Molecular Organization of 5S Ribosomal DNA and Taxonomic Status of Avenella flexuosa (L.) Drejer (Poaceae)

The wavy hair-grass, Avenella flexuosa (L.) Drejer (also known as Deschampsia flexuosa (L.) Trin. or Lerchenfeldia flexuosa (L.) Schur), is a species of perennial herbaceous plant of the Poaceae family that is widespread in Eurasia, Africa, North and South America. Whether this species belongs to the Deschampsia genus has long been an open question. Taking into account that the 5S rDNA comparison is a convenient tool in the molecular taxonomy of plants, we cloned and sequenced this region of the A. flexuosa genome and evaluated the genetic distances between this species and other species of the Poeae tribe. It has been found that at least two structural classes of 5S rDNA repeats are present in the A. flexuosa genome. The spacer regions in the 5S rDNA of A. flexuosa and D. antarctica have a low level of similarity that does not exceed the level of similarity with representatives of several other genera of the Poeae tribe. The 5S rDNA clones of A. flexuosa and D. antarctica form two distinct clades on the phyllodendogram. Taking together, our results support the idea that A. flexuosa belongs to a separate genus Avenella.