Molecular characterization and cell-specific expression of an ion transport peptide in the tobacco hornworm, Manduca sexta.
The crustacean hyperglycemic hormone (CHH) peptides regulate diverse physiological processes from reproduction to metabolism and molting in arthropods. In insects, the ion transport peptides (ITP), also members of the CHH family, have only been implicated in ion transport. In this study, we sequenced a nucleotide fragment spanning the conserved A1/A2 region of the putative CHH/ITP gene. This fragment was amplified from larval cDNA of the tobacco hornworm, Manduca sexta and showed a high degree of sequence conservation with the same region from other insects and, to a lesser degree, with that of crustacean species, suggesting the presence of a Manduca-specific CHH/ITP mRNA (MasITP mRNA). CHH-like immunocytochemical analyses with two crustacean antisera (from Carcinus maenas and Cancer pagurus) identified the presence of CHH-like immunoreactivity in nervous tissue of all developmental stages, but not in the gut of M. sexta. Specifically, CHH-like peptides localized to paired type IA(2) neurosecretory cells of the pars lateralis of the brain (projecting ipsilaterallly to the corpora cardiaca-allata complex) and to neurosecretory cells and transverse nerves of the ventral nerve cord in larvae, pupae, and adults. The distribution of the putative MasITP peptide shifted during development in a manner consistent with metamorphic reorganization. A comparison of hemolymph equivalents of CHH detected by enzyme-linked immunosorbent assay with CHH-like immunoreactivity in transverse nerves provided evidence for the release of MasITP from the transverse nerves into the hemolymph at insect ecdysis. These data suggest the presence of an insect ITP in M. sexta and a role for this hormone during ecdysis.
Drexler
Anna L
AL
Department of Biology, San Francisco State University, San Francisco, CA 94132, USA.
Harris
Christina C
CC
dela Pena
Myra G
MG
Asuncion-Uchi
Marilyn
M
Chung
Sook
S
Webster
Simon
S
Fuse
Megumi
M
D000595:Amino Acid Sequence; D000818:Animals; D060829:Arthropod Proteins; D001483:Base Sequence; D002490:Central Nervous System / Q000378:metabolism; D017124:Conserved Sequence; D006458:Hemolymph / Q000378:metabolism; D007150:Immunohistochemistry; D007447:Invertebrate Hormones / Q000097:blood / Q000378:metabolism*; D017136:Ion Transport; D007814:Larva / Q000378:metabolism; D018402:Manduca / Q000254:growth & development / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000097:blood / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D011863:Radioimmunoassay
D060829:Arthropod Proteins; D007447:Invertebrate Hormones; D009419:Nerve Tissue Proteins; D010455:Peptides; C015947:hyperglycemic hormone, crustacean