Fig. 8.

Developmental principal cell mesh knockdown in the Drosophila Malpighian tubule abolishes transepithelial fluid and K⁺ transport and response to drosokinin and causes a bloated abdomen phenotype. A and B: main segment fluid secretion (A) and K⁺ transport (B) is detected in 1-day-old adult control female fly tubules (w;c42-GAL4/+ and w;UAS-mesh^RNAi/+), but not the developmental principal cell mesh knockdown tubules (w;UAS-mesh^RNAi/+;c42-GAL4/+). Flies were reared at 28°C. Here, n = 22–30 tubules per genotype, one-way ANOVA P < 0.0001. C and D: Drosophila kinin (DK, 1 µM) treatment resulted in increased transepithelial fluid secretion and K⁺ flux in control tubules but had no effect on mesh knockdown tubules. Flies were reared at 18°C. Here, n = 33–34 control tubules per condition (100% of analyzed tubules secreting), and n = 5–7 mesh knockdown tubules per condition (~18% of analyzed tubules secreting); two-way ANOVA P < 0.0001 for the effects of genotype and DK and P = 0.0055 (C) and 0.0028 (D) for the interaction. ****P < 0.0001. E and F: mesh knockdown flies have distended abdomens with significantly larger abdominal volume. Flies were reared at 18°C. Here, n = 21 flies per genotype, one-way ANOVA P < 0.0001. Data are expressed as means ± SE; ****P < 0.0001. RNAi, RNA interference; UAS, upstream activation sequence. Adjusted P values for all multiple comparisons testing are shown in Table 1.