Characterisation of low molecular weight glutenin subunit genes from Pseudoroegneria spicata and Pd. strigosa.

We report the characterisation of nine novel low molecular weight glutenin subunit (LMW-GS) genes from two Pseudoroegneria species, Pd. spicata and Pd. strigosa. We found that all nine LMW-GS genes possess the same primary structure shared by other published LMW-GS. Five genes encode LMW-i type subunits, three encode LMW-m type subunits and one encodes a peptide similar to B-3 hordeins of Hordeum chilense. No LMW-s type subunit genes were found in Pseudoroegneria. One subunit, PSt24-LMW-2, contains six conserved cysteine residues, and the other eight subunits all contain eight cysteine residues. We show that one cysteine residue is located in the signal peptide of PSt24-LMW-1, suggesting a mature peptide containing only seven cysteine residues. Phylogenetic analysis indicates that the LMW-GS genes from the St genome cluster together and suggests a distant relationship with LMW-GS of the A and B genomes of wheat. Slippage/unequal crossing over and illegitimate recombination are effective mechanisms for enriching variations of seed storage proteins.