Abstract
Drosophila circadian rhythms are regulated by an endogenous circadian clock located in about 150 pacemaker neurons in the fly brain. These pacemakers express key circadian proteins such as PERIOD (PER) and TIMELESS (TIM). Here we utilized a newly developed calcium reporter to real-time monitor the neuronal activity of key circadian pacemakers. As expected, we found that the master circadian pacemakers, morning cells, exhibited a self-sustained calcium oscillation that peaked around lights on and was maintained in constant darkness. This cycling pattern was affected by light conditions and more interestingly, by mating. Virgins showed a calcium cycling pattern similar to that observed in males while mated females exhibit an increased amplitude and anti-phase calcium oscillations, which may be related to egg-laying behavior. In addition, we exploited a video recording assay combined with an optogenetic tool to simultaneously record and manipulate fly behavior. We verified that this assay can faithfully record fly locomotor patterns and activate the key circadian pacemakers to produce different behavior outputs. Although this work was done in collaboration with Dr. Fang Guo, my specific contributions were to 1) recognize the importance of mating to female behavior, 2) build and fine-tune the LED-video system for neuron stimulation and 3) begin the analysis of wake-promoting neurons with this system. The important tools described here will allow us to make the underlying links between neuronal circuits and different behaviors in Drosophila and ultimately construct the neuronal network at the cellular level.