Identification of srh-30 as a 2-nonanone receptor in C. elegans

C. elegans detects food, mates, and danger through a large repertoire of chemosensory receptors. The volatile odorant 2-nonanone is a well-established aversive stimulus that reliably elicits avoidance chemotaxis. However, the receptor(s) responsible for its detection have not been identified. Here, we leveraged CeNGEN single-cell expression profiles to identify candidate receptors required for sensing 2-nonanone. We narrowed the list of candidate chemoreceptor genes by selecting genes expressed in the aversive amphid neurons AWB and ASH while excluding genes expressed in other amphid sensory neurons. We tested available mutants from the C. elegans Genetics Center (CGC) and identified srh-30 as a candidate required for normal 2-nonanone avoidance. Two independent srh-30 null alleles generated using CRISPR-Cas9 confirmed that loss of srh-30 causes a partial defect in 2-nonanone sensing. srh-30 promoter-driven fluorescent reporter, mKate, localized to the distal tips of AWB sensory cilia, consistent with a direct sensory role. Finally, ectopic expression of srh-30 in the attractive AWA neuron shifted the behavioral response to 2-nonanone toward neutrality, supporting srh-30 as a sensory receptor. Together, these results identify srh-30 as a sensory receptor mediating 2-nonanone-evoked avoidance and demonstrate a transcriptome-guided strategy for mapping odor receptors.