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Evolution, Diversity and Phylogeny of 5S rDNA Unit Arrays in Diploid and Polyploid members of the Tribe Anemoninae (Ranunculaceae)

The tribe Anemoninae is composed of ~200 species divided into two subgenera according to the basic chromosome number: Anemone x=8 and Anemonidium x=7. We have performed extensive study of evolution, diversity and phylogeny of 5S rDNA in diploid and polyploid species of the tribe Anemoninae. Our results show that diversification of Anemoninae into two subgenera was accompanied with major changes in 5S rDNA that led to different 5S unit array length, GC content and 5S rDNA sequence structure. Existence of 5S shorter than typical unit size variants in Anemone and longer than typical in Hepatica indicates that 5S rDNA has undergone two rounds of evolution: contraction and extension. The presence of MITE‐like transposable elements in Hepatica suggests that amplification of 5S rDNA is transposonmediated. 5S rDNA of the Anemoninae tribe was shaped by week homogenization fo rces as indicated by high intra‐individual nucleotide diversity, presence of 5S unit array length variants and pseudogenes. Phylogenetic study supports the hypothesis that A. parviflora could be the donor of the D subgenome to allopolyploids A. multifida and A. baldensis. Both allopolyploids undergone diploidization process including loss of 5S rDNA from the D subgenome and replacement with those of the B subgenome. Phylogeny of Hepatica confirmed allopolyploid origin of H. transsilvanica and H. yamatutai and suggests that H. nobilis and H. insularis could be considered as their putative parental species.

5S rDNA ; Anemone ; Pulsatilla ; Hepatica ; allopolyploidy ; concerted evolution

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