Analysis of HMW glutenin subunits and their coding sequences in two diploid Aegilops species

Abstract

Considerable progress has been made in understanding the structure, function and genetic regulation of high-molecular-weight (HMW) glutenin subunits in hexaploid wheat. In contrast, less is known about these types of proteins in wheat related species. In this paper, we report the analysis of HMW glutenin subunits and their coding sequences in two diploid Aegilops species, Aegilops umbellulata (UU) and Aegilops caudata (CC). SDS-PAGE analysis demonstrated that, for each of the four Ae. umbellulata accessions, there were two HMW glutenin subunits (designated here as 1Ux and 1Uy) with electrophoretic mobilities comparable to those of the x- and y-type subunits encoded by the Glu-D1 locus, respectively. In our previous study involving multiple accessions of Ae. caudata, two HMW glutenin subunits (designated as 1Cx and 1Cy) with electrophoretic mobilities similar to those of the subunits controlled by the Glu-D1 locus were also detected. These results indicate that the U genome of Ae. umbellulata and the C genome of Ae. caudata encode HMW glutenin subunits that may be structurally similar to those specified by the D genome. The complete open reading frames (ORFs) coding for x- and y-type HMW glutenin subunits in the two diploid species were cloned and sequenced. Analysis of deduced amino acid sequences revealed that the primary structures of the x- and y-type HMW glutenin subunits of the two Aegilops species were similar to those of previously published HMW glutenin subunits. Bacterial expression of modified ORFs, in which the coding sequence for the signal peptide was removed, gave rise to proteins with electrophoretic mobilities identical to those of HMW glutenin subunits extracted from seeds, indicating that upon seed maturation the signal peptide is removed from the HMW glutenin subunit in the two species. Phylogenetic analysis showed that 1Ux and 1Cx subunits were most closely related to the 1Dx type subunit encoded by the Glu-D1 locus. The 1Uy subunit possessed a higher level of homology to the 1Dy-type subunit compared with the 1Cy subunit. In conclusion, our study suggests that the Glu-U1 locus of Ae. umbellulata and the Glu-C1 locus of Ae. caudata specify the expression of HMW glutenin subunits in a manner similar to the Glu-D1 locus. Consequently, HMW glutenin subunits from the two diploid species may have potential value in improving the processing properties of hexaploid wheat varieties.

Exploration of Triticeae seed storage proteins for improvement of wheat end-product quality

“…Ae. umbellulata HMW-GSs have been studied (Brown et al 1979, Lawrence and and sequenced (Liu et al 2003). Our studies on Ae.…”

“…caudata and Ae. cylindrica HMW-GS diversity (Wan et al 2000, Farkhari et al 2007) and sequence (Liu et al 2003, Wan et al 2002 have been determined and show similarity to wheat. HMW-GSs have also been sequenced from Ae.…”

Molecular characterization of a novel HMW glutenin subunit Dx2.3*tfromAegilops tauschii

“…Although the size of N-and C-terminal domains is highly conserved in either x-and y-type subunits, the repetitive domain size is usually variable. For instance, the repetitive domain of 1Dx2.2* from 1Ux subunit from Aegilops umbellulata is much larger than those of other reported x-type subunits (Liu et al 2003). Analysis indicates that the extra section in 1Dx2.2* contains 111 amino acid residues (Liu et al 2003).…”

The Chinese bread wheat cultivar Xiaoyanmai 7 harbours genes encoding a pair of novel high-molecular-weight glutenin subunits inherited from cereal rye

“…The complete open reading frame (ORF) of each HMW-GS gene was amplified from this DNA by using the degenerate primer pair 5 0 -ATGGCTAA GCGGC/TTA/GGTCCTCTTTG and 5 0 -CTATCACTGGCTG/ AGCCGACAATGCG (Liu et al 2003). Polymerase chain reactions (PCRs) were conducted using high-fidelity DNA polymerase KOD Plus (TOYOBO, Osaka, Japan).…”