Natural Variation in C. elegans 1-Octanol Olfactory Avoidance Behavior

The detection of chemical stimuli is a fundamental driver of animal behavior. Odorants and tastants provide essential information about not just food availability and quality, but also about environmental conditions and safety. However, much of what we know about how animals respond to their surroundings comes from the study of a limited number of laboratory-adapted strains of model organisms. In the case of C. elegans, chemosensory research has focused almost exclusively on the N2 strain first isolated in Bristol, England in 1951 and which has been deemed the wild-type reference for studies of the species since that time. A collection of hundreds of wild C. elegans strains gathered from around the globe and whole-genome sequence data are now available through the Caenorhabditis Natural Diversity Resource. Using these resources, we assessed natural variation in behavioral sensitivity to the aversive odorant 1-octanol. We found that the wild strains either responded similarly to N2 or were less sensitive. No hypersensitive strains were seen among those tested. Using genome-wide association studies we identified a single QTL on the right arm of chromosome II correlated with diminished behavioral avoidance of 1-octanol and confirmed its role using near-isogenic lines. Building upon our recent report of wild strain taste responses, this study is only the second of this scale to investigate how natural genetic variation shapes C. elegans chemosensory behavior, focusing for the first time on olfaction.