The Phylogeny And Molecular Evolution Of Acc1 Gene In P Genome Within Kengyilia Yen Et J. L. Yang (Poaceae:Triticeae)

The tribe Triticeae, one of the most important groups in Poaceae, includes about 30 genera and 465 species and contains numerous diploids and polyploids.24 major basic genomes donated by diploid species have been designated and were recognized in eighteen monogenomic genera. Many basic genomes (e.g. A, S, D, Ns, E, P) in various combinations (e.g. NsXm, StH, StY, StYP, StYW, StYH) constitute polyploidy species, which accounted for about 75% of the Triticeae species. The P genome is represented in Agropyron (P), Kengyilia (StYP), Douglasdeweya (StP) and Psammopyrum (EStP).Kengyilia Yen et J. L Yang, one of the most important polyploid perennial genera in Triticeae, was established with Kengyilia gobicola as the type by Yen and J. L. Yang in 1990. All the Kengyilia species has the StYP genomes. The StY genomes were donated by Roegneria, and the P genome was originated from Agropyron. Previous studies have indicated that there were great genetic differentiations between Kengyilia species from Central Asia and the Qinghai-Tibet Plateau, which was caused by the geographic differentiation of the P genome donor. However, little is known about how does the P genome contribute to the genetic differentiation of Kengyilia and what is the differentiation mechanism of P genome in Kengyilia and Agropyron cristatum.To estimate the molecular evolution of a single-copy gene encoding plastid acetyl-CoA carboxylase (Acc1) in Kengyilia,229 Acc1 sequences were obtained from Kengyilia (13 species)、two Agropyron species (60materials) and 33 diploid species representing 17 basic genomes. Sequence diversity and phylogeny analysis suggested that:1. Kengyilia species from the Central Asia and the Qinghai-Tibet Plateau have independent origin, which result from geographical differentiation of P genome donor-A cristatum.2. A. cristatum populations, from Central Asia, East Asia, the Qinghai-Tibet Plateau and Europe, were divided into three subclades in the phylogenetic tree. Based on the Fst estimates of 0.01943-0.17588, the distribution pattern of A. cristatum might arise from the geographical isolation or hybridization. The Central Asia, contained diversity nucleotide polymorphism and high genetic differentiation, is likely to be the differentiation central of the whole A. cristatum populations. East Asia and the Qinghai-Tibet Plateau A.cristatum populations have the lowest Fst (Fst=0.0194) and the highest Nm (12.62), which is an indicative of closely genetic relationship between the two populations. The lowest differentiation degree between Central Asia and the Europe A. cristatum populations suggested that A. cristatum from Central Asia attribute to the formation of the Europe A. cristatum directly or the Europe retained more ancestral genetic information.3. Nucleotide diversity suggested that Kengyilia species from the Qinghai-Tibet Plateau have considerable ancient mutations that are fixed with historical population expansion, Kengyilia species in Central Asia undergone polyploidization bottlenecks, and sweep event or/and population expansion event occurred in the Central Asia diploid A. cristatum population and tetraploid A. cristatum.4. The Y genome of Kengyilia was grouped with diploid genus Dasypyrum (V genome). A five bp insertion existed in all of the Y-type, which is distinguished from the St genome. We thus prefer the suggestion that Y and St genomes have different diploid donor.