The insect chemosensory system has many parallels with vertebrate chemosensory systems, but is numerically simpler. The potent molecular genetic tools available in Drosophila combined with simple chemosensory behavior assays and electrophysiological analysis allow us to determine the in vivo biological function of individual components of the chemosensory system. Ultimately these results will provide insights into underlying principles of chemosensory information processing that are likely to be shared with vertebrates. We propose the following specific aims:
Specific Aim 1. Elucidate the perireceptor events and molecular components underlying sensitivity to the male pheromone, 11-cis vaccenvl acetate. In the last funding cycle we discovered the odorant binding protein LUSH is required for pheromone sensitivity in a small subset of chemosensory neurons. Remarkably, LUSH appears to function as a direct activator of olfactory neurons. We will determine whether LUSH binds directly to 11-cis vaccenyl acetate, and identify the neuronal receptor that is activated by LUSH using a targeted RNAi approach and a genetic approach. We will establish exactly how the pheromone, LUSH and the olfactory neuron receptor function together to mediate pheromone signaling.
Specific Aim 2. Correlate the functional peripheral olfactory map to the anatomic map in the Drosophila antenna. We will correlate expression of specific odorant receptor gene products with functional classes of olfactory neurons using a reverse genetic approach. This will allow us to merge the anatomic peripheral olfactory map with the functional map and establish the in vivo odorant specificity for each odorant receptor expressed in the antenna. This information will ultimately help understand how the brain converts odorant blends into meaningful odor images. We will use a transgenic RNAi approach first described by my laboratory to target expression of individual odorant receptors and identify defective functional classes in the transgenic flies using single-sensillum electrophysiological recordings.
Specific Aim 3. Use a Reverse Genetic Approach to elucidate the role of the other OBP proteins expressed in the antenna. We have identified 35 genes encoding OBP proteins in the Drosophila genome. 16 odorant binding proteins are expressed in the antenna. Are all of these proteins mediating pheromone responses or are some involved in detection of general odorants? We will use reverse genetics to eliminate expression of these proteins in the antenna and determine if there are defects in functional classes of olfactory neurons or in mating or aggregation behavior.
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