Figure 8

Cellular blastoderm and heterochromatin formation mark a key decision point for epigenetic marks. H3K27me3 levels in (A) heterochromatic regions and (B) gene promoters (hb, nullo, bnk, Ubx, h) during early development in wild-type and embryos from Su(var)2-5 ⁰⁵ /CyO parents. Key to bar colors is in (B). (B) hb, nullo, bnk, Ubx, and h promoters scored during the time windows on the X axis. The signal at all the euchromatic gene promoters shows a switch between the 2–4 and 3–5 h windows going from less than, to greater than wild-type in the embryos from Su(var)2-5 ⁰⁵ /CyO parents. The heterochromatic regions are a little more variable with TART and 1360 showing the switch a little earlier (2–4 h). Note the 1–3 h data is the same as in Figures 2A and 3, regraphed to show the changes over time. (C) Transcript levels of heterochromatic regions in 2–4 and 3–5 h embryos from Su(var)2-5 ⁰⁵ /CyO parents relative to wild-type (set to one, broken line across). All but F-element show a decrease in the 3–5 window. F-element shows the decrease later in the 5–7 h window. Difference between time windows is significant in all cases. The RNA analysis takes into account the copy number of the repetitive elements (normalized to a single copy gene in both genotypes) as it has been previously demonstrated that loss of HP1a can alter the copy numbers of HeT-A and TART at telomeres [62,63]. Asterisks show differences significant from wild-type, *P value <0.05, **P value <0.005, ***P value <0.0005, ****P value <0.0001. Number symbols (#) in (C) are for the same P values. Error bars represent ± SEM. NI, non-immune; hb, hunchback; bnk, bottleneck; Ubx, Ultrabithorax; h, hairy.