Figure 3.

OUbx regulates target genes in the Drosophila wing and in the embryonic midgut. (A) Wild-type expression of SRF in the pouch region of the wing imaginal disc. (B and C) Expression of SRF (red) and Ubx (green) in the wing pouch where ectopic expression of DUbx1a (B) or OUbx (C) is driven by MS1096-Gal4. SRF expression is repressed, particularly in the dorsal compartment where ectopic DUbx1a (B) or OUbx (C) expression is high (arrowheads). Insets show the single channel of SRF expression in the center of the wing pouch, in the region of the arrowhead in the larger panel. In the lower right corner of B and C the edge of another imaginal disc from the third thoracic segment of the same animal is visible, indicating that the levels of ectopic protein expression in B and C are comparable to each other and to endogenous DUbx protein expression. (D) Wild-type expression of the dpp674 embryonic midgut enhancer in PS7 of the visceral mesoderm in a stage-13 embryo. dpp674 also drives expression in the gastric caeca at the anterior of the midgut independent of Ubx regulation. The gap between these expression domains is indicated by an arrow. Expression of DUbx1a (E) or OUbx (F) driven by 24B-Gal4 causes ectopic expression of dpp674 anterior to PS7 (arrow). The OUbx phenotype is typically less strong than DUbx1a, though the ectopic activation of dpp674 generated by either Ubx protein is often patchy.