Fig. 4

Sequence composition of H3K9me2-heterochromatin (H3K9me2 ChIP-Seq). Proportional read counts assigned to individual sequence clusters are divided into main repeat groups (a), and subsequently into clades and families (b and c). The repeat proportions reflect their abundances within sugar beet H3K9me2-heterochromatin. Read counts are normalized to the overall read amount introduced into the clustering approach. a H3K9me2-heterochromatin displays heterogeneity in repeat composition. Satellite DNA is the most abundant repeat and is followed by LTR retrotransposons (Ty3-gypsy as well as Ty1-copia retrotransposons). b The family pEV is the prevalent satellite found in H3K9me2-heterochromatin. Regarding the abundances, the minisatellite BvSat04 and the satellites pHC, and Niobe contribute only partially to H3K9me2-heterochromatin sequences. c At least four clades of Ty3-gypsy retrotransposons are associated with H3K9me2-heterochromatin. 2 % are uncharacterized repeats and represent either putative unknown Ty3-gypsy sequences or truncated and/or recombined repeats in H3K9me2-heterochromatin. d The Cotzilla family predominantly contributes to the composition of H3K9me2-heterochromatin in Ty1-copia retrotransposons, while 1 % of the Ty1-copia sequences have not been characterized to date. e En/Spm is the prevailing DNA transposon superfamily followed by Mutator elements