 linked to said nucleotide sequence.

13. The method according to any one of claims 4 to 10, wherein the recombinant DNA construct further comprises a strong constitutive promoter in front of a transcribed cassette consisting comprising a nucleotide sequence as defined in claim 4 followed by a plant

25 functional intron followed by the nucleotide sequence as defined in claim 4 in reverse orientation.

14. The method according to any one of claims 4 to 13, wherein the recombinant DNA construct comprises the sequence of SEQ ID NO: 23.

30

15. The method according to any one of claims 4 to 14, wherein the method comprising the further step of transforming regenerable cells of a plant with said recombinant DNA construct and regenerating a transgenic plant from said transformed cell.

35 16. The method according to any one of the preceding claims, wherein the transgenic plant is a perennial plant.

17. The method according to claim 16, wherein the perennial plant is a woody plant.

18. The method according to claim 17, wherein the woody plant is a hardwood plant.

19. The method according to claim 18, wherein the hardwood plant is selected from the group consisting of acacia, eucalyptus, hornbeam, beech, mahogany, walnut, oak, ash,

5 willow, hickory, birch, chestnut, poplar, alder, maple, sycamore, ginkgo, a palm tree and sweet gum.

20. The method according to claim 18 or claim 19, wherein the hardwood plant is a plant of the Salicaceae group, including variants thereof.

10

21. The method according to claim 18 or claim 19, wherein the hardwood plant is a plant of the Populus group, including variants thereof.

22. The method according to claim 16, wherein the woody plant is a conifer. 15

23. The method according to claim 22, wherein the conifer is selected from the group consisting of cypress, Douglas fir, fir, sequoia, hemlock, cedar, juniper, larch, pine, redwood, spruce and yew.

20 24. The method according to claim 16, wherein the woody plant is a fruit bearing plant.

25. The method according to claim 24, wherein the fruit bearing plant is selected from the group consisting of apple, plum, pear, banana, orange, kiwi, lemon, cherry, grapevine and fig.

25

26. The method according to claim 16, wherein the woody plant is selected from the group consisting of cotton, bamboo and rubber plants.

27. A transgenic plant comprising a recombinant polynucleotide (DNA construct)

30 comprising a nucleotide sequence capable of altering in the plant the level of a gene product of at least one gene specifically expressed during wood formation phases, wherein said gene is selected for conforming to the criteria that RNAi down-regulation of the gene in a group of 3-8 transgenic plants causes:

35 a) an increase of 10% or more in average fibre length (AFL) or a decrease of 15% or more in average fibre length (AFL), and/or b) an increase of 10% or more in average fibre width (AFW) or a decrease of 15% or more in average fibre width (AFW), and/or c) an increase of 10% or more in maximum fibre length (maxFL) or a decrease of 15% or more in minimum fibre length (minFL), and/or d) an increase of 10% or more in maximum fibre width (maxFW) or a decrease of 15% or more in minimum fibre width (minFW),

28. A transgenic plant according to claim 27, wherein said gene is further selected for conforming to the criteria that RNAi down-regulation of said gene in a group of 3-8 transgenic plants causes:

a) a difference of 5% or more in average final height (AFH) and maximum final height (MFH) and average maximum height growth rate (AMHGR) and maximum maximum height growth rate (MMHGR); and/or b) a difference of 5% or more in average final diameter (AFD)and maximum final diameter (MFD) and average diameter growth rate (ADGR) and maximum diameter coefficient (MDC); and/or c) a difference of 18% or more in average final height (AFH) and/or average final diameter (AFD) and/or average maximum height growth rate (AMHGR) and/or average diameter growth rate (ADGR); and/or d) a difference of 18% or more in maximum final height (MFH) and/or maximum final diameter (MFD) and/or maximum maximum height growth rate (MMHGR) and/or maximum diameter coefficient (MDC);

29. A transgenic plant according to claim 27 or 28, in which the level of a gene product of at least one gene comprising a nucleotide sequence selected from the group consisting of: a) a nucleotide sequence from SEQ ID NO 1-7; b) a nucleotide sequence being at least 60% identical to a nucleotide sequence from 5 SEQ ID NO 1-7 c) a subsequence or fragment of a nucleotide sequence of a) or b) is altered.

30. A transgenic plant comprising a recombinant polynucleotide (DNA construct) 10 comprising a nucleotide sequence selected from the group consisting of:

d) a nucleotide sequence encoding a polypeptide comprising a sequence selected from SEQ ID NO: 1-7; e) a complementary nucleotide sequence of a nucleotide sequence of d); 15 f) a sub-sequence or fragment of a nucleotide sequence of d) or e); g) a nucleic acid sequence being at least 60% identical to any one of the sequences in d), e) and f); and h) a nucleotide sequence which hybridizes under stringent conditions to a nucleotide sequence of d), e) or f). 20

31. The transgenic plant according to claim 30, wherein the nucleotide sequence comprising a sequence selected from those of SEQ ID NOs: 8-14, or a complementary nucleotide sequence thereof.

25 32. The transgenic plant according any one of claims 29 and 30, wherein the subsequences or fragment in b) or f) comprises at least 15 nucleotides.

33. The transgenic plant according to any one of claims 29 to 32, wherein the nucleotide sequence encoding a polypeptide comprising a conservatively substituted variant of a

30 polypeptide of (a) or d).

34. The transgenic plant according to any one of claims 29 to 33, wherein nucleotide sequence comprising a silent substitution in a nucleotide sequence.

35 35. The transgenic plant according to any one of claims 29 to 34, wherein the subsequences or fragments have at least 65% sequence identity to a conserved domain of a nucleotide sequence of a claim 29.

36. The transgenic plant according to any one of claims 29 to 35, wherein the subsequences or fragments in c) comprises the sequences of SEQ ID NOs: 8-14.

37. The transgenic plant according to any one of claims 28 to 34, wherein the recombinant 5 DNA construct further comprising a constitutive, inducible, or tissue specific promoter operably linked to said nucleotide sequence.

38. The transgenic plant to any one of claims 29 to 37, wherein the recombinant DNA construct further comprises a strong constitutive promoter in front of a transcribed cassette

10 consisting comprising a nucleotide sequence as defined in claim 4 followed by a plant functional intron followed by the nucleotide sequence as defined in claim 4 in reverse orientation.

39. The transgenic plant according to any one of claims 29 to 38, wherein the recombinant 15 DNA construct comprises the sequence of SEQ ID NO: 23.

40. The transgenic plant according to any one of claims 27 to 39, wherein said plant belongs to a woody species.

20 41. The transgenic plant according to claim 40, wherein said plant is a hardwood plant.

42. The transgenic plant according to claim 40, wherein said plant is selected from the group consisting of acacia, eucalyptus, hornbeam, beech, mahogany, walnut, oak, ash, willow, hickory, birch, chestnut, poplar, alder, maple, sycamore, ginkgo, a palm tree and

25 sweet gum.

43. The transgenic plant according to claim 40, wherein said plant is from the Populus group including variants thereof.

30 44. The transgenic plant according to claim 40, wherein said plant is from the Salicaceae groups including variants thereof.

45. The transgenic plant according to claim 40, wherein said plant is a conifer.

35 46. The transgenic plant according to claim 44, wherein said plant is selected from the group consisting of cypress, Douglas fir, fir, sequoia, hemlock, cedar, juniper, larch, pine, redwood, spruce and yew.

47. The transgenic plant according to claim 40, wherein said plant is selected from the group consisting of bamboo and rubber plants.

48. A plant cell or plant progeny of a transgenic plant according to any of claims 27 to 47. 5

49. Wood produced by a transgenic plant according to any of claims 27 to 45.

50. A DNA construct comprising at least one sequence described in claims 4 to 11.

10 51. A plant cell or plant progeny comprising the DNA construct according to claim 50.

15