Maximum intensity projections of approximately stage 16 Drosophila embryos, oriented anterior left. Scale bar = 50 μm. (A) An embryo in which the expression pattern of wg-Gal4 is determined using a UAS-CD8-GFP reporter (marking cell membranes) and staining with anti-GFP. Embryo is co-stained with anti-Cut to allow visualisation of tubules. Asterisk marks expression in presumptive midgut. Right panel shows enlargement of area marked with square. B-D show embryos stained with anti-Cut and anti-Odd, with lower panels showing enlargements of boxed areas, to highlight the region where the proximal tubule of the anterior tubule pair meets the gut. Arrowheads show the distal extent of the Odd expressing tubule domain. (B) Control embryo (wg-Gal4). (C) An embryo in which wg-Gal4 is used to drive expression of UAS-wg, in a wild-type wg background. (D) An embryo in which wg-Gal4 is used to drive expression of UAS-Nrt-wg in a wild-type wg background. In this context Odd is expressed in the gut beyond both sides of the junction with the Malpighian tubules (†) that is in both the midgut and hindgut. Arrow marks patch of cells in tubule expressing Odd. (E) Graph showing mean length of Odd expressing region along tubule in control embryos (UAS-wg), and embryos in with wg-Gal4 is driving the expression of UAS-wg or UAS-Nrt-wg. Error bars represent SEM. One-way ANOVA indicated a significant statistical difference between the three genotypes (p=0.04*). Control n = 14, wg-Gal4 >UAS wg n = 20, p=0.052 (Mann-Whitney, compared to control), wg-Gal4 >UAS Nrt-wg n = 25, p=0.012* (Mann-Whitney, compared to control) and p=0.35 (Mann-Whitney, compared to wg-Gal4 >UAS wg.