Ishimaru Yoshiyasu, Tomonari Sayuri, Matsuoka Yuji, Watanabe Takahito, Miyawaki Katsuyuki, Bando Tetsuya, Tomioka Kenji, Ohuchi Hideyo, Noji Sumihare, Mito Taro
Department of Life Systems, Institute of Technology and Science, Tokushima University Graduate School, Tokushima City, Tokushima, 770-8506, Japan;
Division of Chemical and Physical Analyses, Center for Technical Support, Institute of Technology and Science, Tokushima University, Tokushima City, Tokushima, 770-8506, Japan;
Proc Natl Acad Sci U S A. 2016 May 17;113(20):5634-9. doi: 10.1073/pnas.1600612113. Epub 2016 May 2.
Although butterflies undergo a dramatic morphological transformation from larva to adult via a pupal stage (holometamorphosis), crickets undergo a metamorphosis from nymph to adult without formation of a pupa (hemimetamorphosis). Despite these differences, both processes are regulated by common mechanisms that involve 20-hydroxyecdysone (20E) and juvenile hormone (JH). JH regulates many aspects of insect physiology, such as development, reproduction, diapause, and metamorphosis. Consequently, strict regulation of JH levels is crucial throughout an insect's life cycle. However, it remains unclear how JH synthesis is regulated. Here, we report that in the corpora allata of the cricket, Gryllus bimaculatus, Myoglianin (Gb'Myo), a homolog of Drosophila Myoglianin/vertebrate GDF8/11, is involved in the down-regulation of JH production by suppressing the expression of a gene encoding JH acid O-methyltransferase, Gb'jhamt In contrast, JH production is up-regulated by Decapentaplegic (Gb'Dpp) and Glass-bottom boat/60A (Gb'Gbb) signaling that occurs as part of the transcriptional activation of Gb'jhamt Gb'Myo defines the nature of each developmental transition by regulating JH titer and the interactions between JH and 20E. When Gb'myo expression is suppressed, the activation of Gb'jhamt expression and secretion of 20E induce molting, thereby leading to the next instar before the last nymphal instar. Conversely, high Gb'myo expression induces metamorphosis during the last nymphal instar through the cessation of JH synthesis. Gb'myo also regulates final insect size. Because Myo/GDF8/11 and Dpp/bone morphogenetic protein (BMP)2/4-Gbb/BMP5-8 are conserved in both invertebrates and vertebrates, the present findings provide common regulatory mechanisms for endocrine control of animal development.
尽管蝴蝶通过蛹期从幼虫到成虫经历了显著的形态转变（完全变态），但蟋蟀从若虫到成虫的变态过程中没有蛹的形成（不完全变态）。尽管存在这些差异，但这两个过程都由涉及20-羟基蜕皮激素（20E）和保幼激素（JH）的共同机制调节。JH调节昆虫生理学的许多方面，如发育、繁殖、滞育和变态。因此，在昆虫的整个生命周期中，严格调节JH水平至关重要。然而，JH合成是如何调节的仍不清楚。在这里，我们报告在双斑蟋的咽侧体中，果蝇Myoglianin/脊椎动物GDF8/11的同源物Myoglianin（Gb'Myo）通过抑制编码JH酸O-甲基转移酶的基因Gb'jhamt的表达，参与JH产生的下调。相反，JH的产生通过作为Gb'jhamt转录激活一部分的Decapentaplegic（Gb'Dpp）和Glass-bottom boat/60A（Gb'Gbb）信号传导而上调。Gb'Myo通过调节JH滴度以及JH和20E之间的相互作用来定义每个发育转变的性质。当Gb'myo表达被抑制时，Gb'jhamt表达的激活和20E的分泌诱导蜕皮，从而在最后一龄若虫之前导致下一龄若虫。相反，高Gb'myo表达通过停止JH合成在最后一龄若虫期间诱导变态。Gb'myo还调节昆虫的最终大小。由于Myo/GDF8/11和Dpp/骨形态发生蛋白（BMP）2/4 - Gbb/BMP5 - 8在无脊椎动物和脊椎动物中都是保守的，目前的研究结果为动物发育的内分泌控制提供了共同的调节机制。
