(A–B) tph-1 expression in ADF, but not in NSM, restores feeding rate in the tph-1 null mutant. The rescue effect is suppressed by loss of ser-7, but not by loss of mod-5. No difference was found in feeding rates between the tph-1 single null mutant, the ser-7 single null mutant and the tph-1; ser-7 double null mutant. The average values of the feeding rates presented in (A) are 266.1 ± 3.0, 207.7 ± 1.9, 206.6 ± 4.2, 277.2 ± 6.0, 261.1 ± 5.3, 216.4 ± 4.0, 267.3 ± 3.1, 217.5 ± 2.8, 204.1 ± 3.0 and 216.9 ± 1.8 in order. (C–D) ADF-minus animals, but not NSM-minus animals, feed significantly less in response to familiar food. (E) Expression of ser-7 cDNA driven either by the flp-2 promoter or by the flp-21 promoter (MC, M4, and other neurons) but not by the ser-7b promoter (M4 only) fully restored the feeding rate in the ser-7 null mutant in response to serotonin. The rescue effect was suppressed by blocking cholinergic transmission from MC to the pharyngeal muscles. #Pharyngeal pumping rate was lower in the eat-2; ser-7 double null mutant than the eat-2 single null mutant (p<0.001) and the ser-7 single null mutant (p=0.002). The difference suggests that acetylcholine marginally activates pumping in an EAT-2-independent manner and that there is residual acetylcholine release in absence of SER-7 in response to serotonin. No difference in feeding rates was found between the eat-2; ser-7 mutant expressing pflp-21::gfp and the mutant expressing pflp-21::ser-7 cDNA. The average values of the feeding rates presented in (E) are 73.6 ± 3.3, 12.2 ± 1.8, 39.3 ± 7.1, 51.2 ± 8.9, 117.8 ± 13.7, 107.7 ± 10.4, 132.6 ± 10.6, 16.9 ± 3.1, 2.9 ± 1.0, 8.3 ± 4.1 and 15.6 ± 1.4 in order. (F) Expression of ser-7 cDNA driven either by the flp-2 promoter or by the flp-21 promoter fully restored the feeding rate in the ser-7 null mutant in response to familiar food. Expression of ser-7 cDNA in M4 (and occasionally in M2) driven by the ser-7b promoter also increased the feeding rate, but the effect was relatively small. The average values of the feeding rates presented in (F) are 189.7 ± 2.6, 194.9 ± 3.4, 212.0 ± 5.1, 245.1 ± 4.7, 240.7 ± 4.6 and 253.6 ± 2.5 in order. Data shown as mean ± SEM, n.s., not significant (p≥0.05), *p<0.05, ***p<0.001; for (A–B) and (E–F), one-way ANOVA, post hoc Tukey test, for (C–D), unpaired t-test and Mann–Whitney U test (two-tailed). The number of animals tested (n ≥ 3 independent assays per each group) is shown on each bar. ‘0’ and ‘wt’ in this figure indicate absence of transgene and wild type, respectively.

DOI: http://dx.doi.org/10.7554/eLife.00329.010