Orthologous Anopheline odorant receptors respond selectively to stereoisomers of the ubiquitous plant volatile linalool

Insects express chemical receptors within sensory neurons that are activated by specific cues in the environment, thereby influencing the acquisition of critical resources. A significant gap in our current understanding of insect chemical ecology is defining the molecular mechanisms that underlie sensitivity to plant-emitted volatiles. Linalool is a commonly-occurring monoterpene that has various effects on insect behavior, either acting as an attractant or a repellent, and existing in nature as one of two possible stereoisomers, (R)-(–)-linalool and (S)-(+)-linalool. In this study, we have used a cell-based functional assay to identify linalool and structurally-related compounds as ligands of Odorant receptor 29, a labellum-expressed receptor in the malaria vector mosquito, Anopheles gambiae (AgamOr29) as well as its homolog AgamOr53 in addition to orthologs found in Anopheles stephensi. The receptors were shown to be enantioselective to the ubiquitous plant volatile linalool and likely plant an important role in the nectar feeding behaviors of these mosquitoes.