Regulation of sex pheromone biosynthesis in two noctuid species,S. littoralis and M. brassicae,may involve both PBAN and the ventral nerve cord

In order to understand better the mechanism of regulation of pheromone production in moth species, we performed ELISA analyses to detect and follow pheromone biosynthesis activating neuropeptide-like immunoreactivity (PBAN-IR) in different tissues of the two noctuidae species, Spodoptera littoralis and Mamestra brassicae. Male S. littoralis and both male and female M. brassicae brain-subesophageal ganglion (Br-SEG), corpora cardiaca-corpora allata complex, and terminal abdominal ganglion extracts showed the presence of PBAN-IR during both the photophase and the scotophase. However, PBAN-IR was found only in scotophase in female hemolymph. Analysis of extracts of Br-SEG, terminal abdominal ganglion, and hemolymph after HPLC fractionation showed that the most immunoreactive fraction in all the extracts exhibited the same retention time as Hez-PBAN, suggesting that similar PBAN-like material is present in all these tissues. In vivo studies demonstrated that severing the ventral nerve cord in M. brassicae anterior to the terminal abdominal ganglion impaired normal sex pheromone production by third-scotophase females, as was previously shown in S. littoralis. Additionally, PBAN-IR levels were lower in hemolymph samples obtained at the peak of pheromone production in both S. littoralis and M. brassicae females that had the ventral nerve cord severed compared with sham operated animals. These results, along with earlier reported data, indicate that control of pheromone production in both species may involve both PBAN (or PBAN-like peptides) and the ventral nerve cord and support the hypothesis that a neural input from the ventral nerve cord triggers the release of the pheromonotropic peptide(s) into the hemolymph, which then acts directly on the pheromone gland to stimulate pheromone biosynthesis. Arch. Insect Biochem. Physiol. 37:295–304, 1998. © 1998 Wiley-Liss, Inc.

1 We thank Germán Lázaro for insect rearing.