Juvenile hormone biosynthesis by corpora allata of larval tomato moth, Lacanobia oleracea, and regulation by Manduca sexta allatostatin and allatotropin

Abstract

Juvenile hormone (JH) biosynthesis and the effects of synthetic Manduca sexta allatostatin (Mas-AS) and M. sexta allatotropin (Mas-AT) were investigated in isolated corpora allata (CA) of Vth stadium larvae of the tomato moth, Lacanobia oleracea. Reversed-phase high-performance liquid chromatography (RP-HPLC) of JH extracted from CA shows that larvae produce predominantly JH II and its corresponding acid. It appears that the acid homologue is a result of JH esterase activity in the CA (and other tissues) rather than the lack of JH acid methyltransferase. Mean rates of synthesis (100–200 fmol/pr/h) were inhibited ca. 70% by Mas-AS and stimulated in a dose-dependent manner up to three times by Mas-AT. However, Mas-AS had no significant effect on Mas-AT-stimulated rates of JH biosynthesis. Using RP-HPLC and an enzyme-linked immunosorbent assay (ELISA) to Mas-AT, a peak of Mas-AT-like immunoreactivity was detected in larval L. oleracea brain homogenates. Co-elution of this immunoreactive peak with synthetic Mas-AT suggests that this neuropeptide is also present in L. oleracea.