Mechanism of threshold size assessment: Metamorphosis is triggered by the TGF-beta/Activin ligand Myoglianin.

Journal Article (Journal Article)

Although the mechanisms that control growth are now well understood, the mechanism by which animals assess their body size remains one of the great puzzles in biology. The final larval instar of holometabolous insects, after which growth stops and metamorphosis begins, is specified by a threshold size. We investigated the mechanism of threshold size assessment in the tobacco hornworm, Manduca sexta. The threshold size was found to change depending on the amount of exposure to poor nutrient conditions whereas hypoxia treatment consistently led to a lower threshold size. Under these various conditions, the mass of the muscles plus integuments was correlated with the threshold size. Furthermore, the expression of myoglianin (myo) increased at the threshold size in both M. sexta and Tribolium castaneum. Knockdown of myo in T. castaneum led to larvae that underwent supernumerary larval molts and stayed in the larval stage permanently even after passing the threshold size. We propose that increasing levels of Myo produced by the growing tissues allow larvae to assess their body size and trigger metamorphosis at the threshold size.

Full Text

Duke Authors

Cited Authors

  • He, LL; Shin, SH; Wang, Z; Yuan, I; Weschler, R; Chiou, A; Koyama, T; Nijhout, HF; Suzuki, Y

Published Date

  • November 2020

Published In

Volume / Issue

  • 126 /

Start / End Page

  • 103452 -

PubMed ID

  • 32822817

Electronic International Standard Serial Number (EISSN)

  • 1879-0240

International Standard Serial Number (ISSN)

  • 0965-1748

Digital Object Identifier (DOI)

  • 10.1016/j.ibmb.2020.103452


  • eng