Functional validation of the carbon dioxide receptor genes inAedes aegyptimosquitoes using RNA interference

Abstract Carbon dioxide (CO 2 ) is an important long‐range chemosensory cue used by blood‐feeding female mosquitoes to find their hosts. The CO 2 receptor in Drosophila melanogaster was previously determined to be a heterodimer comprised of two gustatory receptor (Gr) proteins, DmGr21a and DmGr63a. In the mosquito Aedes aegypti , two putative orthologous genes, AaGr1 and AaGr3 , were identified in the genome database, along with an apparent paralogue of AaGr1 , AaGr2 . In this study, RNA interference (RNAi)‐mediated gene knockdown of either AaGr1 or AaGr3 resulted in a loss of CO 2 sensitivity in both male and female mosquitoes, suggesting that these two proteins, like the Drosophila orthologues, function as a heterodimer. RNAi‐mediated knockdown of AaGr2 expression had no impact on CO 2 reception. All three Gr genes were expressed in the maxillary palps of both Ae. aegypti and the West Nile virus vector mosquito, Culex pipiens quinquefasciatus . Interestingly, expression of the two CO 2 receptor genes was not equivalent in the two sexes and the implications of differential sex expression of the CO 2 receptor in different species are discussed. The functional identification of the CO 2 receptor in a mosquito could prove invaluable in the strategic design of compounds that disrupt the mosquito's ability to find hosts.