Molecular phylogeny of the RPB2 gene in five Elymus species with the StH genome

Abstract

Elymus is a polyploid genus within the grass tribe (Triticeae) and is thought to have originated from the hybridization between species in other Triticeae genera. As Elymus originated from processes such as hybridization and polyploidization, it is an ideal model species for studying how these processes lead to plant diversification and speciation. However, due to the taxonomic complexity of Elymus, many of the relationships within this genus are still under investigation. This study investigates allotetraploid Elymus species with the genome from the hybridization between Pseudoroegneria (St) and Hordeum (H). Specifically, the phylogenetic relationship among five Elymus species of the StH genome, E. caninus, E. mutabilis, E. fibrosus, E. alaskanus and E. trachycaulus, and their genome donor genera, Pseudoroegneria and Hordeum, were analyzed using the second-largest subunit of RNA polymerase II (RPB2) gene. Phylogenetic analysis revealed two distinct clades. One clade was formed with the St genome sequences of Elymus and sequences from Pseudoroegneria. A second clade was formed with the H genome sequences of Elymus and sequences from Hordeum. Phylogenetic analysis also revealed a close association between E. mutabilis and E. fibrosus, as well as with H. bogdanii; indicating H. bogdanii as a possible genome donor species. Furthermore, high nucleotide diversity was found within E. caninus and E. trachycaulus. The lowest nucleotide diversity was detected within E. mutabilis. Overall, the phylogenetic analysis proved a complex and diverse evolutionary history among the five Elymus species. The study demonstrates how the hybridization between two genetically distinct genera can lead to the production of a new genus encompassing numerous species with varying levels of genetic diversity through mutations and possibly subsequent hybridizations.