Comparative functional and neuroanatomical analyses of olfactory circuit in drosophilids
Animals have adapted to their ecological niche by developing unique behavioral strategies. However, little is known about the underlying changes in neuronal circuit structure and/or function. To understand how evolution might modify nervous systems, I propose to perform comparative neurobiological analyses of the anatomy and physiology of central olfactory circuitry in two drosophilid species (Drosophila sechellia and D. melanogaster), which have adapted to different niches and display distinct odor-evoked behaviors. Although several changes in peripheral, sensory neuron properties have been observed between these species, the function and evolution of central circuitry has not yet been examined. The architecture and the neuronal coding properties of the primary olfactory center (antennal lobe; AL) of D. melanogaster is well-characterized and thus serves as an excellent “reference” for interspecies comparison. Using new neurogenetic approaches in D. sechellia, I will first use calcium imaging to record physiological responses in the AL to volatile cues evoking short- and long-range attraction behavior. Second, I will trace the projections of second-order olfactory neurons to higher brain centers using genetically-encoded photoactivable markers and/or trans-synaptic tracers. Third, I will study the structure and function of these central pathways in odor-evoked attraction by combining trans-synaptic labeling and optogenetics. Together, these experiments will help us understand how different olfactory pathways mediate long and short range attraction and how they are modified during evolution to confer species-specific behavioral outputs.