Project Summary As one of the most important vectors for the malaria parasite Plasmodium falciparum, which infected approximately 228 million people worldwide in 2018 and accounted for more than 400,000 deaths (WHO, 2019), the An. coluzzii mosquito has long been a formidable concern to public health. These mosquitoes rely heavily on their chemosensory system to detect chemical cues involved in the mating process, including aggregation pheromones and cuticular hydrocarbons. Swarm aggregation pheromones increase the possibility of encountering female mosquitoes while cuticular hydrocarbons help male mosquitoes recognize conspecific females. A recent finding of ours indicated that not only were Gr23-null mutants insensitive to carbon dioxide stimulation, they also appeared to have some mating defect, as they failed to self-breed. Previous transcriptomic studies in Aedes mosquitoes indicated that Gr23 is expressed in CO2-sensitive neurons in the maxillary palps, but presents the highest expression among all gustatory receptors in the antennae and other chemosensory appendages, which suggests additional roles of Gr23 in chemosensation beyond CO2 reception. Therefore, the aim of this research proposal is to determine the role of Gr23 in the mating capacity of An. coluzzii. Here, we hypothesize that the observed self-breeding defect of Gr23 mutants is due to their inability to detect mating-related chemical cues, and that the Gr23 receptor plays a critical role in this chemosensory process. Accordingly, the fundamental questions I propose to address are: (1) what is the expression pattern of Gr23 in the chemosensory neurons of the mating-related appendages in An. coluzzii? (2) What is the molecular function of Gr23 in detecting the mating-related semiochemicals? In addressing these questions, this work will further our understanding of the role of Gr23 in the mosquito's odor-mediated mating process, which would have great potential as a novel molecular target in mosquito control.