Figure 7.

A model for a two-layer transcriptional activation of tph-1 expression in the ADF neurons. a, Under optimal growth conditions, TRPV signaling is required to turn on tph-1 expression, whereas IFT/Hh-like signaling represses tph-1 expression via an independent mechanism. b, In dauers and heat-shock survivors, IFT/Hh-like signaling is perturbed, which alters the cilium architecture of the ADF neurons, resulting in derepression of tph-1 expression. As the TRPV channel continues at work, tph-1 expression is upregulated to catalyze more 5-HT biosynthesis.