SPLTRAK Abstract Submission

The taste of RNA in insects




Ji-Eun Ahn1, Dushyant Mishra2, Christopher Jagge1, Chika Miyamoto1, Hubert Amrein1
1Texas A&M University Health Science Center, College Station, TX, United States
2University of Connecticut, Storrs, CT, United States

Most animals employ various types of taste receptors to identify essential macronutrients, such as sugars, amino acids and fats, as well as noxious compounds generally perceived as bitter. Drosophila has emerged as the main insect model system for functional analyses of taste receptors and the neural circuitry of taste behavior, and receptors for sugars, bitter chemicals, acids, fatty acids and proteins have been identified. Here, we report that Drosophila and other insect larvae exhibit appetitive taste behavior for RNA and ribonucleosides. We show that RNA and ribonucleosides are essential nutrients for Drosophila to support accelerated growth and survival during the larval stages. Moreover, we find that the Gustatory receptor 28 (Gr28) gene subfamily encode receptors for RNA and ribonucleosides through the ribose moiety in these chemicals. CAMPARI based Ca2+ imaging established that terminal organ taste neurons respond to ribose, inosine, uridine and tRNA in Gr28-dependent manner. Finally, heterologous expressions of single Gr28 genes in fructose-sensing neurons which do not express any of the Gr28 genes, conveys responses to ribose and RNA and can rescue attraction to these chemicals in homozygous mutant Gr28 larvae. To examine whether RNA taste is a general insect modality, we examined larval preference behavior of the blowflies L. cuprina and C. rufifacies and the mosquito A. aegypti. Larvae of all three species show strong attraction to ribose and RNA. Finally, expression of A. aegypti Gr9a, a Gr28 homolog, in Drosophila taste neurons rescues appetitive behavioral responses to ribose and RNA of Gr28 mutant larvae. Our studies have uncovered a new nutrient for insect larvae, RNA, and identified Gr28 proteins as the molecular receptors.