Precocious metamorphosis in the juvenile hormone-deficient mutant of the silkworm, Bombyx mori.
Precocious metamorphosis in the juvenile hormone-deficient mutant of the silkworm, Bombyx mori.
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DOI：
10.1371/journal.pgen.1002486
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发表时间：
2012
期刊：
影响因子：
4.5
通讯作者：
Shinoda T
中科院分区：
文献类型：
--
作者：
Daimon T;Kozaki T;Niwa R;Kobayashi I;Furuta K;Namiki T;Uchino K;Banno Y;Katsuma S;Tamura T;Mita K;Sezutsu H;Nakayama M;Itoyama K;Shimada T;Shinoda T
昆虫的蜕皮和变态受蜕皮激素和保幼激素（JH）两种激素的复杂控制。JH防止早熟变态，并允许幼虫经历多轮蜕皮，直到它达到变态的适当大小。在家蚕中，已经发现了几种“蜕皮”突变，这些突变表现出幼虫蜕皮数量的变化;然而，它们中没有一个被分子表征。在这里，我们报告的鉴定和表征的基因负责的二蜕皮（国防部）突变体，经历早熟变态少幼虫幼虫蜕皮。我们表明，国防部突变的结果在幼虫血淋巴中的JHS的完全丧失和突变的表型可以拯救局部应用的JH类似物。我们进行了位置克隆的mod，并发现无效突变的细胞色素P450基因CYP 15 C1的mod等位基因。我们还表明，CYP 15 C1是专门表达在咽侧体，内分泌器官，合成和分泌JHS。此外，生物化学实验表明，CYP 15 C1以高度立体特异性的方式将法呢酸环氧化为JH酸。当使用GAL 4/UAS系统在转基因mod幼虫中表达CYP 15 C1的野生型等位基因时，mod幼虫的早熟变态被拯救。因此，我们的数据表明，CYP 15 C1是负责mod突变的基因，是必不可少的JH生物合成。值得注意的是，早熟幼虫蛹转换在国防部幼虫不发生在第一或第二龄，这表明真正的环氧JH是不是必不可少的非常年轻的幼虫的B。森。我们在这个模式昆虫中鉴定出一个JH缺陷突变体，这将有助于我们更好地理解发育和变态激素控制的分子基础。昆虫的幼虫龄数在昆虫类群之间变化很大，甚至可以在种内水平上变化。然而，很少有人知道幼虫龄期的数量是如何固定在每个物种或修改的环境。蚕（Bombyx mori）为研究这个问题提供了独特的生物资源，因为有几种“蜕皮”品系在幼虫蜕皮数量上表现出差异。本研究首次定位克隆了一个蜕皮基因。我们进行了遗传和生化分析的二蜕皮（mod）突变体，这表明早熟变态少幼虫-幼虫蜕皮。我们发现，mod是一种保幼激素（JH）缺陷型突变体，无法合成JH，JH是一种防止早熟变态并允许幼虫进行多轮幼虫-幼虫蜕皮的激素。这种JH缺陷突变是迄今为止在任何昆虫物种中首次描述的，因此，mod菌株将作为一个有用的模型，用于阐明JH作用的分子机制。值得注意的是，早熟幼虫蛹转换在国防部的幼虫不发生在第一或第二龄，这表明JH的形态抑制作用是不必要的B的年轻的幼虫。森。
Insect molting and metamorphosis are intricately governed by two hormones, ecdysteroids and juvenile hormones (JHs). JHs prevent precocious metamorphosis and allow the larva to undergo multiple rounds of molting until it attains the proper size for metamorphosis. In the silkworm, Bombyx mori, several “moltinism” mutations have been identified that exhibit variations in the number of larval molts; however, none of them have been characterized molecularly. Here we report the identification and characterization of the gene responsible for the dimolting (mod) mutant that undergoes precocious metamorphosis with fewer larval–larval molts. We show that the mod mutation results in complete loss of JHs in the larval hemolymph and that the mutant phenotype can be rescued by topical application of a JH analog. We performed positional cloning of mod and found a null mutation in the cytochrome P450 gene CYP15C1 in the mod allele. We also demonstrated that CYP15C1 is specifically expressed in the corpus allatum, an endocrine organ that synthesizes and secretes JHs. Furthermore, a biochemical experiment showed that CYP15C1 epoxidizes farnesoic acid to JH acid in a highly stereospecific manner. Precocious metamorphosis of mod larvae was rescued when the wild-type allele of CYP15C1 was expressed in transgenic mod larvae using the GAL4/UAS system. Our data therefore reveal that CYP15C1 is the gene responsible for the mod mutation and is essential for JH biosynthesis. Remarkably, precocious larval–pupal transition in mod larvae does not occur in the first or second instar, suggesting that authentic epoxidized JHs are not essential in very young larvae of B. mori. Our identification of a JH–deficient mutant in this model insect will lead to a greater understanding of the molecular basis of the hormonal control of development and metamorphosis. The number of larval instars in insects varies greatly across insect taxa and can even vary at the intraspecific level. However, little is known about how the number of larval instars is fixed in each species or modified by the environment. The silkworm, Bombyx mori, provides a unique bioresource for investigating this question, as there are several “moltinism” strains that exhibit variations in the number of larval molts. The present study describes the first positional cloning of a moltinism gene. We performed genetic and biochemical analyses on the dimolting (mod) mutant, which shows precocious metamorphosis with fewer larval–larval molts. We found that mod is a juvenile hormone (JH)–deficient mutant that is unable to synthesize JH, a hormone that prevents precocious metamorphosis and allows the larvae to undergo multiple rounds of larval–larval molts. This JH–deficient mutation is the first described to date in any insect species and, therefore, the mod strain will serve as a useful model for elucidating the molecular mechanism of JH action. Remarkably, precocious larval–pupal transition in mod larvae does not occur in the first or second instar, suggesting that morphostatic action of JH is not necessary for young larvae of B. mori.
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影响因子：
3.8
作者：
Maestro, Jose L.;Pascual, Nuria;Belles, Xavier
通讯作者：
Belles, Xavier
影响因子：
2.2
作者：
KIGUCHI, K;AGUI, N
通讯作者：
AGUI, N
影响因子：
2.2
作者：
Harshman, Lawrence G.;Song, Ki-Duck;Casas, Josephina;Schuurmans, A.;Kuwano, Eichii;Kachman, Stephen D.;Riddiford, Lynn M.;Hammock, Bruce D.
通讯作者：
Hammock, Bruce D.
DOI：
10.1073/pnas.0812141106
发表时间：
2009-04-07
影响因子：
11.1
作者：
Chung, Henry;Sztal, Tamar;Daborn, Phillip J.
通讯作者：
Daborn, Phillip J.
影响因子：
3.8
作者：
Kinjoh, Terunori;Kaneko, Yu;Shinoda, Tetsuro
通讯作者：
Shinoda, Tetsuro