Identification of ecdysis-triggering hormone from an epitracheal endocrine system.
Developing insects repeatedly shed their cuticle by means of a stereotyped behavior called ecdysis, thought to be initiated by the brain peptide eclosion hormone. Here an ecdysis-triggering hormone, Mas-ETH, is described from the tobacco hornworm Manduca sexta. Mas-ETH contains 26 amino acids and is produced by a segmentally distributed endocrine system of epitracheal glands (EGs). The EGs undergo a marked reduction in volume, appearance, and immunohistochemical staining during ecdysis, at which time Mas-ETH is found in the hemolymph. Injection of EGs extract or synthetic Mas-ETH into pharate larvae, pupae, or adults initiates preecdysis within 2 to 10 minutes, followed by ecdysis. Sensitivity to injected Mas-ETH appears much earlier before ecdysis and occurs with shorter latency than that reported for eclosion hormone. The isolated central nervous system responds to Mas-ETH, but not to eclosion hormone, with patterned motor bursting corresponding to in vivo preecdysis and ecdysis. Mas-ETH may be an immediate blood-borne trigger for ecdysis through a direct action on the nervous system.
Department of Entomology, University of California, Riverside 92521, USA.
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Zitnan
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Kingan
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Hermesman
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ME
Adams
D000595:Amino Acid Sequence; D000818:Animals; D002490:Central Nervous System / Q000187:drug effects / Q000502:physiology; D004702:Endocrine Glands / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D006458:Hemolymph / Q000737:chemistry; D007301:Insect Hormones / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins; D007814:Larva / Q000502:physiology; D018402:Manduca / Q000737:chemistry* / Q000502:physiology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018978:Molting; D009046:Motor Neurons / Q000187:drug effects / Q000502:physiology; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology / Q000502:physiology*; D011679:Pupa / Q000502:physiology
D007301:Insect Hormones; D036341:Intercellular Signaling Peptides and Proteins; C097515:Manduca sexta ecdysis-triggering hormone; D010455:Peptides; C042645:eclosion hormone