Molecular characterization of four HMW glutenin genes from Heteranthelium piliferum C. E. Hubbard and Henrardia persica (Banks et Solander) Hochstetter

High molecular weight (HMW) glutenin genes Qy and Oy were isolated and characterized. Compared with previously reported HMW genes, they showed modifications in all domains. Qy genes had an extra glutamine and 105 residues in the N terminal, two irregular tandem repeats of P–GQQGQQVYYPTAPQQ in the repetitive domain, and had the same short peptide LAAQLPAMCRLE as in x-type genes in the C-terminal. Besides these modifications, the 11?aa peptides, GSYYPGQASPQQ, conserved in the repetitive domain in all genes, were absent in Qy. Oy genes with 103 residues, had the short IPTLLS peptide found in x-type genes in the N terminal, and had unique tandem repeats of PGQGQ-RQQGYYPTSQQQ and GQQGQQ in the repetitive domain, and shared the short peptide LAAQLPAMCRLE with those of x-type genes in the C-terminal. Three of four y gene ORFs were successfully expressed in bacteria. In the phylogenetic tree based on the N- and C-terminal sequences, Qy and Oy genes clustered with y and x genes, respectively. This suggested that genes Qy and Oy were not pure y genes, but also had some characteristics of x genes. These unique structures provide new information for understanding the origin and evolution of x and y genes as well as wheat quality improvement.