Molecular characterization of HMW-GS 1Dx3t and 1Dx4t genes from Aegilops tauschii and their potential value for wheat quality improvement

摘要

Two x-type high molecular weight glutenin subunits (HMW-GS) in Aegilops tauschii, 1Dx3 t and 1Dx4 t were identified by SDS-PAGE and MALDI-TOF-MS. Their complete coding sequences were isolated by AS-PCR. 1Dx3 t and 1Dx4 t genes consist of 2535 bp and 2508 bp and encode 845 and 836 amino acid residues, respectively. The deduced molecular masses of 1Dx3 t and 1Dx4 t gene products are 87655.26 Da and 86664.24 Da, respectively, well corresponding to the molecular masses measured by MALDI-TOF-MS. A total of 18 SNPs were identified between 1Dx3 t and 1Dx4 t. Comparing with 1Dx5 subunit, 1Dx3 t had a six amino acid insertion at 146-151 while the 1Dx4 t had a nine amino acid deletion when compared with 1Dx3 t subunit. The authenticity of the cloned 1Dx3 t and 1Dx4 t genes were confirmed by successful expression of their ORFs in E. coli. Comparison and phylogenetic tree based on the amino acid and nucleotide sequences confirmed that 1Dx3 t was most closely related to 1Dx5 subunit that is widely accepted as a superior subunit for bread-making property. The secondary structure prediction demonstrated that 1Dx3 t subunit has significantly high α-helix and β-strand contents, suggesting it might have positive effects on dough quality.