Expression of the siss-1 gene in C. elegans.

C. elegans SISS-1 is an Epidermal Growth Factor (EGF) family ligand that signals from damaged cells to sleep-promoting neurons during s tress- i nduced s leep (SIS). Damage to a range of tissues can trigger SIS, and we reasoned that siss-1 should be widely expressed. Here we investigate siss-1 expression using both endogenous and transgenic fluorescent reporters. Our endogenous reporter reveals siss-1 expression in the pharynx, gut, rectal gland, vulval muscles, and a subset of neurons. Our transgenic reporters reveal expression in additional cell types including the distal tip cell of the migrating gonad and vulF cells of the developing vulva. This expression is specific relative to our expectation and suggests that not all tissues are capable of signaling to sleep neurons.