Characterization and classification of <i>γ</i> -gliadin multigene sequences from <i>Aegilops</i> section <i>Sitopsis</i>

The most abundant seed storage proteins of wheat are gliadins and glutenins. Gliadins, including α/β, γ and ω types, are normally monomeric proteins and account for about 50% of the gluten proteins. In this study, 55 sequences of γ -gliadin genes were obtained from species of Sitopsis section, the deduced B genome donors of wheat. Despite the high sequence similarities to the known γ -gliadin genes, extensive variations were also found. Using the extensive sequence information deposited in database and obtained in this study, a comprehensive classification of the γ -gliadin multigene families were performed based on the primary structures and phylogenic analysis. All the γ -gliadin genes analyzed could be divided into 2 types, which contain 8 and 9 cysteines, respectively. Type I (with 8 cysteines) and type II (with 9 cysteines) are further classified to 7 and 4 groups, respectively, and several subgroups are also identified. The genes derived from A, B and D genomes of common wheat were clustered distinctly, indicating that there was apparent genomic specificity in γ -gliadins genes. Besides the high homology between γ -gliadin genes from Sitopsis species and B genome of wheat, some unique groups or subgroups were also identified in Sitopsis section, suggesting that it could be considered as a valuable source of γ -gliadin genes. The comparison of deduced primary structures of each group and/or subgroup was conducted, from which their evolution and quality properties were also speculated.