Mealybug Chromosome Cycle as a Paradigm of Epigenetics

Figure 5

Pattern of epigenetic marks in P. citri cleavage embryos. Localization of C1A9 (anti-HP1) and anti-K9H3me3 antibodies to nuclei in midcleavage embryos (128–256-nuclei embryos) undergoing facultative heterochromatinization. (a) Whole embryo: the wave of facultative heterochromatinization is spreading from the bottom left corner toward the top right corner. Boxed area (B) shows nuclei that have completed heterochromatinization and contain DAPI-positive chromocenters (see magnified image in b), whereas boxed area (C) shows nuclei still undergoing heterochromatinization, many of which have no overt DAPI-positive chromocenters (arrows in c). The nuclei in b are labeled with the anti-HP1 antibody (b′) and the anti-K9H3me3 antiserum (b′′). The merged image in b′′′shows colocalization of DAPI-positive chromocenter, HP1 and K9H3me3 staining. The DAPI-stained nuclei in c were stained with anti-HP1 antibody (c′) and the anti-K9H3me3 antiserum (c′′). Although the pattern of K9H3me3 staining is more spread out in these nuclei compared with those that have completed heterochromatinization (compare c′′to b′′) the merged image in c′′′shows that the K9H3me3 pattern largely colocalizes with HP1 staining. C1A9 antibody recognizes the P. citri HP1-like, PCHET2. Bars, 10 μm. Reprinted from Bongiorni et al. 2007 [40].