Involvement of the transcription factor E75 in adult cuticular formation in the red flour beetle Tribolium castaneum
Involvement of the transcription factor E75 in adult cuticular formation in the red flour beetle Tribolium castaneum
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DOI：
10.1016/j.ibmb.2020.103450
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发表时间：
2020-11-01
影响因子：
3.8
通讯作者：
Minakuchi, Chieka
中科院分区：
文献类型：
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作者：
Sapin, Gelyn D.;Tomoda, Kai;Minakuchi, Chieka
昆虫的成虫变态过程中通常伴随着检测不到的保幼激素（JH）水平。赤拟谷盗Tribolium castaneum在成虫发育过程中，发生成虫角质层的生物合成，随后发生其色素沉着和硬化，并且在pharate成虫中角质层的深色变得可见。在这里，我们更详细地研究了成体表皮形成的分子机制。我们注意到，外源性JH模拟物（JHM）处理第0天的脓疱没有抑制色素沉着或巩膜化，而是提前两天诱导成人角质层早熟色素沉着。定量RT-PCR分析显示，蜕皮激素诱导的蛋白75 B（E75）在JHM处理的脓疱下调。同时，酪氨酸羟化酶（Th），参与角质色素沉着和硬化的酶，早熟诱导，而结构角质蛋白CPR 27下调，外源JHM治疗。RNA干扰介导的E75敲低导致早熟的成人表皮色素沉着，这类似于JHM治疗引起的表型。值得注意的是，在E75敲低的情况下观察到Th的上调以及CPR 27的抑制。同时，JHM处理抑制了参与黑色素合成的基因的表达，如Yellow-y和漆酶2，但E75敲除并没有导致其表达的显著降低。总而言之，这些结果为成人表皮形成的调节机制提供了见解;参与成人表皮形成的基因的转录在适当的时机进行，并且检测不到JH，而外源性JHM处理会扰乱它们的转录。对于其中一些基因如Th和CPR 27，E75参与转录调控。本研究揭示了JHM作为杀虫剂的分子作用模式;外源JHM处理干扰了参与成虫表皮形成的基因的表达，从而导致作为pharate成虫的致死性。
Insect adult metamorphosis generally proceeds with undetectable levels of juvenile hormone (JH). In adult development of the red flour beetle Tribolium castaneum, biosynthesis of adult cuticle followed by its pigmentation and sclerotization occurs, and dark coloration of the cuticle becomes visible in pharate adults. Here, we examined the molecular mechanism of adult cuticular formation in more detail. We noticed that an exogenous JH mimic (JHM) treatment of Day 0 pupae did not inhibit pigmentation or sclemtization, but instead, induced precocious pigmentation of adult cuticle two days in advance. Quantitative RT-PCR analyses revealed that ecdysone-induced protein 75B (E75) is downregulated in JHM-treated pupae. Meanwhile, tyrosine hydroxylase (Th), an enzyme involved in cuticular pigmentation and sclerotization, was precociously induced, whereas a structural cuticular protein CPR27 was downregulated, by exogenous JHM treatment. RNA interference-mediated knockdown of E75 resulted in precocious adult cuticular pigmentation, which resembled the phenotype caused by JHM treatment. Notably, upregulation of Th as well as suppression of CPR27 were observed with E75 knockdown. Meanwhile, JHM treatment suppressed the expression of genes involved in melanin synthesis, such as Yellow-y and Laccase 2, but E75 knockdown did not result in marked reduction in their expression. Taken together, these results provided insights into the regulatory mechanisms of adult cuticular formation; the transcription of genes involved in adult cuticular formation proceeds in a proper timing with undetectable JH, and exogenous JHM treatment disturbs their transcription. For some of these genes such as Th and CPR27, E75 is involved in transcriptional regulation. This study shed light on the molecular mode of action of JHM as insecticides; exogenous JHM treatment disturbed the expression of genes involved in the adult cuticular formation, which resulted in lethality as pharate adults.