Opsins and TRP channels controlling sensation and behavior in Aedes aeygpti

Abstract The mosquito Aedes aegypti spreads diseases such as dengue, Zika, yellow fever, and others that afflict >100 million people each year. These mosquitoes rely on multiple keen senses to locate human hosts for blood meals, and for finding conspecifics for mating. Currently, we have only a rudimentary understanding of the receptors that control these critical behaviors. The goal of the proposed research is to address this gap. The unifying theme of this proposal is to test the idea that opsins and TRP channels are two key classes of signaling proteins that have broad roles in sensation and in controlling behavior in Ae. aegypti. Rhodopsins are the founding G-protein coupled receptors (GPCRs). We recently discovered that opsins are multi-modal sensory receptors, challenging 100 years of dogma that they detect only light. To find humans, female Ae. aegypti integrate information from diverse stimuli, including CO2, visual cues, organic molecules, and convection heat from skin. We discovered another cue. Aim 1 builds on our preliminary data that Ae. aegypti use infrared (IR) radiation as an additional host stimulus. We outline experiments to reveal the roles of opsins and the TRPA1 channel in IR detection. We propose to identify the IR-sensing neurons that express the opsins and TRPA1, and to test a model to explain the role of opsins in IR sensation. To pursue this aim, we devised a highly effective assay for monitoring IR attraction and a new molecular genetic approach to bypass difficulties in combining multiple genetic elements. Aim 2 takes advantage of a mutation that we created in another TRP (TRPV-A), which renders males and females deaf. We will test the roles of hearing and TRPV-A in swarm formation, in mating, and in finding humans. Aim 2 will also build on the observations that male mating requires audition mediated by TRPV-A to devise a strategy to overcome a major impediment limiting the efficacy of the sterile insect technique (SIT). SIT is a promising strategy to suppress Ae. aegypti. It involves inundating a local population with sterile males, which then render females sterile upon mating. An obstacle to using SIT is that wild-type males outcompete sterile males. We propose that manipulation of the activity of the TRPV-A- expressing auditory neurons elevates sterile male mating success, and will thereby increase the efficacy of SIT in suppressing Ae. aegypti. Aim 3 concerns identifying the sensory receptors for repellents. We propose to test the idea that an opsin functions as a highly sensitive receptor for insect repellents. If confirmed by the proposed experiments, this would demonstrate that opsins comprise a new class of olfactory receptor. To accomplish our goals, we have developed an extensive repertoire of state-of-the-art approaches. These include new molecular genetic tools, a suite of behavioral assays, original video tracking software, and in vivo electrophysiological recordings. In summary, this project will reveal the roles of opsins and TRP channels in allowing mosquitoes to sense humans and conspecific mates. The insights gleaned from this work have exciting potential to lead to innovative strategies to control Ae. aegypti and reduce insect-borne disease.