Fig. 5. Fj regulates N ligand expression. (A,B) Comparison of fj-lacZ (green) and Ser (red) expression in everting pupal leg. Expression is complementary in tarsal segments T2-4 (inset of T2 and T3) while expression overlaps in T1, where fj-ß-gal expression is lower in cells also expressing Ser (arrow). (C,D) Ser expression (red) in wild-type (C) and fj^d1 (D) everting pupal legs. To help identify the tarsal segments, we used a reporter gene construct, I-2.2 (green)(Bachmann and Knust, 1998), which is expressed in T1-4 in a pattern complementary to endogenous Ser. Ser expression is dramatically reduced in T2 of fj^d1 while I-2.2 expression remains. (E-H) ptc-Gal4 UAS-GFP UAS-fj mid-third instar leg discs. ptc-Gal4 drives expression of GFP (green) and fj in a stripe along the anterior side of the AP compartment boundary. (E,F) Ser (red in E and white in F) expression is induced in cells adjacent to those expressing fj (arrows). (G,H) Dl (red in G and white in H) expression is also induced in cells adjacent to fj-expressing cells (arrows). (I,J) dpp-Gal4 UAS-GFP UAS-fj mid-third instar leg discs. dpp-Gal4 drives expression of GFP (green) and fj in the anterior compartment. Ser (red in I and white in J) is induced non-autonomously in posterior cells abutting those expressing high levels of fj (arrows). Ser and Dl were visualized by antibody staining.