Natural variation of H3K27me3 distribution between two Arabidopsis accessions and its association with flanking transposable elements

Background Histone H3 lysine 27 tri-methylation and lysine 9 di-methylation are independent repressive chromatin modifications in Arabidopsis thaliana. H3K27me3 is established and maintained by Polycomb repressive complexes whereas H3K9me2 is catalyzed by SUVH histone methyltransferases. Both modifications can spread to flanking regions after initialization and were shown to be mutually exclusive in Arabidopsis.