title: Gustatory receptors required for avoiding the insecticide L-canavanine.
abstract: 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.
authors.affiliation: Department of Biological Chemistry, Center for Sensory Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Youngseok
authors.initials: Y
authors.lastname: Lee
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Kang
authors.forename: Jaewon
authors.initials: J
authors.lastname: Shim
authors.forename: Chae Uk
authors.initials: CU
authors.lastname: Cheong
authors.forename: Seok Jun
authors.initials: SJ
authors.lastname: Moon
authors.forename: Craig
authors.initials: C
authors.lastname: Montell
mesh_terms: D000200:Action Potentials / Q000235:genetics / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D001362:Avoidance Learning / Q000187:drug effects / Q000502:physiology*; D002172:Canavanine / Q000494:pharmacology*; D029721:Drosophila Proteins / Q000235:genetics / Q000502:physiology*; D007306:Insecticides / Q000494:pharmacology*; D009154:Mutation; D021122:Protein Subunits / Q000235:genetics / Q000502:physiology; D011956:Receptors, Cell Surface / Q000235:genetics / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D007306:Insecticides; D021122:Protein Subunits; D011956:Receptors, Cell Surface; C405956:gustatory receptor, Drosophila; D002172:Canavanine