Perireceptor Events in Pheromone Perception in Scarab Beetles

Abstract

Despite the remarkable diversity of the sex pheromone chemistry in scarab beetles, various species utilize a common type of γ-lactones in their chemical communication channels. These compounds differ primarily in length of the alkenyl side chain and the stereochemistry at the chiral center. Two species, Anomala osakana and Popillia japonica, utilize the opposite enantiomers of japonilure as sex pheromones. Each species produces only one of the enantiomers that functions as its own sex pheromone and as a behavioral antagonist to the alloreceiver. Pheromone binding proteins (PBPs) have been characterized, which are present in these and several other scarab species. In most cases there was only one class of PBP, which was expressed in both sexes. A. osakana and P. japonica possess each one single PBP with high homology to each other. In each species the same PBP seems to recognize both enantiomers of japonilure, i. e., the pheromonal and the “stop” signals. Based on the N-terminal sequences, the antennae-specific proteins from various other species were highly conserved within the family and showed moderate homology to putative odorant binding protein from Drosophila melanogaster (47%), Lygus lineolaris (45∼50%) and the ABPX protein from Bombyx mori (30∼35%). From analysis of extracts of soluble antennal proteins from several species, significant degradation of the γ-lactones (buibuilactone, japonilure) was detected, essentially in all of them, even in species that do not use these compounds as pheromones. Recently a peculiar pheromone with a diamide moiety [1, 3-dimethyl-2, 4-(1 H, 3 H)-quinazolinedione] was isolated from Phyllopertha diversa, which was rapidly degraded by antennal enzymes from this species. Beetles that utilize lactones as their pheromones possess little or no ability to metabolize this compound.