Hormonal regulation and developmental role of Kruppel homolog 1, a repressor of metamorphosis, in the silkworm Bombyx mori
Hormonal regulation and developmental role of Kruppel homolog 1, a repressor of metamorphosis, in the silkworm Bombyx mori
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DOI：
10.1016/j.ydbio.2014.01.022
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发表时间：
2014-04-01
影响因子：
2.7
通讯作者：
Shinoda, Tetsuro
中科院分区：
文献类型：
--
作者：
Kayukawa, Takumi;Murata, Mika;Shinoda, Tetsuro
保幼激素（JH）在昆虫幼虫发育过程中具有抑制昆虫早熟变态的作用。Kruppel同源物1（Kr-h1）是一种早期JH诱导基因，介导JH的这种作用;然而，Kr-h1的精细激素调节及其抗变质作用的分子机制尚不清楚。在这项研究中，我们试图阐明Kr-h1的激素调节和发育作用。我们发现Kr-h1在家蚕半末龄幼虫表皮中的表达是由咽侧体（CA）分泌的JH诱导的，而在预蛹期，CA不参与Kr-h1的瞬时诱导。组织培养实验表明，Kr-h1在蛹前期的瞬时峰值可能是由来自CA以外的腺体的JH和蛹前蜕皮激素的激增协同诱导的，但不能排除未知因素的参与。为了阐明Kr-h1的发育作用，我们产生了过表达Kr-h1的转基因家蚕。转基因家蚕在吐丝期之前生长正常，但在蛹前期发育受阻。在倒数第二龄去除CA的转基因家蚕没有经历早熟化蛹或幼虫-幼虫蜕皮，而是陷入蛹前停滞。这一结果表明，Kr-h1确实参与了变态的抑制，但Kr-h1单独不能实现正常的幼虫蜕皮。此外，早期蜕皮激素诱导基因（E74，E75，和广泛）在转基因家蚕的表达谱和激素反应表明，Kr-h1是不参与JH依赖的调制这些基因，这是与变态的控制。(C)2014爱思唯尔公司All rights reserved.
Juvenile hormone (JH) has an ability to repress the precocious metamorphosis of insects during their larval development. Kruppel homolog 1 (Kr-h1) is an early JH-inducible gene that mediates this action of JH; however, the fine hormonal regulation of Kr-h1 and the molecular mechanism underlying its antimetamorphic effect are little understood. In this study, we attempted to elucidate the hormonal regulation and developmental role of Kr-h1. We found that the expression of Kr-h1 in the epidermis of penultimate-instar larvae of the silkworm Bombyx mori was induced by JH secreted by the corpora allata (CA), whereas the CA were not involved in the transient induction of Kr-h1 at the prepupal stage. Tissue culture experiments suggested that the transient peak of Kr-h1 at the prepupal stage is likely to be induced cooperatively by JH derived from gland(s) other than the CA and the prepupal surge of ecdysteroid, although involvement of unknown factor(s) could not be ruled out. To elucidate the developmental role of Kr-h1, we generated transgenic silkworms overexpressing Kr-h1. The transgenic silkworms grew normally until the spinning stage, but their development was arrested at the prepupal stage. The transgenic silkworms from which the CA were removed in the penultimate instar did not undergo precocious pupation or larval-larval molt but fell into prepupal arrest. This result demonstrated that Kr-h1 is indeed involved in the repression of metamorphosis but that Kr-h1 alone is incapable of implementing normal larval molt. Moreover, the expression profiles and hormonal responses of early ecdysone-inducible genes (E74, E75, and Broad) in transgenic silkworms suggested that Kr-h1 is not involved in the JH-dependent modulation of these genes, which is associated with the control of metamorphosis. (C) 2014 Elsevier Inc. All rights reserved.