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Caldwell, P.E., Walkiewicz, M., Stern, M. (2005). Ras activity in the Drosophila prothoracic gland regulates body size and developmental rate via ecdysone release.  Curr. Biol. 15(20): 1785--1795.
FlyBase ID
FBrf0190001
Publication Type
Research paper
Abstract

In Drosophila, each of the three larval instars ends with a molt, triggered by release of steroid molting hormone ecdysone from the prothoracic gland (PG). Because all growth occurs during the larval stages, final body size depends on both the larval growth rate and the duration of each larval stage, which in turn might be regulated by the timing of ecdysone release.Here, we show that the expression of activated Ras, PI3 kinase (PI3K), or Raf specifically in the PG reduces body size, whereas activated Ras or PI3K, but not Raf, increases PG cell size. In contrast, expression of either dominant-negative (dn) Ras, Raf, or PI3K increases body size and prolongs the larval stages, leading to delayed pupariation, whereas expression of dn-PI3K, but not of dn-Raf or dn-Ras, reduces PG cell size. To test the possibility that altered ecdysone release is responsible for these phenotypes, we measured larval ecdysone levels indirectly, via the transcriptional activation of two ecdysone targets, E74A and E74B. We found that the activation of Ras within the PG induces precocious ecdysone release, whereas expression of either dn-PI3K or dn-Raf in the PG greatly attenuates the [ecdysone] increase that causes growth cessation and pupariation onset.We conclude that Ras activity in the PG regulates body size and the duration of each larval stage by regulating ecdysone release. We also suggest that ecdysone release is regulated in two ways: a PI3K-dependent growth-promoting effect on PG cells, and a Raf-dependent step that may involve the transcriptional regulation of ecdysone biosynthetic genes.

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Related Publication(s)
Erratum

Erratum to "Ras activity in the Drosophila prothoracic gland regulates body size and developmental rate via ecdysone release" (vol 15, pg 1785, 2005).
Caldwell et al., 2005, Curr. Biol. 15(23): 2175 [FBrf0190000]

Note

Body-size regulation: combining genetics and physiology.
Shingleton, 2005, Curr. Biol. 15(20): R825--R827 [FBrf0190044]

Flies on steroids: the interplay between ecdysone and insulin signaling.
Orme and Leevers, 2005, Cell Metab. 2(5): 277--278 [FBrf0189954]

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    Language of Publication
    English
    Additional Languages of Abstract
    Parent Publication
    Publication Type
    Journal
    Abbreviation
    Curr. Biol.
    Title
    Current Biology
    Publication Year
    1991-
    ISBN/ISSN
    0960-9822
    Data From Reference