Characterization of drosophila bitter receptors for L-canavanine

Abstract

Plants often produce insecticides to protect themselves from predators, including insects. Some insects can detect insecticides and avoid ingestion through a contact chemosensory system. Members of a family of 68 gustatory receptors (GRs) make up the main taste receptors responsible for taste sense in Drosophila. However, the molecular identity of Drosophila GRs remains unknown. It has been reported that one of the G-protein coupled receptors (GPCRs), DmXR, is required for detecting L-canavanine as an aversive tastant (Mitri et al., 2009). Here, I report that Drosophila GRs are involved in L-canavanine sensing. The mutation in the gustatory receptors Gr8a and Gr66a resulted in a complete inability to detect L-canavanine. Gr8a is expressed in a subset of Gr66a-expressing gustatory receptor neurons (GRNs). L-canavanine can stimulate s-type sensilla where Gr8a is expressed, but not in all Gr66a-expressing GRNs. L-canavanine-induced action potentials were abolished in the Gr8a and Gr66a mutant animals. These data suggest that Gr8a and Gr66a are L-canavanine co-receptors, while Gr8a may determine the specificity for L-canavanine.