A novel high molecular weight glutenin subunit from Australopyrum retrofractum.

We describe the sequence of a gene encoding a high molecular weight glutenin subunit (HMW-GS) expressed in the endosperm of the wheat relative Australopyrum retrofractum. Although the subunit has a similar primary structure to that HMW-GS genes present in other Triticeae species, its N-terminal domain is shorter, its central repetitive domain includes a unique dodecameric motif, and its C-terminal domain contain an extra cysteine residue. A phylogenetic analysis showed that the Glu-W1 gene is neither a true x- nor a true y-type subunit, although it is more closely related to the y-type genes present in the K and E genomes than to any other published HMW-GS gene. All these results indicated that this novel subunit may undergo a special evolutionary process different from other Triticeae species. A flour supplementation experiment showed that the Glu-W1 subunit has a negative effect on dough quality, which might be the result of interaction between the two closely placed cysteine residues in the C-terminal region.