Fig. 1. dRheb allele allowing GAL4-driven ectopic expression. dRheb^AV4 is a P-element (P{y⁺,5XUAS}) insertion at position +85 within the 5' UTR of dRheb (A; exons are shown as boxes, with open reading frames shaded, whereas introns are shown as lines). When the hindgut-specific driver, bynGAL4,UASGFP, is combined with dRheb^AV4, the level of dRheb mRNA in the embryonic hindgut (detected by in situ hybridization) is increased (C) and the hindgut (expressing GFP) of the first instar larva is enlarged (D) relative to that of the wild type (B); B and D are at the same magnification. Anterior extent of hindgut is indicated by arrows (B,D); hindgut overexpressing dRheb is indicated by arrowhead (C).