Abstract Insects infect hundreds of millions of people annually with deadly viruses and parasites. The goal of the proposed project is to decipher the molecular and cellular mechanisms mediating the insect sense of taste, with the long-term goal of using these insights to develop new insect control strategies. The proposed work will exploit the sophisticated arsenal of tools available for studying the fruit fly, Drosophila melanogaster, to address fundamental questions in the insect taste field. The aims will employ a wide diversity of approaches, including electrophysiology, Ca2+ imaging, behavioral assays, molecular genetics, and cell biology. The project will leverage insights from Drosophila to attack similar problems in the mosquito, Aedes aegypti. The sense of taste is not only essential for mosquito survival, allowing them to discriminate nutritious from dangerous foods, but assists them in making the final decision to bite a human or fly away. Currently, the receptors that function in mosquito taste are largely unknown. In this proposal, we outline experiments focusing on three poorly- understood areas in insect taste: fatty acid taste, amino acid taste, and acid taste. Drosophila find low levels of fatty acids attractive and high levels aversive. The goal of aim 1 is to decipher the receptor and neuronal mechanisms that underlie this discrimination. We will test the model that low fatty acid levels stimulate feeding by activating an amplification cascade initiated by a G-protein coupled receptor and culminating with a TRP channel in cells that stimulate attraction, whereas high levels of fatty acids directly activate a TRP channel in cells that cause repulsion. Fatty acids are potent antifeedants that suppress biting by Aedes. We will test whether the TRP homolog in Aedes aegypti mediates this effect. Aim 2 is to define the receptor and neuronal mechanisms underlying amino acid taste. This is important because flies must consume essential amino acids for growth and egg production. We will test the ideas that: 1) within taste neurons of the fly tongue, a Drosophila TRP senses amino acids in food, and 2) the same TRP detects circulating levels of amino acids in the brain. We will also test the idea that the Aedes TRP homolog is an amino acid sensor. Aim 3 addresses the identity of the proton channel that functions in acid taste. Low levels of some acids are attractive, but high levels are toxic. We will test the idea that a H+ sensor is required in multiple types of taste neurons in the Drosophila proboscis to prevent ingestion of dangerous levels of acids. Acid taste is also important in Aedes to suppress consumption of toxic acids in food, yet carboxylic acids are present in human sweat. We will test whether the Aedes homolog of the Drosophila H+ sensor functions in acid taste. In summary, the proposed research will reveal the receptor mechanisms underlying poorly understood areas in Drosophila taste, and includes the development of a ke...