Tracing evolutionary relationship among polyploid lymegrass species using fluorescence in situ hybridisation method

Session

Poster Session

Authors

Kesara Anamthawat-Jónsson (1)

Affiliations

1. Institute of Life and Environmental Sciences, University of Iceland

Keywords

Fluorescence microscopy, molecular cytogenetics, plant science, polyploidy

Abstract text

Leymus Hochst. (lymegrass) is a genus of about 50 polyploid perennial grass species in the wheat tribe Triticeae. Lymegrass is an ecologically important plant due to the ability to bind soil and sand with its extensive rhizome system. Some species are forage grasses. Lymegrass has its distribution over the temperate regions of the Northern Hemisphere. Six polyploid Leymus species were examined in this study: three from western North America, i.e., L. cinereus, L. innovatus and L. triticoides, in comparison with three species from Eurasia and Central Asia, i.e., L. chinensis, L. multicaulis and L. racemosus. The method of fluorescence in situ hybridization (FISH) was used to identify DNA sequences specific to different versions of the Ns genome of Leymus, with an aim to trace evolutionary relationship among these lymegrass species. Ns genome belongs to the diploid genus Psathyrostachys Nevski, the ancestor of all polyploid Leymus species. Two Ns-specific repetitive sequence families were obtained: the PshA family comprising five 384-745 bp DraI clones from Ps. huashanica (China) and the PsjD family comprising six 570-625 bp ScaI clones from Ps. juncea (Russia). The sequence analysis showed over 90% homology within family. Southern blot experiments revealed specificity of PshA to American Leymus species, but PsjD to Eurasian/Asiatic species. FISH experiments revealed physical location of PshA and PsjD sequences on chromosomes, both located on subtelometic heterochromatic regions. PshA hybridized to 22 sites on chromosomes of Ps. huashanica and the American Leymus species, whereas PsjD was localized to only 14 sites on chromosomes of Ps. juncea and the Eurasian/Asian species. The species identity was confirmed with FISH mapping of the 45S ribosomal repeats. We conclude that the American Leymus species under study are alloploid containing half of its Ns genomes deriving from Ps. huashanica, which has a very restricted distribution in China. On the other hand, Leymus species from Eurasia and Central Asia may have derived from Ps. juncea, which occurs in the same distribution range.

Acknowledgements: Snædís Björnsdóttir, Ægir Thór Thórsson and Sæmundur Sveinsson