Development

The path to metamorphosis

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Science  18 Sep 2015:
Vol. 349, Issue 6254, pp. 1297
DOI: 10.1126/science.349.6254.1297-a

Larval silkworms need an extra boost on their way to metamorphosing into adult moths

PHOTO: DAVID M. PHILLIPS/SCIENCE SOURCE

The metamorphosis of a caterpillar into a moth was classically thought to be controlled largely by two hormones: one that promotes metamorphosis and one that maintains juvenile characteristics. Daimon et al. definitively tested the role of the latter, juvenile hormone, in larval silk moths. They made knockout mutants that lacked an enzyme that catalyzes juvenile hormone synthesis or lacked the two juvenile hormone receptors. Analysis of these animals showed that juvenile hormone functioned only in the late larval stages, when it restrained metamorphosis until larvae reached a sufficient size. Competence to metamorphose depended not on release from juvenile hormone inhibition but rather on the accumulation of a yet-to-be-identified signal that controlled gene expression.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1506645112 (2015).

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