Fig. 4. Ectopic expression of DMyb promotes S phase in the ZNC of larval wing discs. Views of the dorsoventral boundaries of wing discs that were double-stained with DAPI to visualize nuclei (left panels) and for DNA synthesis by BrdU incorporation (right panels). In wild-type control discs, en-Gal4/+, BrdU incorporation was not detected in the zone of non-proliferating cells (ZNC), which is composed of cells at the dorsoventral boundary (A). However, when en-Gal4 was used to drive expression of either UAS-DMyb (B) or UAS-DMyb (C) in the posterior compartment, BrdU incorporation could be detected in the posterior ZNC (indicated by arrows); and when sd-Gal4 was used to drive expression of UAS-DMyb throughout the wing pouch, no ZNC could be detected (D). Scale bar: 0.05 mm.