Fig. 4. Dally-like is required for Hedgehog signalling. (A-C,E,F) wg transcription revealed by in situ hybridisation in wild type (A) and in embryos ectopically expressing hh (B,C,E,F). (B) In armGal4/UAShh embryos, hh is expressed in every epidermal cells. In response to Hh signalling, wg transcription is activated in half a segment, which corresponds to its competence domain. (C) In embryos of the same genotype injected with dlp dsRNA, ectopic and endogenous expression of wg disappears completely (72%, n=47), showing that dlp is required for Hh signalling. (D) In situ hybridisation against lacZ in simGal4/UASnuclacZ embryos showing that simGal4 drives expression in the ventral midline. (E) In simGal4/UAShh embryos, hh is expressed in the ventral midline. In response, wg transcription is activated over a few cell diameters on either side of the midline, in each segmental domain of competence. (F) In simGal4/UAShh embryos injected with dlp dsRNA, both ectopic and endogenous wg expression are gone (97%, n=29), confirming the requirement of dlp for Hh signalling (F). All embryos shown are late stage 11.