Fig. 9. Proposed regulatory mechanism that controls the expression of ara/caup in the prospective notum. Regulation of the activity of Iro-RE² (A) and Iro-RE¹ (B) by the EGFR and Dpp pathways is shown (green arrows, positive regulatory interactions; red T-shaped bars, negative regulatory interactions). Downstream effectors of the pathways are indicated. (C) Addition of the actions of both REs largely explains the expression of ara/caup in the prospective notum region of the third instar wing disc. Dpp expression was monitored with dpp-Gal4, UAS-GFP (A,B) and dpp-lacZ (C).