Mechanisms of Volatile Odorant Detection and Corresponding Behavioral Effects in Drosophila

One of the central problems in neuroscience concerns the molecular basis of behavior. Animals generate appropriate behavioral responses to environmental stimuli, which are mediated by primary sensory neurons of different modalities including sight, hearing, touch, taste, and smell. Olfaction serves a major role in conveying important information concerning a variety of behavioral determinants such as food sources, danger, and cues from other members of the same species. Drosophila melanogaster provides a tractable model in which to study both the mechanisms of olfaction and subsequent behavioral outputs based on olfactory input. Additionally, basic knowledge pertaining to insect olfaction provides valuable insights into potential targets that may be used to influence insect vectors of diseases (e.g., mosquitoes and malaria or dengue fever), or to improve agriculture by affecting pollination by foraging insects (e.g., honeybees). My research has focused on the molecular mechanisms involved in detection of pheromones, naturally-occurring insect repellents, and food source-derived odorants by primary sensory neurons in Drosophila and the corresponding behaviors generated by these stimuli. To date, the only known volatile pheromone in Drosophila is the male-specific hydrocarbon 11-cis-vaccenyl acetate (cVA). I took a genetic approach to study the role of cVA-induced neuronal activation, and found that activation of the at1 neuronal circuit involved in cVA detection, using a dominant-active form of the odorant binding protein LUSH, is both necessary and sufficient to induce sexually dimorphic mating behavior in Drosophila. In a separate study, I identified novel olfactory sensory neurons that detect the naturally-occurring insect repellent citronellal via a mechanism involving the ion channel TRPA1. Finally, I characterized the first odorant receptor shown to be expressed in neurons of the intermediate class of olfactory sensilla, Or83c, and found that it was highly specific for a sesquiterpene found in citrus fruit peel called farnesol (FOH). Furthermore, FOH detection by Or83c instructs oviposition preference in Drosophila via ai2a sensory neurons. These studies advance general knowledge of the architecture and complexity of the Drosophila olfactory system and provide insights into the molecular basis of behaviors in insects.