SPLTRAK Abstract Submission
The Fat Tastes Different: The Perception and Discrimination of Fatty Acids in Drosophila
Pavel Masek1, Yuanyuan Li1, Alex Keen2, John Tauber2, Elizabeth Brown2, Jake Gordon1
1Binghamton University, Binghamton, NY, United States
2FAU, Jupiter, FL, United States

Fat represents the most calorically potent food source per unit of mass. Previously, we showed that a broad population of sugar-sensing taste neurons expressing Gustatory Receptor 64f (Gr64f), is required for reflexive feeding responses to sugars but also to free fatty acids (FAs), one of the building blocks of fat. A functional Phospholipase C pathway in these neurons is specifically needed only for FAs perception. The detection of different chemicals through the same neurons but through different biochemical pathways was described in other insects but the implication of this separation remains unclear. We now describe specific populations of taste neurons mediating FA taste that are identified by expression of Ionotropic Receptor 56d (IR56d). IR56d together with IR76b and IR25a are necessary for perception of FAs. Functional imaging reveals that these neurons response to short- and medium-chain FAs and are necessary and sufficient to drive the feeding responses. Behaviorally, we show that flies display different response to FAs and sugars relative to their intensity. They show increasing preference to sugars with increasing concentration but prefer FAs at low concentrations and avoid them at high, likely due to involvement of bitter sensing neurons. Flies can also discriminate between sugars and FAs using an aversive taste memory assay. These results support the notion that the taste of FAs is a unique taste modality. We further test discrimination between multiple FAs from various categories including medium and long carbon chain; saturated, mono and poly unsaturated. Here we describe different modes of tastants discrimination that allows us to categorize appetitive taste stimuli into functional groups and will help us to further understand the diversity in the taste modalities.