Figure 4.

Ubx-VP16 overrides the repression effect of abd-A on dpp. (A–C) dpp expression in the midgut mesoderm (arrowheads) of wild-type (A), UAS-Ubx/arm-GAL4⁴ (B), and UAS-Ubx-VP16/arm-GAL4⁴ (C) embryos. PS7 is marked as a bar. Notice that Ubx does not activate dpp posterior to PS7, because of repression of dpp by Abd-A (33). Ubx-VP16 activates dpp posterior to PS7, even in abd-A⁺ embryos. dpp transcripts were visualized by in situ hybridization with a dpp antisense RNA probe. Embryos are shown at stage 13 in dorsal view.