Characterization and Classification of gamma-Gliadin Multigene Sequences from Aegilops Section Sitopsis

The most abundant seed storage proteins of wheat are gliadins and glutenins. Gliadins, including alpha/beta, gamma and omega types, are normally monomeric proteins and account for about 50% of the gluten proteins. In this study, 55 sequences of gamma-gliadin genes were obtained from species of Sitopsis section, the deduced B genome donors of wheat. Despite the high sequence similarities to the known gamma-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 gamma-gliadin multigene families were performed based on the primary structures and phylogenic analysis. All the gamma-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 gamma-gliadins genes. Besides the high homology between gamma-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 gamma-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