Identification of ecdysis-triggering hormone from an epitracheal endocrine system

Department of Entomology, University of California, Riverside 92521, USA.
Science (Impact Factor: 31.48). 02/1996; 271(5245):88-91. DOI: 10.1126/science.271.5245.88
Source: PubMed

ABSTRACT 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.

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    • "In this study, analysis of the test insect fed with C. microphylla extracts, revealed a developmental disruption in which the insects died (between 10 and 25 ppm) during pharate conditions after initiation of molting (the apolysis step), without completion of morphogenesis . During a molt, ecdysteroid levels first rise to stimulate onset of apolysis and cuticle synthesis, but then must fall to facilitate the release of eclosion hormone (EH) (Truman et al., 1983; 2002) and the ecdysis-triggering hormone (ETH) (Zitnan et al., 1996, 1999). These last substances act in concert to trigger insect ecdysis during the final stages of the molt. "
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    Industrial Crops and Products 03/2013; 42(1):78-86. DOI:10.1016/j.indcrop.2012.05.002 · 2.84 Impact Factor
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    • "Instead, neurosecretory cells that send axons to a release site are located mainly in the pars intercerebralis, but some are also located in the pars lateralis or tritocerebrum, in the suboesophageal and/or ventral ganglia. Non-neuronal Inka cells that produce the releasing hormone ecdysis-triggering hormone (ETH) are located on the surface of insect tracheae [102]. The gut is also a site of synthesis and release (into the hemolymph) of some brain-gut peptides. "
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    General and Comparative Endocrinology 03/2012; 177(1):18-27. DOI:10.1016/j.ygcen.2012.02.002 · 2.67 Impact Factor
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    • "in Manduca sexta [30] [31] and Drosophila melanogaster [20] [22]. Blood-borne ETHs initiate the ecdysis sequence through direct actions on the central nervous system (CNS) [30] [31]. Discovery of ETH receptor genes in Drosophila [12] [23] and Manduca [13] facilitated identification of many neuronal targets of ETH within the CNS. "
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    ABSTRACT: Ecdysis triggering hormones (ETHs) from endocrine Inka cells initiate the ecdysis sequence through action on central neurons expressing ETH receptors (ETHR) in model moth and dipteran species. We used various biochemical, molecular and BLAST search techniques to detect these signaling molecules in representatives of diverse arthropods. Using peptide isolation from tracheal extracts, cDNA cloning or homology searches, we identified ETHs in a variety of hemimetabolous and holometabolous insects. Most insects produce two related ETHs, but only a single active peptide was isolated from the cricket and one peptide is encoded by the eth gene of the honeybee, parasitic wasp and aphid. Immunohistochemical staining with antiserum to Manduca PETH revealed Inka cells on tracheal surface of diverse insects. In spite of conserved ETH sequences, comparison of natural and the ETH-induced ecdysis sequence in the honeybee and beetle revealed considerable species-specific differences in pre-ecdysis and ecdysis behaviors. DNA sequences coding for putative ETHR were deduced from available genomes of several hemimetabolous and holometabolous insects. In all insects examined, the ethr gene encodes two subtypes of the receptor (ETHR-A and ETHR-B). Phylogenetic analysis showed that these receptors fall into a family of closely related GPCRs. We report for the first time the presence of putative ETHs and ETHRs in genomes of other arthropods, including the tick (Arachnida) and water flea (Crustacea). The possible source of ETH in ticks was detected in paired cells located in all pedal segments. Our results provide further evidence of structural and functional conservation of ETH-ETHR signaling.
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