Fig. 4. w does not affect fluid transport but has a direct effect on cGMP transport. (A) Fluid transport rates by wild-type (Canton S, black circles) and w¹¹¹⁸ (Bloomington stock, red squares and `cantonised' stock, red triangles). Malpighian tubules were stimulated by cGMP (100 µmol l^–1, added at 30 min, indicated by arrow). Data are expressed as mean (± s.e.m.) fluid transport rate in nl^–1 min (N=7). (B) Ratio of cGMP and cAMP transport by Canton S and w¹¹¹⁸ Malpighian tubules. Data are mean ratios ± s.e.m. (N5). (C) Ratio of cGMP (100 µmol l^–1) transport by Canton S tubules and by tubules from cantonised w¹¹¹⁸ and w^H lines. Data are mean ± s.e.m. (N5). (D) Ratio of cGMP (100 µmol l^–1) transport in three independently derived parental transgenic w::eYFP lines (4D, 5E, 8H, unshaded bars) and offspring from crosses to a GAL4 driver, c42 (c42/w::eYFP; grey bars). Data expressed as a ratio of cGMP transport ± s.e.m. (N5). cGMP transport for the c42 GAL4 driver was: 1.9±0.17 (N=7). Significance of data between progeny compared to parental controls of each line is indicated by ^**P<0.01; ^*P<0.05, Student's t-test. (E) Q-PCR of w mRNA levels in untreated (control) tubules; and in tubules treated with 100 µmol l^–1 cGMP. w expression was normalised against a cDNA standard (rp49) as previously described. Data are expressed as mean (± s.e.m.) fold-difference of w expression of cGMP-treated tubules compared to control tubules (N=4). ^***Data significantly different from control (P<0.001; Student's t-test).