THE PROTHORACICOTROPIC HORMONE (PTTH) OF THE COMMERCIAL SILKMOTH, BOMBYX-MORI, IN THE CNS OF THE TOBACCO HORNWORM, MANDUCA-SEXTA

Immunocytochemistry revealed that a Bombyx mori prothoracicotropic hor mone (PTTH)-like peptide is expressed by the Manduca sexta big PTTH-pr oducing neurons, the lateral neurosecretory cell group III (L-NSC III) . Independent PCR of genomic DNA and a L-NSC III cDNA library yielded products with 99% sequence similarity to the cDNA encoding Bombyx PTTH . This similarity necessitated evaluation of the relationship between Manduca big PTTH and Bombyx PTTH by 1) bioassay of IEF separated Mandu ca PTTH and 2) direct assessment of Bombyx PTTH biological activity wi th Manduca prothoracic glands. Together, these studies indicate that B ombyx PTTH and Manduca PTTH are different peptides expressed by the L- NSC III. The possible physiological significance of a Bambyx PTTH-like peptide in Manduca and its coexpression with Manduca big PTTH by the L-NSC III are discussed.