Co-Occurrence of Long-Lasting Retrotransposon Activity and Lack of Symmetric CG Methylation in the Genome of Arabis alpina

In this workshop I will present our analysis of the 375 Mb genome of the perennial model plant A. alpina, a close relative of the annual plant Arabidopsis thaliana. We observed long-lasting as well as recent TE activity predominately driven by Gypsy long terminal repeat (LTR) retrotransposons. Their accumulation close to the centromeres extended the peri-centromeres and transformed large and formerly euchromatic clusters of genes into repeat-rich peri-centromeric regions with reduced levels of meiotic recombination. The accumulation of LTR retrotransposons in A. alpina co-occurs with unexpectedly low levels of DNA methylation. Most remarkable is the absence of symmetrical CG methylation suggesting dramatically reduced levels of DNA methylation maintenance. Phylogenetic reconstructions of the gene families with function in the DNA methylation indicated lineage-specific evolution of the methylation maintenance machinery, in contrast to conserved evolution of de novo DNA methylation between Brassicaceae species.