ACHEMS 2019
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SPLTRAK Abstract Submission
Feeding control via multimodal taste integration in pharyngeal neurons in adult Drosophila  
Yu-Chieh D. Chen1, Ryan M. Joseph2, Anupama A. Dahanukar1,2
1Interdepartmental Neuroscience Program, UC Riverside, Riverside, CA, United States
2Department of Molecular, Cell and Systems Biology, UC Riverside , Riverside, CA, United States

In adult Drosophila, tastants are detected via taste sensilla in multiple organs throughout the body, present externally in the labellum, legs, wings and internally in the pharynx. Taste input originating from multiple classes of gustatory receptor neurons (GRNs) in different taste organs is thought to be processed in higher-order brain circuits for mediating behavioral output, yet how pharyngeal GRNs that are positioned at a crucial site for food evaluation contribute to feeding behavior remains unclear. We used a Pox-neuro (Poxn) mutant as a minimal taste system model in which all the external taste sensilla are transformed into mechanosensory sensilla, while all pharyngeal GRNs remain intact. In Poxn mutants, we genetically silenced all pharyngeal GRNs and found that feeding attraction to appetitive tastants and avoidance of aversive tastants were both abolished in binary choice assays, suggesting a key role for pharyngeal taste in food selection. Guided by our recent pharyngeal chemoreceptor reporter map, we used genetic intersectional strategies to selectively protect molecularly defined class of pharyngeal GRNs in otherwise taste-blind flies, allowing us test principles of taste coding and behavior in animals that possess only one type of taste neuron. Using single-fly quantitative FLIC assays to measure various micro-feeding parameters, we found that flies with distinct single classes of pharyngeal GRNs exhibited distinct, and in some cases opposing, micro-feeding behaviors in response to the same tastants. Further, Ca2+ imaging of selected pharyngeal GRNs revealed overlap in tastant sensitivity, as well as multimodal tastant-sensing properties. Together, our results suggest that distinct populations of pharyngeal GRNs can control micro-feeding parameters in synergistic or antagonistic ways.