Activation of Manduca sexta corpora allata in vitro by a cerebral neuropeptide.

When an in vitro assay system and radioimmunoassays specific for juvenile hormones (JH) I and III were used to probe the effect of co-incubating pupal brains with last instar larval corpora allata (CA) from the tobacco hornworm, Manduca sexta, a selective activation of JH III synthesis by the CA was observed. This homolog-specific activation suggested the presence of an allatotropic factor for the synthesis of JH III (JH III ATF), and its presence was demonstrated by the ability of a postmicrosomal supernatant of a day 0 pupal brain homogenate to activate the CA in vitro in a dose-dependent manner. This moiety appears to be a protein, based on its heat lability and protease sensitivity, and has an apparent molecular size of 40 kD and an isoelectric point of 5.5 JH III ATF activity is localized in specific neural tissues of the day 0 pupa, the brain and first three abdominal ganglia, with the brain containing 4 times the activity in the ganglia. The existence of this factor suggests that JH III synthesis by the CA of Manduca is regulated by a neuropeptide.