Molecular cloning, heterologous expression, and phylogenetic analysis of a novel y-type HMW glutenin subunit gene from the G genome ofTriticum timopheevi

Donini, P., Li, X., Zhang, Y., Gao, L., Wang, A., Ji, K., He, Z., Appels, R., Ma, W. and Yan, Y. (2007) Molecular cloning, heterologous expression, and phylogenetic analysis of a novel y-type HMW glutenin subunit gene from the G genome ofTriticum timopheevi. Genome, 50 (12). pp. 1130-1140.

Abstract

A novel y-type high molecular weight (HMW) glutenin subunit gene from the G genome of Triticum timopheevi (2n = 4x = 28, AAGG) was isolated and characterized. Genomic DNA from accession CWI17006 was amplified and a 2200 bp fragment was obtained. Sequence analysis revealed a complete open reading frame including N- and C-terminal ends and a central repetitive domain encoding 565 amino acid residues. The molecular weight of the deduced subunit was 77 031, close to that of the x-type glutenin subunits. Its mature protein structure, however, demonstrated that it was a typical y-type HMW subunit. To our knowledge, this is the largest y-type subunit gene among Triticum genomes. The molecular structure and phylogenetic analysis assigned it to the G genome and it is the first characterized y-type HMW glutenin subunit gene from T. timopheevi. Comparative analysis and secondary structure prediction showed that the subunit possessed some unique characters, especially 2 large insertions of 45 (6 hexapeptides and a nonapeptide) and 12 (2 hexapeptides) amino acid residues that mainly contributed to its higher molecular weight and allowed more coils to be formed in its tertiary structure. Additionally, more α-helixes in the repeat domain of the subunit were found when compared with 3 other y-type subunits. We speculate that these structural characteristics improve the formation of gluten polymer. The novel subunit, expressed as a fusion protein in E. coli, moved more slowly in SDS–PAGE than the subunit Bx7, so it was designated Gy7*. As indicated in previous studies, increased size and more numerous coils and α-helixes of the repetitive domain might enhance the functional properties of HMW glutenins. Consequently, the novel Gy7* gene could have greater potential for improving wheat quality.

Publication Type:	Journal Article
Murdoch Affiliation:	Western Australian State Agricultural Biotechnology Centre
Publisher:	NRC Research Press
URI:	http://researchrepository.murdoch.edu.au/id/eprint/15584

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