Molecular Characterization and Phylogenetic Analysis of Novel α-gliadin Genes from Triticum dicoccoides L.

The quality traits of Triticum dicoccoides KU-13441 (Triticum turgidum L. var. dicoccoides (AABB, 2n= 4x= 28)) were analyzed by mixograph, and the results showed that T. dicoccoides KU-13441 had desirable qualities in gluten strength and flour stirring tolerance. Subsequently, seventeen novel full-ORF α-gliadin genes and thirty-five pseudogenes were cloned and sequenced from T. dicoccoides KU-13441. Among the 17 novel full-ORF α-gliadin genes, the putative proteins of Gli2-TD-44 and Gli2-TD-46 contained an extra cysteine residue, located in the first nonrepetitive region and N-terminal repetitive domain, respectively, rather than in the second nonrepetitive region like other α-gliadins. Prokaryotic expression analysis and western-blotting indicated that these two α-gliadin genes could be successfully expressed under the control of T7 promoter. According to the varying numbers of 4 typical coeliac disease toxic peptides and glutamine residues in the two ployglutamine domains among the 17 α-gliadins, Gli2-TD-39, Gli2-TD-46 and Gli2-TD-47 genes were assigned to sub-genome B and other 14 genes were assigned to sub-genome A. Phylogenetic analysis including two S-genome species, Aegilops longissima (Sl) and Aegilops speltoides (S) revealed that the α-gliadin sequences of the B genome in T. dicoccoides had closer genetic relationship with those from Ae. speltoides. This implies that Ae. speltoides might participate in the origin of wheat B genome.