UC Riverside

Drosophila melanogaster feed, mate and lay eggs on fermented compounds. Feeding on caloric-non-toxic foods is ideal, however flies primarily feed upon mixtures including attractive and aversive compounds. Investigating taste detection mechanisms is vital to understand feeding preferences. Utilizing Drosophila we have a unique opportunity to connect mechanisms of taste receptor function to feeding behaviors. We find that Drosophila exhibits a strong feeding behavior towards beer. Specifically, our data demonstrate that feeding preference towards fermentation products is dependent on gustatory receptor Gr64e, a receptor for glycerol. Glycerol is an attractive compound in yeast-fermented foods. Furthermore, Drosophila species that lack a functional copy of Gr64e have reduced responses to glycerol. Our data provide evidence that Gr64e may contribute to evolutionary shifts in food selection in Drosophila species.

We are beginning to understand gustatory receptor (Gr) response profiles, however mechanisms by which Grs function to encode specific compounds remain largely unknown. Peripheral detection of attractive compounds, such as sugars, is crucial for eliciting proper feeding behaviors. There are eight conserved Grs in the sweet clade expressed by sweet neurons. We characterize five Gr mutants using a panel of sweet compounds and find that each Gr mutant shows a loss in response profile to a sweet panel. In turn, these mutant data correlate with ectopic expression of corresponding single Grs in a novel in vivo system. Taken together our results indicate each Gr contributes to sugar detection and sugars can activate multiple Grs.

In addition to sugars, aversive compounds are also found in complex stimuli. Little is known about how flies taste acids despite their common occurrence in fruit sources. Here we explore the mechanism of acid detection in Drosophila and find that flies strongly avoid acids per detection by a subset of bitter neurons. Furthermore, bitter neurons exhibit dose dependent activity increases in response to decreasing pH. Overall, our data sets a foundation for acid detection in Drosophila and facilitates further investigations for acid receptor identity. Our research demonstrates the power of Drosophila as a model system to characterize peripheral taste detection aiming to further understand how taste receptors function to encode taste compounds.