Method for Increasing Seed Yield or Biomass by Expressing RNA Binding Proteins in Transgenic Plants

Abstract

The invention concerns a method for improving growth characteristics of plants by increasing activity in a plant of an RNA-binding protein which is: (i) a polypeptide having RNA-binding activity and comprising 2 or 3 RNA recognition motifs (RRMs) and a motif having at least 75% identity to motif I: PYEAAVVALPVVVKERLVRILRLGIATRYD (SEQ ID NO: 12) and/or a motif having at least 50% identity to motif II: RFDPFTGEPYKFDP (SEQ ID NO: 13); or (ii) an RBP1 polypeptide having (a) RNA-binding activity; (b) two RRM domains, (c) the following two motifs: (i) KIFVGGL (SEQ ID NO: 41); and (ii) RPRGFGF (SEQ ID NO: 42), allowing for up to three amino acid substitutions and any conservative change in the motifs; and (d) having at least 20% identity to SEQ ID NO: 15. Also provided is transgenic plants introduced with an RNA-binding protein-encoding nucleic acid having improved growth characteristics and constructs useful in the methods.

1 . A method for improving plant growth characteristics relative to a corresponding wild type plant, comprising:
 (a) introducing and expressing in a plant a nucleic acid encoding an RNA-binding protein or a homologue thereof, wherein said RNA-binding protein or homologue thereof is either:
 (i) a polypeptide having RNA-binding activity and comprising either 2 or 3 RNA recognition motifs (RRMs) and a motif having at least 75% sequence identity to motif I: PYEAAVVALPVVVKERLVRILRLGIATRYD (SEQ ID NO: 12) and/or a motif having at least 50% sequence identity to motif II: RFDPFTGEPYKFDP (SEQ ID NO: 13); or 
 (ii) an RBP1 polypeptide or homologue thereof having (a) RNA-binding activity; (b) two RRM domains, (c) the following two motifs: (i) KIFVGGL (SEQ ID NO: 41); and (ii) RPRGFGF (SEQ ID NO: 42), allowing for up to three amino acid substitutions and any conservative change in the motifs; and (d) having at least 20% sequence identity to an amino acid sequence represented by SEQ ID NO: 15; 
   and   (b) selecting a plant having improved growth characteristics relative to a corresponding wild type plant.   
     
     
         2 . The method of  claim 1 , wherein the nucleic acid encoding an RNA-binding protein or a homologue thereof comprises:
 (a) the nucleotide sequence of SEQ ID NO: 14;   (b) a nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 15; or   (c) a nucleotide sequence encoding a polypeptide having at least 80% sequence identity to the amino acid sequence of SEQ ID NO: 15.   
     
     
         3 . The method of  claim 1 , wherein the nucleic acid is operably linked to a seed-preferred promoter or a promoter capable of preferentially expressing said nucleic acid in shoots. 
     
     
         4 . The method of  claim 3 , wherein the seed-preferred promoter is prolamin promoter, or wherein the promoter capable of preferentially expressing said nucleic acid in shoots has a comparable expression profile to a beta-expansin promoter. 
     
     
         5 . The method of  claim 1 , wherein the improved plant growth characteristic is increased yield, increased seed yield, increased plant biomass, and/or increased growth rate relative to a corresponding wild type plant. 
     
     
         6 . The method of  claim 5 , wherein the increased seed yield is selected from any one or more of (i) increased seed biomass; (ii) increased number of (filled) seeds; (iii) increased seed size; (iv) increased seed volume; (v) increased harvest index; and (vi) increased thousand kernel weight (TKW). 
     
     
         7 . A plant obtained by the method of  claim 1 . 
     
     
         8 . A construct comprising:
 (i) a nucleic acid encoding an RNA-binding protein or a homologue thereof, wherein said nucleic acid comprises:
 (a) the nucleotide sequence of SEQ ID NO: 14; 
 (b) a nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 15; or 
 (c) a nucleotide sequence encoding a polypeptide having at least 80% sequence identity to the amino acid sequence of SEQ ID NO: 15; 
   (ii) one or more control sequence capable of driving expression of the nucleic acid of (i); and optionally   (iii) a transcription termination sequence.   
     
     
         9 . The construct of  claim 8 , wherein the control sequence is a promoter capable of driving expression in seed tissue or a promoter capable of driving expression in shoots. 
     
     
         10 . The construct of  claim 8 , wherein the control sequence is a prolamin promoter or a promoter having a comparable expression profile to a beta-expansin promoter. 
     
     
         11 . A plant transformed with the construct of  claim 8 . 
     
     
         12 . The plant of  claim 11 , wherein said plant is a monocotyledonous plant. 
     
     
         13 . A harvestable part or a progeny of the plant of  claim 12 , wherein said harvestable part or said progeny comprises said nucleic acid. 
     
     
         14 . The harvestable part of  claim 13 , wherein said harvestable part is a seed. 
     
     
         15 . A method for the production of a transgenic plant having improved growth characteristics relative to a corresponding wild type plant, comprising:
 (i) introducing into a plant a nucleic acid encoding an RNA-binding protein or a homologue thereof, wherein said nucleic acid comprises:
 (a) the nucleotide sequence of SEQ ID NO: 14; 
 (b) a nucleotide sequence encoding the amino acid sequence of SEQ ID NO: 15; or 
 (c) a nucleotide sequence encoding a polypeptide having at least 80% sequence identity to the amino acid sequence of SEQ ID NO: 15; 
   (ii) screening for a transgenic plant having improved growth characteristics relative to a corresponding wild type plant; and   (iii) cultivating the transgenic plant under conditions promoting plant growth and development.   
     
     
         16 . The method of  claim 15 , wherein the nucleic acid is operably linked to a seed-preferred promoter or a promoter capable of preferentially expressing said nucleic acid in shoots. 
     
     
         17 . The method of  claim 16 , wherein the seed-preferred promoter is prolamin promoter, or wherein the promoter capable of preferentially expressing said nucleic acid in shoots has a comparable expression profile to a beta-expansin promoter. 
     
     
         18 . The method of  claim 15 , further comprising obtaining a progeny plant from said transgenic plant, wherein said progeny plant comprises said nucleic acid and has having improved growth characteristics relative to a corresponding wild type plant. 
     
     
         19 . The method of  claim 15 , wherein the improved plant growth characteristic is increased yield, increased seed yield, increased plant biomass, and/or increased growth rate relative to a corresponding wild type plant. 
     
     
         20 . The method of  claim 15 , wherein the increased seed yield is selected from any one or more of (i) increased seed biomass; (ii) increased number of (filled) seeds; (iii) increased seed size; (iv) increased seed volume; (v) increased harvest index; and (vi) increased thousand kernel weight (TKW).