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Fig. 6. Dally-like is required upstream or at the level of Patched in the Hedgehog
pathway. (A-C) Assays for the range of Hh signalling. (A) ArmGal4VP16/UASdlp
embryos ubiquitously express Dlp at high levels, but wg transcription
is activated in a single row of cells, as in wild type, showing that Dlp does
not stimulate the range of Hh signalling in embryos. (B) In contrast,
increasing the concentration of wild-type Hh in the cells that normally
secrete it (the En cells) stimulates wg transcription over two to
three cell diameters. (C) Repeating the same experiment with Hh-N leads to the
stimulation of wg transcription over three to five cell diameters.
(D-F) Epistatic relationship between patched (ptc) and dlp.
(D) In ptc homozygous null mutant embryos, Hh signalling is
constitutively activated and as a result wg transcription is
stimulated in the whole competence domain. (E) In ptc-
homozygous embryos injected for dlp dsRNA, ectopic wg
transcription is unaffected showing that Dlp is not required for the
constitutive activation of Hh signalling. (F) In sibling embryos which are
heterozygous for ptc and thus wild type for Hh signalling,
dlp RNAi leads to the disappearance of endogenous wg as
expected. ptc heterozygous and homozygous embryos were separated in
this experiment by the presence of lacZ expression in the
heterozygous embryos (signal at the midline in F).
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