Sucrose-binding proteins

Abstract

A cDNA encoding a plant sucrose-binding protein (SBP) is provided, together with modified SBPs having enhanced sucrose uptake activity in a yeast assay system. Nucleic acid vectors, transgenic cells and transgenic plants having modified sucrose uptake activity are also provided. The invention also relates to promoter sequences useful for controlling expression of transgenes in plants, including SBP transgenes.

1 . A modified plant sucrose binding protein wherein the modified sucrose binding protein has a modified amino acid sequence compared to a corresponding wild-type sucrose binding protein, and wherein expression of the modified sucrose binding protein in a yeast assay system confers enhanced sucrose compared to the corresponding wild-type sucrose binding protein.  
     
     
         2 . A modified plant sucrose binding protein according to  claim 1  wherein the modified sucrose binding protein enhances sucrose uptake in the yeast assay system by at least 10% compared to the wild-type sucrose binding protein.  
     
     
         3 . A modified plant sucrose binding protein according to  claim 1  wherein the modified sucrose binding protein enhances sucrose uptake in the yeast assay system by at least 25% compared to the wild-type sucrose binding protein.  
     
     
         4 . A modified plant sucrose binding protein according to  claim 1  wherein the modified amino acid sequence comprises a C-terminal truncation compared to the wild-type sucrose binding protein.  
     
     
         5 . A modified plant sucrose binding protein according to  claim 4  wherein the C-terminal truncation results in removal of between 10 and 100 amino acids.  
     
     
         6 . A modified plant sucrose binding protein, wherein the corresponding wild-type sucrose binding protein is selected from the group consisting of SBP1 and SBP2.  
     
     
         7 . A modified plant sucrose binding protein according to  claim 6  wherein the protein has an amino acid sequence selected from the group consisting of Seq. I.D. Nos. 2 and 4.  
     
     
         8 . A nucleic acid molecule encoding a modified plant sucrose binding protein according to  claim 1 .  
     
     
         9 . A vector comprising a nucleic acid molecule according to  claim 8 .  
     
     
         10 . A transgenic plant expressing a modified plant sucrose binding protein according to  claim 1 .  
     
     
         11 . A nucleic acid molecule encoding a modified sucrose binding protein according to  claim 6 .  
     
     
         12 . A transgenic plant expressing a modified plant sucrose binding protein according to  claim 6 .  
     
     
         13 . An isolated nucleic acid molecule encoding a plant sucrose binding protein, wherein the protein comprises an amino acid sequence selected from the group consisting of: 
 (a) the amino acid sequence set forth in Seq. I.D. No. 3;    (b) the amino acid sequence set forth in Seq. I.D. No. 4;    (c) amino acid sequences having at least 70% sequence identity with the amino acid sequence of (a) or (b); and    (d) amino acid sequences having at least 90% sequence identity with the amino acid sequence of (a) or (b).    
     
     
         14 . A recombinant expression cassette comprising a promoter sequence operably linked to a nucleic acid molecule according to  claim 13 .  
     
     
         15 . A transgenic plant comprising a recombinant expression cassette according to  claim 14 .  
     
     
         16 . A recombinant nucleic acid molecule comprising a promoter sequence operably linked to a nucleic acid sequence, wherein the promoter sequence comprises a SBP1 or SBP2 promoter.  
     
     
         17 . A recombinant nucleic acid molecule according to  claim 16  wherein the promoter sequence comprises at least 25 consecutive nucleotides of a sequence selected from the group consisting of: 
 (a) Seq. I.D. No. 7; and  
 (b) Seq. I.D. No. 8.  
 
     
     
         18 . A recombinant nucleic acid molecule according to  claim 17  wherein the nucleic acid sequence encodes a plant sucrose binding protein.  
     
     
         19 . A transgenic plant comprising a recombinant nucleic acid molecule according to  claim 17 .  
     
     
         20 . A transgenic plant comprising a recombinant nucleic acid molecule according to  claim 18.