Insect juvenile hormone (JH) is well known to regulate post-embryonic development and reproduction in concert with ecdysteroids in a variety of insect species. In contrast, our knowledge on the role of JH in embryonic development is limited and inconsistent. Preceding studies indicate that JH biosynthesis or JH signaling genes are dispensable in holometabolous Drosophila melanogaster and Bombyx mori, while essential in hemimetabolous Blattella germanica. In the red flour beetle Tribolium castaneum, we performed functional analyses of key factors in JH signaling, i.e. the JH receptor Methoprene-tolerant (Met) and the early JH-response gene Krüppel homolog 1 (Kr-h1) using parental RNA interference. Knockdown of Met resulted in a significant reduction in hatching rates and survival rates in the first and second larval instars. Meanwhile, knockdown of Kr-h1 caused no significant effect on hatching or survival. The unhatched embryos under Met knockdown developed up to the late embryonic stage, but their body shape was flat and tubby compared with the controls. Attempts to suppress JH biosynthesis by parental RNA interference of JH biosynthetic enzymes were unsuccessful due to insufficient knockdown efficiency. These results suggested that Met but not Kr-h1 is essential for the embryonic development of T. castaneum, although involvement of JH still remains to be examined. Taken together, the function of Met in embryonic development seems to be diverse among insect species.

中文翻译：

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耐甲氧戊丁对于红粉甲虫Tribolium castaneum的胚胎发育至关重要。

众所周知，昆虫幼体激素（JH）与蜕皮类固醇协同作用可调节胚胎后的发育和繁殖。相比之下，我们对JH在胚胎发育中的作用的认识有限且不一致。先前的研究表明，JH生物合成或JH信号基因在全果蝇果蝇和家蚕中是不可缺少的，而在半代谢德国小dis中则必不可少。在红色面粉甲虫Tribolium castaneum中，我们利用亲本RNA干扰对JH信号传导的关键因素，即JH受体甲氧戊二烯耐受（Met）和早期JH反应基因Krüppel同源1（Kr-h1）进行了功能分析。击倒Met导致第一龄和第二龄幼虫的孵化率和存活率显着降低。与此同时，敲除Kr-h1对孵化或存活没有明显影响。在Met敲除下未孵化的胚胎发育到胚胎后期，但与对照组相比，它们的体形平坦且呈大桶形。由于敲除效率不足，通过亲本RNA干扰JH生物合成酶抑制JH生物合成的尝试未成功。这些结果表明，Met而不是Kr-h1对锥栗木的胚胎发育至关重要，尽管JH的参与仍有待检查。两者合计，Met在胚胎发育中的功能似乎在昆虫物种之间是不同的。由于敲除效率不足，通过亲本RNA干扰JH生物合成酶抑制JH生物合成的尝试未成功。这些结果表明，Met而不是Kr-h1对锥栗木的胚胎发育至关重要，尽管JH的参与仍有待检查。两者合计，Met在胚胎发育中的功能似乎在昆虫物种之间是不同的。由于敲除效率不足，通过亲本RNA干扰JH生物合成酶抑制JH生物合成的尝试未成功。这些结果表明，Met而不是Kr-h1对锥栗木的胚胎发育至关重要，尽管JH的参与仍有待检查。两者合计，Met在胚胎发育中的功能似乎在昆虫物种之间是不同的。