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Fig. 5. A pre-processed form of Hedgehog, Hh-N, requires Dally-like for its activity. All panels show wg in situ hybridisation in late stage 11 embryos. (A-F) Ectopic expression of a pre-processed, cholesterol unmodified form of Hh, Hh-N. (A) In armGal4/UAShh-N embryos, ubiquitous Hh signalling activates wg transcription in the whole competence domain. (B) When the same experiment is repeated in a hh null background, ectopic wg expression is mostly unaffected. Endogenous wg expression is expected to disappear in absence of hh, which explains the slightly irregular pattern. (C) In armGal4/UAShh-N injected with dlp dsRNA, both ectopic and endogenous wg expression disappear (82%, n=39), showing that Hh-N requires Dlp for its activity. (D) In simGal4/UAShh-N embryos, Hh-N secretion from the midline activates wg transcription on both sides of the midline within each competence domain. (E) In simGal4/UAShh-N [hh^-] embryos, Hh-N activates wg transcription less efficiently and at short distance from the source, suggesting that Hh-N is partially dependent on endogenous Hh for its non-autonomous activity. However, in simGal4/UAShh-N embryos injected with dlp dsRNA (F), all ectopic wg transcription is wiped out (93%, n=54), showing that Hh-N requires Dlp activity for both its autonomous and non-autonomous effects. Both sets of experiments indicate that Dlp acts downstream of Hh processing.

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