Hormones and growth: The control of body size and developmental growth rate in f...( ting Ras in the prothoracic gland preve...)

ting Ras in the prothoracic gland prevented ecdysone release and delayed development, creating flies that are much larger than normal. On the basis of their findings, the investigators conclude that Ras activity in the prothoracic gland regulates body size and developmental rate by regulating ecdysone release.

In the second study, Christen Mirth, James W. Truman, and Lynn M. Riddiford address how developing flies sense that they have reached the proper size to initiate a new phase of development. Their new findings show that the prothoracic gland'the organ that releases ecdysone'itself acts as a size-sensing tissue. The researchers found that by manipulating the growth of specific cells within the gland, they were able to control the timing of metamorphosis and the body size of adult flies. They showed that artificial enlargement of the prothoracic gland appeared to cause an overestimation of the larval flies' overall body size, prompting the initiation of metamorphosis before the flies surpassed the minimal viable weight necessary to survive pupation. On the basis of their findings, the authors propose that under normal conditions, growth of prothoracic gland during development helps larval flies determine when a critical body weight has been reached and when metamorphosis should be initiated.

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Contact: Heidi Hardman
hhardman@cell.com
1-617-397-2879
Cell Press
22-Sep-2005

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