Mealybug Chromosome Cycle as a Paradigm of Epigenetics

Figure 6

Localization of K20H4me3 in P. citri nuclei undergoing either facultative heterochromatinization or developmental de-heterochromatinization. (a) DAPI-stained nuclei from a midcleavage embryo (128–256-nuclei embryo) that underwent facultative heterochromatinization. A clear DAPI-stained chromocenter can be seen in each nucleus. The same nuclei were labeled with C1A9 (anti-HP1) antibody (a′) and with the anti-K20H4me3 antiserum (a′′); the merged image in a′′′ shows coincidence of DAPI-positive chromocenters with HP1 and K20H4me3 staining. The nuclei in b are from another area of the same embryo that has yet to complete heterochromatinization and several have no overt DAPI-positive chromocenters. The DAPI-stained nuclei in b were simultaneously stained by anti-HP1 antibody (b′) and by the anti-K20H4me3 antiserum (b′′). Whereas the K20H4me3 staining is more dispersed in these nuclei compared with those that have completed heterochromatinization (compare b′′ to a′′), the merged image (b′′′) shows that the K20H4me3 pattern largely colocalizes with HP1 staining. (c) DAPI-stained nuclei from cells of adult tissues that undergo developmental reversal of heterochromatinization. HP1 staining is dispersed and has a grainy appearance over the nuclei (c′) that, instead, lack any K20H4me3 staining which is rather dispersed over the cytoplasm (c′′). (c′′′) Merged image. Bars, 10 μm. Reprinted from Bongiorni et al. 2007 [40].