Submitted to: Journal of Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 1, 2000
Publication Date: N/A
Interpretive Summary: Insects are guided to potential mates and food sources largely by chemical signals, e.g. pheromones and host plant emissions. Noctuiid moth species comprise the most destructive insect pests in agriculture, yet control strategies (primarily insecticidal) are currently limited to larval stages of development. For the Helicoverpa/Heliothis complex of crop pests the use of adult attractants has been largely limited to sex pheromone traps that only yield information on adult male populations. Male moths are especially sensitive to pheromones emitted by females and have developed special cuticular structures to house receptor nerve cells and pheromone binding proteins (PBPs) designed for their detection. We demonstrate conclusively that female noctuiid moths have significant levels of PBP in their noses (antennae). Female PBP is similar to the PBP found in male moths, yet females of Helicoverpa/Heliothis complex lack sensitivity to their own pheromone. PBP in female moths may be involved in detection of pheromone emissions of other female species to avoid crowding or other odors important in species propagation, e.g. plant odors important in locating oviposition sites. Entomologists and molecular biologists interested in olfactory mechanisms, mating disruption and census strategies, may use this new knowledge.
Technical Abstract: Pheromone Binding Protiens (PBPs) are a subclass of Lepidopteran Odorant Binding Proteins (OBPs), PBPs are the only group that is noted for its sexually dimorphic expression. While PBPs are consistently observed to be strongly expressed in male antennae, the level of their expression in female antennae varies among those species studied, ranging from undetectable in members of the Saturniidae and Lymantriidae to relatively strong female expression in certain Noctuiidae. In this study, the sexual dimoprhism of PBP expression was examined in the noctuiid moths, Helicoverpa zea, Heliothis virescens and Spodoptera frugiperda. A PBP cDNA clone was isolated from female H. zea: PBP-Hzea. Northern blot analysis indicates similar levels of expression in both male and female antennae, though females consistently express about 50% of that of males. Western blot analysis of male and female expression in H. zea, H. virescens and S. frugiperda support these relative differences in PBP expression. Immunocytochemical analyses of the distributions of olfactory sensilla in male and female antennae of S. frugiperda indicate specific expression of PBP; this expression defined the largest subclass of sensilla in both sex antennae. Together with data from other noctuiids, these results suggest female noctuiids possess the biochemistry to detect at least components of their sex-pheromone. Alternatively, in light of many studies indicating that noctuiid females are unable to respond electrophysiologically or behaviorally to sex-pheromones, these results may suggest that PBPs have a more general function in noctuiids, possibly reflecting behavioral and life history differences which define respective Lepidopteran families.