Figure 3. The cGMP-gated channel subunit TAX-2 acts in the AQR, PQR, and URX neurons to regulate the aversive response to osmotic upshifts. A, The mutant animals osm-9(ky10) cultivated under the standard condition display an increased turning rate in the hyperosmotic solution of 400 mOsm that is similar to that of WT animals. n = 31 and 29 WT animals tested in 150 and 400 mOsm, respectively; n = 32 and 31 osm-9 animals tested in 150 and 400 mOsm, respectively. B, C, Two mutation alleles of tax-2, p691 and p671, are severely defective in increasing the turning rate in response to the osmotic upshift from 150 to 400 mOsm, compared with WT animals. For B, n = 24 WT animals were tested in either 150 or 400 mOsm and n = 20 and 24 p691 animals were tested in 150 and 400 mOsm, respectively; for C, n = 23 and 24 WT animals were tested in 150 and 400 mOsm, respectively, and n = 21 and 27 p671 animals were tested in 150 and 400 mOsm, respectively. D, E, Expressing the genomic DNA fragment containing the coding region and regulatory sequences of tax-2 (Ptax-2::tax-2) rescues the defects in both tax-2 alleles. For D, n = 32 and 31 WT animals tested in 150 and 400 mOsm, respectively; n = 29 and 31 transgenic animals expressing Ptax-2::tax-2 tested in 150 and 400 mOsm, respectively; and n = 28 and 26 p691 mutant sibling animals tested in 150 and 400 mOsm, respectively; for E, n = 31 and 32 WT animals were tested in 150 and 400 mOsm, respectively; n = 31 and 32 transgenic animals expressing Ptax-2::tax-2 were tested in 150 and 400 mOsm, respectively; and n = 30 p671 mutant sibling animals were tested in either 150 or 400 mOsm. F, Expressing the wild-type tax-2 cDNA in the body cavity sensory neurons AQR, PQR, URX (Pgcy-36::tax-2) rescues the defects in the tax-2(p691) mutants in generating an increased turning rate in response to the osmotic upshift from 150 to 400 mOsm. n = 24 and 22 WT animals tested in 150 and 400 mOsm, respectively, n = 22 and 24 transgenic animals expressing Pgcy-36::tax-2 tested in 150 and 400 mOsm, respectively, n = 23 and 24 p691 mutant sibling animals tested in 150 and 400 mOsm, respectively. G, Expressing cell death-promoting molecule EGL-1 in the body cavity sensory neurons AQR, PQR, and URX (Pgcy-36::egl-1) abolished the increased turning rate in response to the osmotic upshift from 200 to 400 mOsm. n = 36 and 44 WT animals were tested in 200 and 400 mOsm, respectively; n = 40 and 44 transgenic animals expressing Pgcy-36::eg-1 were tested in 200 and 400 mOsm, respectively. H, The heat map of the calcium signals in the URX neuron in individual animals that were exposed to 150 mOsm and switched to 400 mOsm and in individual animals that were exposed to 150 mOsm and switched to 150 mOsm. The calcium signal was presented as the percentage change in GCaMP6 signal using the average GCaMP6 signal in the first 60 s as the baseline [(F − Fbase)/Fbase * 100%; see Materials and Methods]. I, The average change in the GCaMP6 signal in URX is significantly higher when animals are switched from 150 to 400 mOsm (n = 15) than when animals are switched from 150 to 150 mOsm (n = 13). Box plot shows the first and third quartile, median, and the maximum and minimum. The Student’s t test was used for comparison. For A–C and G, significant interaction between genotype (wild-type vs mutant animals) and osmolarity is tested with two-way ANOVA; for D–F, significant interaction between genotype (transgenic vs nontransgenic siblings) and osmolarity is tested with two-way ANOVA. For all, animals are cultivated under the standard NGM plates with an osmotic condition of 150 mOsm. ***p < 0.001, **p < 0.01, *p < 0.05. n.s., Not significant. Values are reported as the mean ± SEM. WT, wild type.