Fig. 2. Ubx controls the expression of Dpp targets. (A-B'') omb-lacZ (in red) and En (in green) expression in wing (A-A'') and haltere (B-B'') imaginal discs. A and P stand for anterior and posterior compartments, respectively. In bx³/TM2 (C-C'') and pbx/TM2 (D-D'') haltere discs the omb expression extends significantly in the anterior (C) and posterior (D) compartments, respectively. Arrowheads in A-D mark the A/P boundary. (E-F'') Ubx mutant clones, marked by the absence of GFP expression (in green) and showing omb-lacZ expression (in red). Note in E' the extended expression of omb in Ubx^- cells (arrow). In F-F'' there are three types of clones: a clone far from the A/P boundary does not activate omb (asterisk in F); clones closer to this boundary show extended omb expression (arrowhead in F and F', posterior clone), and another clone (arrow in F, anterior clone) activates omb also outside the clone (the arrow in F' points to non-cell-autonomous omb expression). Merged images in E'' and F''.