고려대학교 생명과학대학 생명과학부/ 대학원 분자생명과학과

Animals find nutritious foods to survive, while avoiding aversive and toxic chemicals through the chemosensory faculties of olfaction and taste. The olfaction is comparatively well char­acterized, but the studies of taste are only recently developing since after 2000. Genetic, immunohistochemistry, and electrophysiological studies with knock-out transgenic mice opened up the taste field in mammals. Taste in insects has been only recently been studied after mammalian taste receptors were identified. Flies also discriminate the differences of sweet, salty and sour food, while being able to detect and reject potential foods contami­nated with toxins or detrimental chemicals. These discriminatory abilities indicate that flies house basic taste receptors in their taste organs like humans. For the last decade, the sweet and bitter gustatory receptors in Drosophila have been characterized. In this presentation, I compare the taste anatomy between humans and insects. I also introduce five canonical taste sensations in Drosophila. In addition, we introduce new taste repertoires, that fruit flies can sense water and fatty acids as well as the carbonation buffer in beverage. These studies on simple model organisms will open up a new potential for scientists to further investigate these characteristics in vertebrates.

Most recently, I reported that three gustatory receptors, GR8a, GR66a, and GR98b function together in the detectionofL-canavanine, a plant-derived insecticide. Ectopic co-expression of Gr8a and Gr98b in Gr66a-expressing, bitter-sensing gustatory receptor neurons (GRNs) confer responsiveness to L-canavanine. Furthermore, mis-expression of all three Grs enabled salt- or sweet-sensing GRNs to respond to L-canavanine. Introduction of these Grs in sweet-sensing GRNs switch L-canavanine from an aversive to an attractive compound. Co-expression of GR8a, GR66a, and GR98b in Drosophila S2 cells induce an L-canavanine-activated nonxxxive cation conductance. I conclude that three GRs collaborate to produce a functional L-canavanine receptor. Thus, my results clarify the full set of GRs underlying the detection of a toxic tastant that drives avoidance behavior in an insect.