Fig. 5. pygo is required for Wg signaling in imaginal discs. (A) Micrograph of an adult wing with a pygo¹⁰ clone, showing a loss of wing margin and the accompanying bristles. Note that in place of the slender bristles (arrowhead) normally found adjacent to the stout bristles, the tissue next to the clone has ectopic stout bristles (arrows). This is characteristic of a clone that lacks Wg signaling (Rulifson et al., 1996). (B-E) Confocal images of wing imaginal discs stained for Wg (B), Sens (C) and Dll (D,E). Clones of pygo¹⁰ (marked by the absence of Arm-lacZ; not shown, clonal boundaries shown by the white lines). The normal domain of Wg expression is not affected, but Wg expression is derepressed in the adjoining area inside the pygo clone (B). Sens is missing in the pygo clone (C) and Dll is either completely absent (D), severely reduced (not shown) or modestly affected (E). (F,I) Micrographs of male mesothoracic legs of wild type (F) or a pygo^EP homozygote (I). The arrows indicate the position of the sex comb, a row of bristles found on the ventral side of the leg, which is missing in the pygo mutant (I). (G,H) Micrographs of third instar leg imaginal discs stained for dpp-lacZ in wild type (G) and pygo^EP mutants (H). The dorsal marker dpp-lacZ is derepressed on the ventral side of the pygo mutants.