Receptor-enabled Approach to Identify Chemicals to Repel Mosquitoes

This project will seek to clarify the receptor mechanisms through which the mosquito, Aedes (Ae.) aegypti, detects gustatory cues. Taste is critical for allowing mosquitoes to discriminate safe from toxic sources of nectar. Gustatory cues constitute the final sensory information gathered by female Aedes before they decide whether or not to take a blood meal. Despite the importance of taste for the survival of mosquitoes, our understanding of the functions of different gustatory receptor neurons (GRNs), and the receptors is rudimentary.

In Ae. aegypti, the largest mouthparts consist of two bilaterally symmetrical labella, which are situated at the end of a long sheath. The labium also houses the fascicle, which is comprised of a set of needle-like stylets. In females, one of the six stylets, the labrum, contains neurons that sense constituents in blood, and is also used to withdraw the blood meal. Most of the hair-like (trichoid) sensilla decorating the labella contain our GRNs. However, the functions of the different GRNs have not been clarified.

During the first 3 years of this project, we seek to accomplish two major objectives. The first is to define the functions of the different classes of GRNs in Ae. aegypti. To accomplish this goal, we will create genetically-encoded gene drivers to direct expression of transgenes in different classes of GRNs. This will allow us to express a transgene encoding an inward-rectifier K+ channel (QUAS-kir2.1) that we created in Ae. aegypti, which will inactivate different classes of GRNs. We will then assess the effects of inactivating different classes of GRNs using behavioral and electrophysiological assays. Our second major objective is to define the roles of putative taste receptors in Aedes that are homologs of known taste receptors in Drosophila. The selected candidates fall into five classes: TRP channels, Gustatory Receptors (GRs), Ionotropic Receptors (IRs), Pickpockets (Ppks), and opsins, the latter of which we have recently found to be a surprising class of taste receptor in Drosophila.

In addition to being attracted to chemicals on skin, the ability of female Aedes to probe for veins for blood meals is likely dependent at least in part on mechanosensation, since superficial veins have different mechanical properties from skin. Our vision for the last two years of this project is to identify the relevant mechanosensory channel(s). We suggest that this project will transform our very limited understanding of taste in mosquitoes by defining the roles of neurons and receptors/channels that are critical for feeding on botanical food sources, and on blood.