TY - JOUR

T1 - Mechanism of threshold size assessment

T2 - Metamorphosis is triggered by the TGF-beta/Activin ligand Myoglianin

AU - He, Lorrie L.

AU - Shin, Sara H.

AU - Wang, Zhou

AU - Yuan, Isabelle

AU - Weschler, Ruthie

AU - Chiou, Allison

AU - Koyama, Takashi

AU - Nijhout, H. Frederik

AU - Suzuki, Yuichiro

PY - 2020

Y1 - 2020

N2 - 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.

AB - 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.

KW - Body size

KW - Manduca sexta

KW - Muscle growth

KW - Myoglianin

KW - Threshold size

U2 - 10.1016/j.ibmb.2020.103452

DO - 10.1016/j.ibmb.2020.103452

M3 - Journal article

C2 - 32822817

AN - SCOPUS:85090042780

VL - 126

JO - Insect Biochemistry and Molecular Biology

JF - Insect Biochemistry and Molecular Biology

SN - 0965-1748

M1 - 103452

ER -