a, Abundance of serotonin metabolites in the endo-metabolomes of tph-1(mg280), pah-1(syb3601) and pah-1(syb3596);tph-1(mg280) mutant animals relative to WT. b, Abundances of sngl#2 and sngl#4 in endo-metabolomes of tph-1(mg280) mutants fed pah-1 or cat-2 double-stranded interfering RNA (dsRNAi) bacteria, relative to RNAi control. Data in a were collected as biologically independent replicates as follows: tph-1(mg280) (n = 8 for 5-HT measurement, n = 6 for NAS and sngl#1–4 measurement), pah-1(syb3601) (n = 10 for 5-HT measurement, n = 6 for NAS and sngl#1–4 measurement), pah-1(syb3596);tph-1(mg280) (n = 4 for 5-HT measurement, n = 7 for NAS and sngl#1–4 measurement), bas-1(ad446) (n = 4). Data in b (n = 3) represent biologically independent experiments. Bars in a and b indicate mean ± s.d., P values calculated by unpaired, two-tailed t-test with Welch correction, comparing mutant and WT samples, and between mutant animals; NS, not significant. c, Inferred biosynthetic roles of PAH-1 and TPH-1 in C. elegans. d,e, GFP∷H2B∷T2A∷PAH-1 was strongly expressed in epidermal cells and in glial cells in the tail in both WT (d) and tph-1(mg280) (e) mutants. Pan-glial microRNA mir-228-fused to DsRed was crossed into both WT and tph-1(mg280) mutants, revealing pah-1 expression in a pair of glial cells (indicated by white triangles). Scale bar for all images, 15 μm. For each genotype in d and e, at least ten animals were scored at day 1 of adulthood for GFP expression under well fed conditions on at least two different days.