Fig. 3.

tsl overexpression in either the BCs or the CCs is sufficient to trigger Tor receptor activation at the anterior end of the embryo. (A) Cuticle preparation of a WT embryo. (A′) Detail of the WT head skeleton; the dorsal bridge (DBr) and the dorsal arm (DA) are anterior terminal structures. (B) Anterior and posterior terminal structures do not develop in tsl⁶⁰⁴ homozygous mutant embryos. (B′) The dorsal bridge does not form and the dorsal arm is reduced. (D, F, and H) Overexpression of tsl with the slboGAL4, tsl(G)GAL4 and tsl(F)GAL4 drivers (see pattern of expression in C, E, and G, respectively) rescue the anterior terminal structures of tsl⁶⁰⁴ mutant embryos; there is also rescue of the posterior terminal structures with the slboGAL4 and tsl(G)GAL4 drivers, which is variable with the slboGAL4 driver. (D′, F′, and H′) Details to show that dorsal bridges are formed at the anterior end using the three drivers.