The role of 20-hydroxyecdysone and juvenile hormone in pupal commitment of the epidermis of the silkworm, Bombyx mori
The role of 20-hydroxyecdysone and juvenile hormone in pupal commitment of the epidermis of the silkworm, Bombyx mori
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DOI：
10.1016/j.mod.2008.02.001
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发表时间：
2008-05-01
影响因子：
2.6
通讯作者：
Hiruma, Kiyoshi
中科院分区：
文献类型：
--
作者：
Muramatsu, Daisuke;Kinjoh, Terunori;Hiruma, Kiyoshi
在昆虫蛹的变态过程中，蛹分化的细胞定型必须先于蛹的分化。家蚕5龄幼虫在3 ~ 6日龄表皮上的化蛹，是对蜕皮激素滴度逐渐增加的反应。然而，隐蔽的准备过程的承诺已经开始在新合成的5龄幼虫的表皮（类似于6小时前的蜕皮）作为一个感受态阶段，其中蛹的承诺在体外诱导的20-羟基蜕皮激素（20 E），但抑制JH。这种感受态阶段一直持续到25日龄，在此期间，细胞对JH和20 E的敏感性分别逐渐降低和升高。在第3天早期，离体蛹开始自主承诺，20 E刺激承诺，但JH只能部分阻止在这两种情况下的承诺。这种明显的可逆到不可逆的转变在第6天早期结束，完成蛹的承诺，当细胞完全失去了对JH的敏感性，不再表达幼虫角质层蛋白基因30。该转录因子的表达范围广，与蛹的定型密切相关，因此可以将该基因的表达作为蛹定型的分子标记。这些结果表明，暴露于20 E和损失的敏感性的表皮细胞JH蛹承诺的完成是必需的，并建议，异常长的过程超过3天可能是由于存在的可检测的JH在承诺。(c)2008爱思唯尔爱尔兰有限公司保留所有权利。
During the pupal metamorphosis in insects, cellular commitment for pupal differentiation must precede before its differentiation. The pupal commitment of Bombyx mori epidermis occurred from day 3 to day 6 last (5th) instar larvae in response to the gradual increase in ecdysteroid titer in the presence of a small amount of juvenile hormone (JH). Yet the concealed preparatory process of the commitment had begun in the newly synthesized 5th instar larval epidermis (similar to 6 h before the ecdysis) as a competence phase, in which pupal commitment in vitro was induced by 20-hydroxyecdysone (20E) but inhibited by JH. This competence phase continued until day 25th instar, and the decrease and increase in cellular sensitivity to JH and 20E, respectively, occurred gradually during this period. In early day 3, autonomous pupal commitment began in vitro and 20E stimulated the commitment, but JH could only partially prevent the commitment in both cases. This apparent reversible to irreversible transition ended in early day 6 by the completion of pupal commitment, when the cells completely lost their sensitivity to JH and no longer expressed the larval cuticle protein gene 30. The expression of the transcription factor, broad, closely followed the commitment, so that we could use this gene expression as a molecular marker for pupal commitment. These results indicate that exposure to 20E and loss of the sensitivity of the epidermal cells to JH are required for the completion of pupal commitment, and suggest that the unusually long process over 3 days could be due to the presence of the detectable JH during the commitment. (c) 2008 Elsevier Ireland Ltd. All rights reserved.