Nucleic Acid Molecules Encoding Plant Proteins in the C3HC4 Family and Methods for the Alteration of Plant Cellulose And Lignin Content

Abstract

Polynucleotides, nucleic acid constructs, and methods are disclosed for the modification of cellulose and/or lignin content in plant tissues. Plants are genetically engineered with a gene encoding a C3HC4 protein, which leads to increased cellulose content when over-expressed in the plant vascular system. Plant transformants harboring the C3HC4 protein gene show increased content of cellulose and/or decreased lignin content, traits that are thought to improve hardwood trees for cellulose extraction during pulping and papermaking.

1 . An isolated nucleic acid sequence comprising a sequence selected from the group consisting of:
 (a) a nucleic acid which is an allelic variant or alternative splice variant of the nucleic acid sequence set forth in SEQ ID NO:1, said allelic variant or alternative splice variant encoding a C3HC4 polypeptide amino acid sequence which is at least 85% or more identical to SEQ ID NO: 2, the over-expression of which results in an increase in the cellulose content and/or in a decrease in the lignin content of a plant, said C3HC4 polypeptide comprising a C3HC4 consensus motif; and   (b) a nucleic acid sequence which has at least 50%, 60%, 70%, 75%, 80%, 85%, 90% or more sequence identity to SEQ ID NO:1 and which codes for a C3HC4 polypeptide that, when overexpressed, results in an increase in the cellulose content and/or in a decrease in the lignin content of a plant, said C3HC4 polypeptide comprising a C3HC4 consensus motif.   
     
     
         2 . An isolated C3HC4 protein selected from the group consisting of:
 (a) a polypeptide with an amino acid sequence comprising a C3HC4 consensus motif and having at least 85% or more sequence identity to the amino acid sequence set forth in SEQ ID NO:2, the over-expression of which results in an increase in the cellulose content and/or in a decrease in the lignin content of a plant; and   (b) a variant of the polypeptide set forth in SEQ ID NO:2, the over-expression of which results in an increase in the cellulose content and/or in a decrease in the lignin content of a plant, said C3HC4 polypeptide comprising a C3HC4 consensus motif.   
     
     
         3 . A nucleic acid construct comprising the isolated nucleic acid sequence of  claim 1  operably linked to one or more suitable promoters that drive the expression of the nucleic acid sequence. 
     
     
         4 . The nucleic acid construct of  claim 3 , wherein the promoter is a xylem-preferred promoter. 
     
     
         5 . The nucleic acid construct of  claim 4 , wherein said xylem-preferred promoter is selected from the group consisting of TUB gene promoter, SuSy gene promoter, COMT gene promoter, and C4H gene promoter. 
     
     
         6 . A plant cell comprising the nucleic acid construct of  claim 3 . 
     
     
         7 . A transgenic plant generated from the plant cell of  claim 6 , wherein said plant has altered cellulose and/or lignin content compared to a non-transgenic plant of the same species. 
     
     
         8 . The plant cell of  claim 6 , wherein said promoter is a xylem-preferred promoter. 
     
     
         9 . The plant cell of  claim 8 , wherein said xylem-preferred promoter is selected from the group consisting of TUB gene promoter, SuSy gene promoter, COMT gene promoter, and C4H gene promoter. 
     
     
         10 . The transgenic plant of  claim 7 , wherein said plant is a dicotyledon or monocotyledon plant. 
     
     
         11 . (canceled) 
     
     
         12 . The transgenic plant of  claim 7 , wherein said plant is a gymnosperm. 
     
     
         13 . The transgenic plant of  claim 7 , wherein said plant is a hardwood tree. 
     
     
         14 . The transgenic plant of  claim 13 , wherein said hardwood tree is an  Eucalyptus  or  Populus  plant. 
     
     
         15 . (canceled) 
     
     
         16 . The transgenic plant of  claim 10 , wherein said plant is a  Pinus  plant. 
     
     
         17 . A part of the transgenic plant of  claim 7  selected from the group consisting of a leaf, a stem, a flower, an ovary, a fruit, a seed and a callus, said part comprising said nucleic acid construct. 
     
     
         18 . Progeny of the transgenic plant of  claim 7 , said progeny comprising said nucleic acid construct. 
     
     
         19 . The progeny of  claim 18 , wherein said progeny is a hybrid plant. 
     
     
         20 . A method for altering the cellulose and/or lignin content in a plant, comprising
 (a) introducing into an isolated plant cell a nucleic acid construct comprising the nucleic acid sequence of  claim 1  operably linked to one or more suitable promoters that drive the expression of the nucleic acid sequence; and   (b) culturing said plant cell under conditions that promote growth of a plant, wherein said plant over-expresses the C3HC4 protein and has increased cellulose and/or reduced lignin content compared to a non-transgenic plant of the same species.   
     
     
         21 . The method of  claim 20 , wherein the promoter is a xylem-preferred promoter. 
     
     
         22 . The method of  claim 21 , wherein the xylem-preferred promoter is selected from the group consisting of TUB gene promoter, SuSy gene promoter, COMT gene promoter, and C4H gene promoter.