Novel expansin polynucleotides, related polypeptides and methods of use

Abstract

The present invention relates to beta expansin polypeptides, nucleotide sequences encoding the same and regulatory elements and their use in altering cell wall structure in plants. Nucleic acid constructs comprising a beta expansin sequence operably linked to a promoter, or other regulatory sequence are disclosed as well as vectors, plant cells, plants, and transformed seeds containing such constructs are provided. Methods for the use of such constructs in repressing or inducing expression of a beta expansin sequences in a plant are also provided as well as methods for harvesting transgenic expansin proteins. In addition, methods are provided for inhibiting or improving cell wall structure in plants by repression or induction of expansin sequences in plants.

1 . A method of making a beta expansin protein comprising the steps of: 
 A) expressing a protein encoded by a polynucleotide in a recombinantly engineered cell, wherein the polynucleotide is selected from the group consisting of: 
 (a) a polynucleotide encoding a B4 beta expansin polypeptide of the sequence shown in SEQ ID NO:3;  
 (b) a polynucleotide which encodes the polypeptide sequence shown in SEQ ID NO:4, and  
 (c) a polynucleotide having at least 90% sequence identity with polynucleotides of (a) or (b) and having the beta expansin protein activity of altering cell wall mechanical strength;  
  said polynucleotide operably linked to a promoter; and  
   B) purifying the protein.    
     
     
         2 . A method of making a beta expansin protein comprising the steps of: 
 A) expressing a protein encoded by a polynucleotide in a plant, wherein said polynucleotide is selected from the group consisting of: 
 (a) a polynucleotide encoding a B4 beta expansin polypeptide of the sequence shown in SEQ ID NO:3;  
 (b) a polynucleotide which encodes the polypeptide sequence shown in SEQ ID NO:4;  
 (c) a polynucleotide having at least 90% sequence identity with polynucleotides of (a) or (b); and having the beta expansin protein activity of altering cell wall mechanical strength; and  
   B) purifying the protein from the plant seed or other plant parts.    
     
     
         3 . An isolated polypeptide having expansin activity of altering cell wall mechanical strength and selected from the group consisting of: 
 (a) a polypeptide comprising the amino acid sequence set forth in SEQ ID NO:4;    (b) a polypeptide encoded by a nucleotide sequence comprising the sequence set forth in SEQ ID NO:3;    (c) a polypeptide encoded by a nucleotide sequence that has at least 90% sequence identity to the sequence set forth in SEQ ID NO:3; and    (d) a polypeptide comprising an amino acid sequence having at least 90% sequence identity to the sequence set forth in SEQ ID NO:4.