Fig. 13.

Principal cell mesh knockdown in the adult Drosophila Malpighian tubule decreases transepithelial fluid and ion transport, transepithelial potential (V_t), and paracellular permeability. A and B: transepithelial basal fluid secretion (A) and K⁺ transport (B) are significantly lower in the tubules subjected to 14-day adult-onset principal cell mesh knockdown (w;tub-GAL80^ts20/UAS-mesh^RNAi;c42-GAL4/+) compared with control female fly tubules (w;tub-GAL80^ts20/+;c42-GAL4/+ and w;UAS-mesh^RNAi/+). Here, n = 33–34 tubules per genotype, one-way ANOVA P < 0.0001. ***P < 0.001, **** P < 0.0001. Adjusted P values in multiple comparisons testing are shown in Table 3. C and D: fluid and K⁺ secretion is stimulated by Drosophila kinin (DK, 1 µM) in control and mesh knockdown tubules. Here, n = 33–38 tubules per genotype/condition, two-way ANOVA P < 0.0001 for the effects of genotype, DK treatment, and interaction. ***P < 0.001, ****P < 0.0001. Adjusted P values in multiple comparisons testing are shown in Table 3. E: V_t is diminished in mesh knockdown tubules compared with control tubules (w;tub-GAL80^ts20/+;c42-GAL4/+) and is further reduced in both groups in the presence of DK. Here, n = 9–20 tubules per genotype, repeated measures two-way ANOVA P = 0.0204 for the effect of genotype, P < 0.0001 for the effect of DK, and P = 0.2686 for the interaction. *P < 0.05. Adjusted P values in multiple comparisons testing are shown in Table 4. F: Mesh knockdown tubules have reduced paracellular flux of FITC-labeled 3–5-kDa dextran (FITC-dextran). FITC-dextran flux in control and mesh knockdown tubules is not affected by DK. Here, n = 31–34 tubules per genotype, two-way ANOVA P < 0.0001 for the effect of genotype, P = 0.4122 for the effect of DK, and P = 0.8692 for the interaction. *P < 0.05, ***P < 0.001, ****P < 0.0001. Adjusted P values in multiple comparisons testing are shown in Table 5. RNAi, RNA interference; UAS, upstream activation sequence. All data are expressed as means ± SE.