Neural and molecular rules of mosquito olfactory rhythms

PROJECT SUMMARY Mosquitoes transmit numerous human pathogens, such as dengue virus and Plasmodium falciparum, collectively responsible for at least one million deaths each year. In addition to rising insecticide resistance and other factors, it has become increasingly evident that current strategies to control mosquito populations are being confounded by the resilience conferred by mosquitoes' high levels of behavioral and physiological plasticity. In particular, biological rhythms are crucial to disease transmission as they allow mosquitoes to be active and responsive to host cues at times of the day when hosts are available. However, despite clear epidemiological relevance, we know very little about the mechanisms underlying the interaction between the chronobiology and the olfactory behavior of mosquitoes. To address this key knowledge gap, we have developed an integrative and multidisciplinary approach that will provide innovative critical steps towards elucidating the neural and molecular rules of sensory processing that guide mosquitoes' olfactory rhythms. We propose here to use this strategy for analyzing the mechanistic underpinnings of the interaction between daily rhythms, olfactory detection and processing, and olfactory-mediated behaviors in Aedes aegypti mosquitoes. We will first determine how rhythms in olfactory sensitivity and in olfactory encoding at the level of the antennal lobe contribute to rhythms in the behavioral responses to host-related volatiles. In a second aim, we will further analyze how circadian clocks modulate the brain and antennal transcriptome of mosquitoes, and generate the first line of arrhythmic mosquitoes, by using CRISPR/Cas9 to knockout clock gene expression. Finally, we will combine behavioral methods and transcriptomic analysis (single-cell RNA sequencing) to identify the cell-types responsible for the synchronization of mosquito behavior with host-availability. This third aim will further provide a large-scale characterization of the rhythmic regulation of mosquito brain activity, and define rhythms in cell regulatory states. Upon completion, these aims will shed light on the neural and molecular processes by which olfactory behaviors vary daily in Ae. aegypti mosquitoes. Not only the proposed work is expected to offer new mechanistic insights into the biological rhythms of mosquitoes and generate a first clock knockout mosquito line, but it also bears strong potential for revealing new targets and methods for disrupting mosquito-host interactions and inform an integrated vector management strategy that can counteract mosquito behavioral plasticity.