Gustatory receptors required for avoiding the insecticide L-canavanine

• Published in: The Journal of neuroscience Vol. 32; no. 4; pp. 1429 - 1435
• Main Authors: Lee, Youngseok, Kang, Min Jung, Shim, Jaewon, Cheong, Chae Uk, Moon, Seok Jun, Montell, Craig
• Format: Journal Article
• Language: English
• Published: United States Society for Neuroscience 25.01.2012
• Subjects: Action Potentials - genetics; Action Potentials - physiology; Animals; Animals, Genetically Modified; Avoidance Learning - drug effects; Avoidance Learning - physiology; Canavanine - pharmacology; Drosophila Proteins - genetics; Drosophila Proteins - physiology; Insecticides - pharmacology; Mutation; Protein Subunits - genetics; Protein Subunits - physiology; Receptors, Cell Surface - genetics; Receptors, Cell Surface - physiology
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/jneurosci.4630-11.2012

Insect survival depends on contact chemosensation to sense and avoid consuming plant-derived insecticides, such as L-canavanine. Members of a family of ∼60 gustatory receptors (GRs) comprise the main peripheral receptors responsible for taste sensation in Drosophila. However, the roles of most Drosophila GRs are unknown. In addition to GRs, a G protein-coupled receptor, DmXR, has been reported to be required for detecting L-canavanine. Here, we showed that GRs are essential for responding to L-canavanine and that flies missing DmXR displayed normal L-canavanine avoidance and L-canavanine-evoked action potentials. Mutations disrupting either Gr8a or Gr66a resulted in an inability to detect L-canavanine. We found that L-canavanine stimulated action potentials in S-type sensilla, which were where Gr8a and Gr66a were both expressed, but not in Gr66a-expressing sensilla that did not express Gr8a. L-canavanine-induced action potentials were also abolished in the Gr8a and Gr66a mutant animals. Gr8a was narrowly required for responding to L-canavanine, in contrast to Gr66a, which was broadly required for responding to other noxious tastants. Our data suggest that GR8a and GR66a are subunits of an L-canavanine receptor and that GR8a contributes to the specificity for L-canavanine.