Evolutionary Dynamics Of The CHS Gene In The P Genomes Of Triticeae

The tribe Triticeae, including about 500 species, is one of the most important group in Poaceae. It not only contains some of the world’s most important cereal, such as wheat (Triticum aestivum L.)、rye (Secale cereal L.) and barley (Hordeum vulgare L.), but also includes a significant number of important forage grasses. It also contains annual species and perennial species. Therefore, studying the evolution history of the Triticeae, would point to wild taxa that may serve as sources of novel gene pool.Triticeae consists of numerous diploids and polyploids, and polyploidy leads to the lineages of at least 70% of the species within Triticeae are polyploids. According to the system of genome classifications, the main diploid genera includes Australopyrum, Agropyron, Dasypyrum, Heteranthelium, Hordeum, Psathyrostachys, Pseudoroegneria and so on, while the polyploidy genera includes Kengyilia, Douglasdeweya, Leymus. Agropyron, Kengyilia and the Douglasdeweya are the diploid or polyploids, which contains P genome. To investigate the evolutionary dynamics of the CHS gene in species (Agropyron, Kengyilia and the Douglasdeweya) contains the P genome, the sequences from CHS gene of 12 species in Kengyilia (StYP), two species in Agropyron (P), one species in Douglasdeweya and 8 diploid (Australopyrum, Dasypyrum, Heteranthelium, Hordeum, Pasthyrostachys, Pseudoroegneria, Lophopyrum and Agropyron) species were analysised. Sequences diversity patterns and genealogical analysis suggested that:1. To analysis the Neighbor-Joining tree, polymorphism and genetic distances and Fst datas of the Agropyron from the four groups, it shows genetic differentiation obviously exists between the four populations, and Central Asia may be the diversity distribution center of Agropyron species.2. The dn/ds data shows that Agropyron from the Qinghai-Tibet Plateau group retains population expansion history of ancestral genetic imprinting, helps to CHS to response to the environmental factor, such as high UV irradiation, high altitude.3. In the Neighbor-Joining tree, the Kengyilia species of central Asia and the Qinghai-Tibet Plateau groups were clustered with the local Agropyron, It indicates that the geographic genetic differentiation may happened between the Qinghai-Tibet plateau and the Central Asia area of Kengyilia. they maybe origined independently in the two groups. CHS gene in the Kengyilia from the central Asia and the Qinghai-Tibet plateau have different evolutionary potential, the Kengyilia species from qinghai-tibet plateau affected by polyploidization genetic bottlenecks, and the Kengyilia species from central Asia may get more genetic materials of Agropyron species by repeated Hybridization events, and increased the genetic diversity of the Kengyilia species from the central Asia.4. To analysis the phylogenetic ralationships among the three genus, Agropyron, the results suggests that the relationships between Kengyilia and Douglasdeweya is closely, and Ag. cristatum from central Asia may donated the P genome to D. deweyi.