Extended Data Figure 5: Serotonin is downregulated by starvation and functions downstream, but not upstream, of tbh-1 transcription.

(a) tbh-1 is not required for the initial downregulation of tph-1 transcription in ADF upon L1 starvation, but is required for the formation of the persistence of this downregulation into the L3 stage. Neither initial tph-1 downregulation nor a starvation memory were apparent in NSM in a tbh-1 null mutant. In well-fed conditions, there is no significant difference between control and tbh-1 mutant animals. Center indicates median, error bars indicate quartiles. Solid lines indicate continuously-fed animals, dashed lines indicate L1-starved animals. n= number of animals, shown in each column (a, b, c). p-values shown by two-sided Wilcoxon rank-sum test (a, b, c).

(b) The ser-6 octopamine receptor is required during sexual maturation to maintain tph-1 transcription levels in ADF but not NSM under well-fed conditions, and upon starvation tph-1 transcription levels in the ser-6 mutant do not further decrease, supporting the necessity of ser-6 for proper ADF starvation response. Magenta bar indicates median, black box represents quartiles (b,c).

(c) Upregulation of tbh-1 transcription upon L1 starvation is unaffected by the addition of exogenous serotonin (5mM), suggesting that serotonin does not act upstream of tbh-1 upregulation (and subsequent octopamine production).