Synthetic genes for plant gums and other hydroxyproline-rich proteins

Abstract

A new approach in the field of plant gums is described which presents a new solution to the production of hydroxyproline (Hyp)-rich glycoproteins (HRGPs), repetitive proline-rich proteins (RPRPs) and arabinogalactan-proteins (AGPs). The expression of synthetic genes designed from repetitive peptide sequences of such glycoproteins, including the peptide sequences of gum arabic glycoprotein (GAGP), is taught in host cells, including plant host cells.

1 - 16 . (canceled) 
     
     
         17 . A polynucleotide encoding a fusion polypeptide, the encoded fusion polypeptide comprising a first amino acid comprising Xaa-Hyp-Xaa-Hyp (SEQ ID NO: 9), wherein Xaa is an amino acid chosen from Ser and Ala, and a second amino acid comprising a fusion partner consisting of a protein which is not a gum arabic glycoprotein; wherein the Hyp residues undergo O-glycosylation exclusively with arabinogalactan polysaccharide when the fusion polypeptide is expressed in a plant cell. 
     
     
         18 . A recombinant expression vector comprising the polynucleotide according to  claim 17 . 
     
     
         19 . The expression vector of  claim 18 , further comprising a promoter operably linked to the polynucleotide. 
     
     
         20 . The expression vector of  claim 19 , wherein the promoter is a viral promoter. 
     
     
         21 . The expression vector of  claim 20 , wherein the viral promoter is selected from the group consisting of the 35S and 19S RNA promoters of cauliflower mosaic virus. 
     
     
         22 . The expression vector of  claim 19 , wherein the polynucleotide further comprises a signal sequence selected from extensin signal sequence (SEQ ID NO: 14) and tomato arabinogalactan-protein signal sequence (SEQ ID NO: 215). 
     
     
         23 . The expression vector of  claim 22 , wherein the encoded second amino acid is a reporter gene. 
     
     
         24 . A method for producing a fusion polypeptide, comprising:
 a) providing:
 i) a recombinant expression vector according to  claim 18 ; and 
 ii) a host plant cell; and 
   b) introducing said vector into said host plant cell under conditions such that the fusion polypeptide is expressed.   
     
     
         25 . The method of  claim 24 , wherein the host plant cell is growing in culture. 
     
     
         26 . The method of  claim 25 , further comprising the step of c) recovering the fusion polypeptide from the host plant cell culture. 
     
     
         27 . The method of  claim 24 , wherein the plant cell is from the plant family Leguminoseae.