Characterization And Phylogenetic Analysis Of LMW-GS And Gliadin Genes In Aegilops Sect. Sitopsis Species

The low-molecular-weight glutenin subunits and gliadins are major seed storage proteins of wheat, and closely related to the wheat quality and processing properties. Their coding genes at molecular level had been extensively conducted in wheat and its wild diploid progenitors of A and D genomes. In the present study, the characterization and phylogenetic analysis of LMW-GS (low-molecular-weight glutenin subunits, LMW-GS) and gliadin genes were conducted in the Aegilops sect. sitopsis species, Aegilops longissima (2n=2x=14, S^lS^l), Aegilops. sharonensis (2n=2x=14, S^shS^sh), Aegilops searsii (2n=2x=14, S^sS^s), Aegilops bicornis (2n=2x=14, S^bS^b) and Aegilops speltoides (2n=2x=14, SS). The main results obtained were the following:1. Characterization and phylogenetic analysis of the LMW-GS genes in Aegilops sect. sitopsis speciesA total of 69 LMW-GS genes were obtained and could be divided into 5 groups based on the deduced amino acids of the N-terminal domain, in which the MENSHIPGLERP- could belong to a B genome specific gene group in wheat, while the others METSCIPSLER, METSHILSLEK-, and METSHIPSLEKSL were proved to be novel gene groups which had not been observed in the A, B, D, and G genomes, by PCR assaying. Phylogenetic analysis indicated the genes with N-terminal domain of METSCIPSLER were grouped with those from A and D genomes, and METSHIPSLEKSL- and METSHIPSLEKSL were highly homologous to the genes in the B genome. These results supported the Sitopsis, but none of the five species, should be assigned as the donors of B genome of wheat. It was also be speculated that the Ae. Speltoides was more divergent with the other 4 species.2. Characterization and Phylogenetic analysis of a-gliadin genes in Aegilops sect, sitopsis speciesForty a-gliadin genes were obtained from 3 species in the sect, sitopsis. Sequence comparison with known genes from Ae. speltoide and Ae. longissima indicated that the a-gliadin genes in Aegilops sect, sitopsis could be divided into 12 groups. The genes from Ae. speltoide were involved in 6 groups, among which 4 groups were Ae. Speltoide specific, indicating that Ae. speltoide might be divergent from other 4 species. Some a-gliadin genes in B genome from wheat were clustered with groups of group S3, groupS8, and group S6, indicating that these genes might originate from the species in the sitopsis section. Further more, group S7-1 and group S7-2 were clustered with that from A and D genomes, which was similar in LMW-GS genes.3. Characterization and Phylogenetic analysis ofγ-gliadin genes in Aegilops sect, sitopsis speciesFifty fiveγ-gliadin genes were obtained from 5 species of Aegilops sect. sitopsis. Sequence analysis showed that these genes were high similar, but not identical to the known genes. Two groups of y-gliadin genes were apparently classified based on the number of the cysteines: group 1 with 8 conserved cysteines and group 2 with an additional free cysteine in the repetitive domain which might be involved in the formation of the glutenin polymer. The phylogenetic analysis showed that the genes with 8 cysteines could be clustered into 3 sub-groups: a distinct sub-group specific to the D genome, a sub-group of B genome specific genes and that from 5 Aegilops sect, sitopsis species, indicating that sitopsis should be considered as the origin of this B-genome specific sub-group, and the 3nd sub-group of genes from species with ABD and AB genomes and sitopsis species Ae. longissima and Aesharonesis, however, it could not be concluded that which genome could be assigned to the this sub-group.The genes of group 2 from Ae.bicornis, Ae. longissima and Ae. Sharonesis were distinctly clustered from the species, indicating it was a specific sub-group. The genes from Ae.searsii and Ae. Speltoides were clustered with some genes from species with AABBDD and AABB genomes, respectively, and no A and D genome specific genes were present in the two sub-groups, indicating that these two subgroups in wheat might be B genome specific and originate from the Ae.searsii snd Ae. speltoides, respectively.