Wnt pathway requirement for gland specification.

(A-F) st11 gland primordia double labelled with sna-rg-GFP in green, and in red the wg expressing cells with a wgen11 reporter line (A-B) or the vvl expressing cells with a vvl1+2-mCherry reporter line (C-F). (A) Control sna-rg-GFP wgen11-lacZ/+ embryo. sna-rg labels specifically the CA and the PG cells invaginating at the anterior end of the maxillary and labial segments respectively. (B) In wgen11 homozygous mutants, ectopic patches of sna-rg expression appear on the wingless expressing cells (arrows) in the maxilla and labium at the same dorso-ventral positions as the endogenous ones. (C) Wg ectopic expression driven in the maxillary and labial segments with spalt-Gal4 results in the downregulation of sna-rg expression (asterisks). Downregulation of vvl1+2 cephalic expression is also observed. (D) Ectopic expression of activated Armadillo results in sna-rg downregulation (asterisks). (E) pan2(dTCF) null mutants present normal sna-rg expression and Engrailed (blue) stripe expression is maintained. (F) wgCX4 pan2 double mutant embryos do not present ectopic endocrine primordia. Embryo in panel F is also stained with anti-Wg to recognise the homozygous wg mutants. Scale bar 50 μm.