Fig. 1. so10-lacZ activity in different mutant backgrounds. (A-I) Eye discs of third instar larvae expressing so10-lacZ. (A) Expression in a wild-type eye disc. Arrowhead indicates the ocellus region where no expression is detected. Dorsal is top and posterior is left. (B-J) Expression in an ey², ey^J5.71, so¹, eya¹, spapol and toy^G7.39 mutant background, as indicated. G and H, I and upper box in I show a pair of the eye discs from a single larva of toy^G7.39. L indicates left and R indicates right eye disc. (J) Leg disc where UAS-toy is ectopically expressed with dpp^blink-Gal4 in an ey² mutant background. lacZ staining (arrow) shows that toy is able to activate this enhancer element in the absence of endogenous ey.