Odorant Responses and Courtship Behaviors Influenced by at4 Neurons in Drosophila

In insects, pheromones function as triggers to elicit complex behavior programs, such as courtship and mating. In most species, the neurons tuned to pheromones are localized in a specific subset of olfactory sensilla located on the antenna called trichoid sensilla. In Drosophila there are two classes of trichoid sensilla, at1 sensilla that contain the dendrites of a single neuron that is specifically tuned to the male-specific pheromone 11-cis vaccenyl acetate (cVA), and at4 sensilla that contain three neurons with relatively poorly defined chemical specificity and function. Using a combination of odorant receptor mutant analysis, single sensillum electrophysiology and optogenetics, I have examined the chemical tuning and behavioral consequences of the three at4 olfactory neuron classes. My results indicate that one class, Or65abc neurons, previously reported to be cVA sensors, are unresponsive to cVA pheromone. Or65abc neurons inhibit courtship behaviors. The other two neuron classes, Or88a and Or47b neurons, are sensitive to a diverse array of fly and non-fly odors. Activation of these neurons has little direct impact on courtship behaviors.