Fig. 4. The nkd-WRE reporters are positively regulated by Wg signaling.

(A) Stage 14 embryo containing the nkd-IntE reporter stained for LacZ (red). Several expression domains consistent with positive regulation by Wg signaling are evident, including regions of the head (h), proventriculus (pv), visceral mesoderm (vm) and hindgut (hg). (B) IntE pattern in a wg mutant embryo. Most of the pattern is absent, except for the dorsal domain indicated by white arrowheads. (C) Stage 14 embryo with a smaller (255 bp) IntE reporter shows staining in a subset of the larger fragment. (D) IntE (255 bp) staining is abolished when the three TCF binding sites indicated in Fig. 2B are mutated. (E–L) The nkd-UpE1 and UpE2 WREs require Wg signaling in late third instar wing imaginal discs. (F, I, L) Expression of a dominant negative form of TCF (TCF^DN) in the posterior compartment of the wing pouch (via En-Gal4; marked with arrowheads). TCF^DN inhibits expression of UpE1 (F), UpE2 (I) and the Wg readout Sens (L). The broader expression of lacZ in the anterior compartment of UpE1 discs (F) is likely due to distortion of disc morphology caused by TCF^DN expression. The slightly elevated expression of lacZ in the posterior compartment of UpE2 discs (H) is not always observed (see Fig. 3M). (G) Expression of a stable form of Arm (Arm^S10) along the anterior/posterior boundary of the wing pouch (via Dpp-Gal4; white arrows) results in marked expansion of nkd-UpE1 expression. The decrease in lacZ expression at the dorsal/ventral boundary is likely due to distortion of patterning in the Dpp/Arm^S10 discs. (J) Mutation of the two TCF binding sites in UpE2 (the same ones indicated in Fig. 2A) abolishes reporter expression in the pouch and hinge regions of the wing imaginal discs. For the TCF mutant constructs, three independent lines were examined with identical results as those shown.