Olfaction and odor discrimination are mediated by the C-elegans guanylyl cyclase ODR-1

Animals in complex environments must discriminate between salient and uninf ormative sensory cues. Caenorhabditis elegans uses one pair of olfactory ne urons called AWC to sense many different odorants, yet the animal can disti nguish each odorant from the others in discrimination assays. We demonstrat e that the transmembrane guanylyl cyclase ODR-1 is essential for responses to all AWC-sensed odorants. ODR-1 appears to be a shared signaling componen t downstream of odorant receptors. Overexpression of ODR-1 protein indicate s that ODR-1 can influence odor discrimination and adaptation as well as ol faction. Adaptation to one odorant, butanone, is disrupted by ODR-1 overexp ression. Olfactory discrimination is also disrupted by ODR-1 overexpression , probably by overproduction of the shared second messenger cGMP. We propos e that AWC odorant signaling pathways are insulated to permit odor discrimi nation.