Structural characterization and expression analysis of prothoracicotropic hormone in the corn earworm, Helicoverpa zea

The cDNA encoding prothoracicotropic hormone (PTTH), the brain neuropeptide that stimulates the prothoracic glands to synthesize ecdysone, was cloned from the corn earworm Helicoverpa zea (Hez). The amino acid sequence deduced from the cDNA indicates a molecular structure that is distinct from the PTTH's reported in other Lepidoptera, but all contain an identical proteolytic cleavage site and the seven cysteine residues that are essential for activity. Northern hybridization shows a single mRNA present in the brain-subesophageal ganglion complex. Using RT-PCR, we observed constant amounts of PTTH mRNA during larval development but large fluctuations at pupation and prior to adult eclosion.