The fruit fly, Drosophila melanogaster, has an acute sense of smell that permits it to locate sources of food with great accuracy. Fruit flies strongly prefer fermenting fruit as a food source. The overall goal of this project is to understand how their olfactory system permits these insects to recognize and discriminate the vast number of odorants in the environment, and thereby locate their preferred food source. Proteins called odorant receptors are present in the nerve cells of the antenna, and these are thought to be responsible for relaying olfactory information from the outside world into the fly's brain. Each such nerve cell, or olfactory receptor neuron, expresses a different odorant receptor, permitting it to identify odorants in the environment. Interestingly, a single odorant receptor, called Or83b, is present in all olfactory receptor neurons. As such, its role is at odds with the antenna's function to distinguish among different odorants. This proposal asks what role this unique odorant receptor plays in the olfactory system of the fly. Will flies that lack this protein be unable to respond to olfactory stimuli? Knowledge gained from these experiments may prove to be useful in mitigating the effects of deleterious insects on the environment. Pest insects locate food crops and animal hosts largely through olfactory cues. Understanding the function of Or83b in Drosophila may result in strategies to control the olfactory behavior of deleterious insects that attack agricultural crops and act as human disease vectors. The education component of this CAREER award involves a course entitled Evolutionary Biology of Brain Morphology and Function, which targets pre-graduate students who come to the Rockefeller University campus under the auspices of the University's Science Outreach Program. The course will provide students with hands-on experience in molecular neurobiology, supplemented with outside lectures, and will ask if species-specific behavioral differences have a basis in brain morphology.