Isolation and phylogenetic analysis of novel γ-gliadin genes in genus Dasypyrum.

As the most ancient member of the wheat gluten family, the γ-gliadin genes are suitable for phylogenetic analysis among wheat and related species. Species in the grass genus Dasypyrum have been widely used for wheat cross breeding. However, the genomic relationships among Dasypyrum species have been little studied. We isolated 22 novel γ-gliadin gene sequences, among which 10 are putatively functional. The open reading frame lengths of these sequences range from 642 to 933 bp, and these putative proteins consist of five domains. Phylogenetic analyses showed that all Dasypyrum γ-gliadin gene sequences clustered in a large group; D. villosum and tetraploid D. breviaristatum γ-gliadin gene sequences clustered in a subgroup, while diploid D. breviaristatum γ-gliadin gene sequences clustered at the edge of the subgroup. All of the Dasypyrum γ-gliadin gene sequences were absent in three major T cell-stimulatory epitopes binding to HLA-DQ2/8 in celiac disease patients. Based on the phylogenetic analyses, we suggest that D. villosum and tetraploid D. breviaristatum evolved in parallel from a diploid ancestor D. breviaristatum.