Molecular diversity and relationship of Elymus species

Abstract

Classification of the tribe Triticeae has been a longstanding problem, especially the treatment of the genus Elymus. The taxonomy of Elymus is extremely complex because of the huge morphological variation within and between species. Previous studies suggested that the StH genome Elymus species originated from Pseudoroegneria ( St ) and Hordeum ( H ). In this study, we have conducted the phylogenetic analysis of Elymus species with one nuclear and two chloroplast DNA sequence data sets. Chloroplast data further supports that Pseudoroegneria as the maternal donor of the tetraploid Elymus St genome. This paper is also the first report microsatellites in the chloroplast trnS[tRNA-ser (UGA)]-psbC[spII44kd protein] region, which is highly conserved (TGAAAGAAA).

The nuclear RPB2 gene was used to examine the nuclear diversity of tetraploid Elymus and their diploid donor. The results indicated that the RPB2 gene may evolve faster in the polyploid species than in diploid. This study found a 39bp MITE stowaway element insertion in the region of the RPB2 gene for all tetraploid Elymus St genome species and also the diploid Pseudoroegneria spicata and P. stipifolia St genomes. The sequences on the 3'- end are highly conserved, with AGTA in all sequences but 10339 ( E. fibrosis ), in which the AGTA is replaced with AGAA. The 5'-end sequence of GGTA is changed to AGTA or deleted, resulting in Stowaway excition in the H genome of Elymus species. The three transposable element indels have occurred prior to polyploidization, and shaped the homoelogous RPB2 loci in St and H genome of Elymus species.