Fig. 5. Genetic removal of Su(fu) activity changes S182N Cos2 from a repressor of ptc transcription to an activator. (A,F) Expression of ptc-lacZ (red) in a wild-type (A), and Su(fu) homozygous mutant background. (B,C) MS1096 Gal4-driven S182N-GFP (green) represses normal ptc-lacZ expression at the AP border (red) in a wild-type background. (G,H) By contrast, expression of S182N-GFP (green) causes the derepression of ptc-lacZ (red) in anterior cells of a Su(fu)/+ mutant wing disc. (D,E) Expression of S182T Cos2-GFP (green) by 71B Gal4 represses normal ptc-lacZ (red) expression at the AP boundary in a wild-type background. (I,J) Expression of S182T Cos2-GFP (green) by MS1096 Gal4 represses ptc-lacZ (red) expression at the AP boundary and no ectopic ptc-lacZ expression is observed in the anterior cells of a Su(fu)/+ mutant wing disc.