Cloning and Localization of α-Gliadin Genes from Common Wheat and Aegilops tauschii and Their Molecular Evolution

Abstract

Abstract Gliadins are in high polymorphism and stable inheritance in common wheat ( Triticum aestivum L.). It not only has a close relationship with wheat quality but also acts as an index in researches on genetic diversity and evolution of wheat. In this study, 7 novel α-gliadin genes were cloned from common wheat (cv. Yumai 34 and Yannong 19) and Aegilops tauschii (T9, T197, T48, T176, and T17) using a PCR-based strategy, which were designated Gli-YM34, Gli-YN19, Gli-T9, Gli-T197, Gli-T48, Gli-T176, and Gli-T17. The open reading frames of these genes ranged from 846 to 891 bp in length, which encoded 282–297 amino acid residues. Comparative analysis showed that all the genes isolated had typical structural characters of α-gliadin genes reported previously. Particularly, Gli-YM34 and Gli-YN19 from common wheat might have a positive effect on dough quality for the presence of an additional cysteine residue. Both of them were located on the Gli-D2 locus on the chromosome 6D based on analyses of the 4 T-cell epitopes, average length of polyglutamine domain, and the nullisomic–tetrasomic lines of Chinese Spring, and they were highly homologous to the α-gliadin genes from Ae. tauschii. The sequences of 4 typical α-gliadin genes were compared with those of 10 published α-gliadin genes, and 21 single nucleotide polymorphisms (SNPs) and a 9 bp deletion were detected. Based on the neighbor-jointing unrooted phylogene tree of 39 storage protein genes from different Triticum species, the α-gliadin genes showed a close relationship with LMW-GS genes, and their divergence occurred 43.69 million years ago. There was little homology between α-gliadin genes and HMW-GS genes/ω-gliadin genes, and their divergence occurred 73.72 million years ago.