Fig. 5. Bar autoregulates its expression. (A-C) Bar expression in the basal undifferentiated cells is maintained after expression of its two activators, Hh and Ato, has ceased. A hh¹ mutant eye disc stained with antibodies for Elav (red), BarH1 (green) and Ato (blue) is shown at the apical photoreceptor level (A) and the basal undifferentiated cell level (B). Ato expression is strongly downregulated but Bar expression is quite normal in hh¹ mutant eye disc. In A, an arrow marks the arrested furrow. (C) A longitudinal section of hh¹ mutant eye disc. (D) A longitudinal section of wild-type eye disc. (E-L) Bar positively autoregulates its transcription. Misexpression of BarH1 by dpp-GAL4 in the background of BarH2^P058-lacZ ectopically induces lacZ expression (H,L; arrows) in the region of BarH1 misexpression shown by ectopic BarH1 protein in the ventral region of eye disc (E-H) and along the anteroposterior (AP) border of leg disc (I-L). The ventral region of eye disc marked by a rectangle in E is magnified in F-H. (I) The wild-type pattern of Bar expression (red) in a ring domain and the dpp driver pattern by GFP reporter expression (green) along the AP axis.