Fig. 1. hh functions synergistically with ey to induce Eya expression and photoreceptor differentiation. (A-F) All panels show wing discs (anterior towards the left and dorsal upwards) with different combinations of UAStransgenes driven by the 30A-GAL4 driver. The expansion of the wing disc in all panels is a result of overexpression of either dpp or hh, and reflects the capacity of these genes to induce growth and proliferation of imaginal disc cells. (A,D) ey and dpp co-expression in a ring around the wing pouch induces Eya expression (A) and photoreceptor differentiation, but only in the posterior compartment. Endogenous Eya expression in the wing disc appears as vertical stripes of staining in the anterior and posterior compartment (arrowheads in A). (B,E) When ey and hh are co-expressed, Eya is expressed (B) and photoreceptors differentiate, but only in the anterior compartment. (C,F) Overexpression of ey, dpp and hh together induces Eya expression (C) and photoreceptors in both compartments of the disc pouch. (D-F) Photoreceptor differentiation is visualized by an antibody to the pan-neuronal protein Elav.