Fig. 4. eya, so and dpp signaling are required for regulation of 3EE-GFP. (A-C) Each set of three panels shows the same eye disc stained with anti-Dac (magenta in A-C) and anti-GFP (green in A'-C') or a merge of the two channels (A''-C''). (A-A'') Wild-type eye imaginal discs stained with GFP and Dac reveal the normal expression of endogenous Dac (A) and 3EE-GFP (A'). (B-C') so¹ (B,B') and eya² (C,C') eye imaginal discs have drastically reduced levels of Dac (B,C) and completely lack 3EE-GFP (B',C'). (D-D''') Each set of four panels shows the same eye disc stained with anti-ß-galactosidase (magenta in D), anti-Dac (green in D'), anti-GFP (green in D''), or a merge of the three channels (D'''). Posterior margin mad mutant clones, negatively marked by the lack of ß-galactosidase, block Dac (D') and GFP (D'') expression. (E,F) An eye-antennal disc from a w; UAS-ey, 3EE-GFP; dpp-Gal4 third instar larva stained with an antibody against GFP alone (E) or GFP and Dac (F). Ectopic ey expression in the antenna driven by dpp-Gal4 can strongly induce 3EE-GFP (E) and Dac (F) in the ventral antenna (arrows). (G,H) Eye-antennal discs from w; eya²; dpp-Gal4, 3EE-GFP/UAS-ey (G) and w; so¹; dpp-Gal4, 3EE-GFP/UAS-ey (H) larvae co-stained with antibodies against GFP and Dac (both panels show a merge of the two channels). Ectopic ey expression in the antenna (arrows) driven by dpp-Gal4 cannot induce 3EE-GFP expression (green in G and H) but retains the ability to induce Dac expression in the ventral antenna (magenta in G and H).