Cellular and molecular mechanisms that regulate olfactory rhythms in drosophila melanogaster

Abstract

This dissertation is focused on how circadian control of olfactory responses are regulated at the cellular and molecular level in Drosophila. Electrophysiological approaches consisting of Electroantennogram (EAG), single unit recordings, among other techniques, were used to investigate the extent of autonomy of peripheral oscillators from central pacemaker cells, the molecular targets of the circadian oscillator in antennal neurons, and the nature of circadian influence on single unit responses recorded from basiconic sensillae. To address the question of cellular mechanisms mediating olfaction rhythms, UAS-Gal4 strategies were used for tissue specific expression of dominant negative forms of CLK (CLOCK) and CYC (CYCLE). Specifically, OR (Odorant Receptor)- GAL4 constructs were used to achieve cell specific expression in the antenna. By recording EAG responses from specific regions of the antenna, it was found that antennal sensory neurons possess independent oscillators that are both necessary and sufficient to drive rhythms in olfactory responses. To understand the molecular mechanisms controlling olfaction rhythms, the effect of GRK-2 and an arrestin (KURTZ) of the olfactory signal transduction pathway were studied by use of respective mutants and the effect of cell specific rescue of these proteins by UAS-Gal4 approaches was also documented. Interestingly, these molecules have phenotypes that argue for a different role of for these proteins in Drosophila olfaction as opposed to their respective functions in vertebrate systems. Finally, single unit recordings were measured from different basiconic sensilla and the influence of the circadian oscillator was studied on select parameters of the single unit data obtained. It was found that spike amplitude of the spontaneous response was the only parameter under circadian control and that these rhythms are dependant on input from the odorant receptor activated pathway.