High level expression of "male specific" pheromone binding proteins (PBPs) in the antennae of female noctuiid moths.

Pheromone Binding Proteins (PBPs) are one branch of a multigene family of lepidopteran Odorant Binding Proteins (OBPs) that are known for their relatively high levels of expression in male antennae. However, PBP expression has been observed at low levels in female antennae of the Saturniidae, Bombycidae and Lymantriidae, and at relatively high levels in members of the Noctuiidae. The function of female PBP expression is unclear, as female lepidoptera are consistently noted for their failure to respond physiologically or behaviorally to sex-pheromone. In this study, the sexual dimorphism 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(f). Northern blot analysis indicated relatively high levels of PBP-Hzea(f) expression in both male and female antennae, though females consistently expressed about 50% that of males. Western blot analysis of male and female PBP expression supported these relative differences. Immunocytochemical analysis indicates discrete expression localized beneath olfactory sensilla of both male and female antennae. These results suggest female noctuiids possess the biochemistry to detect at least components of their sex-pheromone. Alternatively, these results may suggest that PBPs have a more general function in noctuiids, possibly reflecting behavioral and life history differences that distinguish this the Noctuiidae from other Lepidopteran families.