title: Amino acids and TOR signaling promote prothoracic gland growth and the initiation of larval molts in the tobacco hornworm Manduca sexta.
abstract: Molting in arthropods is orchestrated by a series of endocrine changes that occur towards the end of an instar. However, little is understood about the mechanisms that trigger these endocrine changes. Here, nutritional inputs were manipulated to investigate the minimal nutritional inputs required for a Manduca sexta larva to initiate a molt. Amino acids were found to be necessary for a larva to molt, indicating the involvement of an amino acid sensitive pathway. Feeding rapamycin, an inhibitor of the target of rapamycin (TOR) signaling, delayed the onset of a molt and resulted in abnormally larger larvae. Rapamycin also suppressed the growth of the prothoracic glands relative to the whole body growth, and this was accompanied by suppression of ecdysone production and secretion. Higher doses of rapamycin also slowed the growth rate, indicating that TOR signaling also plays a role in systemic growth. TOR signaling therefore couples the nutritional status of the larva to the endocrine system to regulate the timing of a molt.
authors.affiliation: Department of Biological Sciences, Wellesley College, Wellesley, Massachusetts, United States of America.
authors.forename: Karen
authors.initials: K
authors.lastname: Kemirembe
authors.forename: Kate
authors.initials: K
authors.lastname: Liebmann
authors.forename: Abigail
authors.initials: A
authors.lastname: Bootes
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Smith
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Suzuki
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004441:Ecdysterone / Q000494:pharmacology; D004703:Endocrine System; D018507:Gene Expression Regulation, Developmental; D007814:Larva / Q000502:physiology*; D018402:Manduca / Q000378:metabolism*; D008954:Models, Biological; D018978:Molting / Q000502:physiology; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology*; D013395:Sucrose / Q000494:pharmacology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D004441:Ecdysterone; D013395:Sucrose; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus