The morphostatic actions of juvenile hormone.
The morphostatic actions of juvenile hormone.
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DOI：
10.1016/j.ibmb.2007.05.011
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发表时间：
2007-08
影响因子：
3.8
通讯作者：
J. Truman;L. Riddiford
中科院分区：
文献类型：
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作者：
J. Truman;L. Riddiford
幼体激素（JH）在幼虫体内维持“现状”，既涉及到蜕皮过程中蜕皮激素依赖性合成的编程，也涉及到蜕皮过程中形态发生生长的抑制。后者的形态静止作用不需要体外类固醇，并已在Manduca sexta的成像盘的形成中进行了研究。前终期幼虫既有内陷盘，也有想象原基，两者都与幼虫同构生长。在最后一个阶段，年轻的椎间盘/原基开始形成成熟的椎间盘。JH抑制将未成熟的椎间盘或原基转化为完全图案的想象椎间盘的信号传导的开始和进展。这种转化通常发生在最后一个幼虫阶段快速生长的背景下，营养依赖因素似乎能够超越JH抑制。JH的形态静止作用可能对幼虫期的进化具有重要意义。对基生半代谢昆虫胚胎的研究表明，它们过早暴露于JH可以截断模式程序并导致组织早熟成熟，这是组织新幼虫形式的必要因素。这种对胚胎模式的抑制导致只要JH存在，胚胎场就保持休眠状态。一旦JH消失，为变态做准备，这些原基就可以转化为想象光盘。
The maintenance of “status quo” in larvae by juvenile hormone (JH) involves both the programming of ecdysteroid-dependent synthesis during the molt and the suppression of morphogenetic growth during the intermolt. The latter morphostatic action does not require ecdysteroids, and has been studied in the formation of imaginal discs in Manduca sexta. Preultimate larval instars have both invaginated discs and imaginal primordia, both of which grow isomorphically with the larva. In the last instar, the young discs/primordia initiate the morphogenesis and patterning that results in a mature disc. JH suppresses both the initiation and progression of the signaling that transforms immature discs or primordia into a fully patterned imaginal disc. This transformation normally occurs in the context of the rapid growth of the last larval stage, and nutrient-dependent factors appear to be able to override the JH suppression. The morphostatic action of JH may have been important for the evolution of the larval stage. Studies on embryos of basal, hemimetabolous insects show that their premature exposure to JH can truncate patterning programs and cause precocious tissue maturation, factors essential for organizing a novel larval form. This suppression of embryonic patterning then results in embryonic fields that remain dormant as long as JH is present. These are the primordia that can transform into imaginal discs once JH disappears in preparation for metamorphosis.