Contribution of neurons that express fruitless and Clock transcription factors to behavioral rhythms and courtship

Animals need to integrate information across neuronal networks that direct reproductive behaviors and circadian rhythms. In Drosophila, the master regulatory transcription factors that direct courtship behaviors and circadian rhythms are co-expressed in a small set of neurons. In this study we investigate the role of these neurons in both males and females. We find sex-differences in the number of these fruitless and Clock -expressing neurons (fru {cap} Clk neurons) that is regulated by male-specific Fru. We assign the fru {cap} Clk neurons to the electron microscopy connectome that provides high resolution structural information. We also discover sex-differences in the number of fru-expressing neurons that are post-synaptic targets of Clk-expressing neurons, with more post-synaptic targets in males. When fru {cap} Clk neurons are activated or silenced, males have a shorter period length. Activation of fru {cap} Clk neurons also changes the rate a courtship behavior is performed. We find that activation and silencing fru {cap} Clk neurons impacts the molecular clock in the sLNv master pacemaker neurons, in a cell-nonautonomous manner. These results reveal how neurons that subserve the two processes, reproduction and circadian rhythms, can impact behavioral outcomes in a sex-specific manner.