Fig. 6

Simplified model of histone modifications/substitutions in relationship with major repeats in CenH3-chromatin and H3K9me2-heterochromatin. A typical metacentric sugar beet chromosome composed of two chromatids is illustrated. a H3K9me2 is found in small heterochromatic sites in genic regions, in vicinity to transposons and putatively with retrotransposons, in large clusters in intercalary heterochromatin (b) and in small proportions in CenH3 chromatin (d). The underlying sequence is composed of several repeats, but the satellite pEV and the Ty1-copia retrotransposon Cotzilla predominate the sequence composition. H3K9me2 interacts with Beetle4 and occasionally with Beetle7 in pericentromeric regions (c). Active centromeres are defined by CenH3, which preferentially binds to the centromeric satellite pBV and the Ty3-gypsy retrotransposon Beetle7. Beetle4 is found in centromeric and presumably also in pericentromeric heterochromatin, in association with both, H3K9me2 and CenH3. Note, that this figure is not drawn to scale. Plastid DNA is not incorporated, due to various integration sites, which need to be further confirmed and analyzed in subsequent studies