@article {6383,
	title = {A molt timer is involved in the metamorphic molt in Manduca sexta larvae.},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {110},
	year = {2013},
	month = {2013 Jul 30},
	pages = {12518-25},
	abstract = {<p>Manduca sexta larvae are a model for growth control in insects, particularly for the demonstration of critical weight, a threshold weight that the larva must surpass before it can enter metamorphosis on a normal schedule, and the inhibitory action of juvenile hormone on this checkpoint. We examined the effects of nutrition on allatectomized (CAX) larvae that lack juvenile hormone to impose the critical weight checkpoint. Normal larvae respond to prolonged starvation at the start of the last larval stage, by extending their subsequent feeding period to ensure that they begin metamorphosis above critical weight. CAX larvae, by contrast, show no homeostatic adjustment to starvation but start metamorphosis 4 d after feeding onset, regardless of larval size or the state of development of their imaginal discs. By feeding starved CAX larvae for various durations, we found that feeding for only 12-24 h was sufficient to result in metamorphosis on day 4, regardless of further feeding or body size. Manipulation of diet composition showed that protein was the critical macronutrient to initiate this timing. This constant period between the start of feeding and the onset of metamorphosis suggests that larvae possess a molt timer that establishes a minimal time to metamorphosis. Ligation experiments indicate that a portion of the timing may occur in the prothoracic glands. This positive system that promotes molting and the negative control via the critical weight checkpoint provide antagonistic pathways that evolution can modify to adapt growth to the ecological needs of different insects.</p>
},
	issn = {1091-6490},
	doi = {10.1073/pnas.1311405110},
	author = {Suzuki, Yuichiro and Koyama, Takashi and Hiruma, Kiyoshi and Riddiford, Lynn M and Truman, James W}
}
@article {2503,
	title = {Insulin/IGF signaling regulates the change in commitment in imaginal discs and primordia by overriding the effect of juvenile hormone.},
	journal = {Developmental Biology},
	volume = {324},
	year = {2008},
	month = {2008 Dec 15},
	pages = {258-65},
	abstract = {<p>At the beginning of the final larval (fifth) instar of Manduca sexta, imaginal precursors including wing discs and eye primordia initiate metamorphic changes, such as pupal commitment, patterning and cell proliferation. Juvenile hormone (JH) prevents these changes in earlier instars and in starved final instar larvae, but nutrient intake overcomes this effect of JH in the latter. In this study, we show that a molecular marker of pupal commitment, broad, is up-regulated in the wing discs by feeding on sucrose or by bovine insulin or Manduca bombyxin in starved final instar larvae. This effect of insulin could not be prevented by JH. In vitro insulin had no effect on broad expression but relieved the suppression of broad expression by JH. This effect of insulin was directly on the disc as shown by its reduction in the presence of insulin receptor dsRNA. In starved penultimate fourth instar larvae, broad expression in the wing disc was not up-regulated by insulin. The discs became responsive to this action of insulin during the molt to the fifth instar together with the ability to become pupally committed in response to 20-hydroxyecdysone. Thus, the Manduca bombyxin acts as a metamorphosis-initiating factor in the imaginal precursors.</p>
},
	keywords = {Animals, Cells, Cloning, Cultured, Developmental, Ecdysterone, Gene Expression Regulation, Insect Proteins, Insulin, Juvenile Hormones, Larva, Manduca, Messenger, Molecular, Receptor, RNA, RNA Interference, Signal Transduction, Somatomedins, Sucrose, Wing},
	issn = {1095-564X},
	doi = {10.1016/j.ydbio.2008.09.017},
	author = {Koyama, Takashi and Syropyatova, Maria O and Riddiford, Lynn M}
}
