Distinct sweet taste receptor neurons in the legs of Drosophila

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The ability to detect and elicit appropriate behavioural responses to palatable stimuli is important for the survival of all animals. In Drosophila, contact-based detection of sweet chemical substances is mediated by gustatory organs that are distributed throughout the fly body, including the proboscis and legs. Taking advantage of a rich variety of genetic techniques, Drosophila melanogaster has served as an excellent model system to study basic principles of the structure and function of the gustatory system. Nevertheless, fundamental questions remain to be answered: Do different gustatory sensory neurons fulfill specific functions? How is sweet taste computed in the fly brain to elicit appetitive behaviour? How does detection of sugar lead to different aspects of appetitive behaviour (e.g. proboscis extension, appetitive reinforcement)?Our initial observations revealed that a small subset of morphologically distinct tarsal sensory neurons is particularly important in driving appetitive responses to sucrose. Using sophisticated genetic intervention strategies, I propose to comprehensively characterise individual tarsal neurons. To this end, we will generate transgenic flies that allow us to specifically label and manipulate distinct tarsal sweet taste receptors, and identify their functions in different sugar response behaviours. As a first step toward cellular mechanisms of sweet taste processing in the fly, we aim to efficiently identify downstream neurons of the sugar sensory neurons and investigate their anatomical connections to higher-order components of the taste circuit. Taken together, these experiments will contribute to the construction of functional circuit maps underlying sugar response in Drosophila.