ATTRACTED OR REPELLED - A MATTER OF 2 NEURONS, ONE PHEROMONE BINDING-PROTEIN, AND A CHIRAL CENTER

Two species of scarab beetles, the Osaka beetle (Anomala osakana) and the Japanese beetle (Popillia japonica), utilize the opposite enantiom ers of japonilure, (Z)-5-(1-decenyl)oxacyclopentan-2-one, as their sex pheromones. Each species produces only one of the enantiomers that fu nctions as its own sex pheromone and as a very strong behavioral antag onist for the other species. Using an integrated approach we tested wh ether the discrimination of these two opposite signals is due to selec tive filtering by pheromone binding proteins or whether it originates in the specificity of ligand-receptor interactions. We found that the antennae of each of these two scarab species contain only a single phe romone binding protein, which associates with both enantiomers to a si milar extent. The single neuron recording technique, on the other hand , showed that both species possess olfactory receptor neurons, colocal ized in one sensillum, extremely specific to either (R)- or (S)-japoni lure. Therefore, pheromone binding proteins (PBPs) alone cannot perfor m the task of chiral discrimination; enantiomeric specificity must be achieved by the interaction of the pheromone or the appropriate ligand -PBP complex with membrane receptors. (C) 1998 Academic Press.