Non-molting glossy/shroud encodes a short-chain dehydrogenase/reductase that functions in the 'Black Box' of the ecdysteroid biosynthesis pathway
Non-molting glossy/shroud encodes a short-chain dehydrogenase/reductase that functions in the 'Black Box' of the ecdysteroid biosynthesis pathway
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DOI：
10.1242/dev.045641
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发表时间：
2010-06-15
期刊：
影响因子：
4.6
通讯作者：
Shinoda, Tetsuro
中科院分区：
文献类型：
--
作者：
Niwa, Ryusuke;Namiki, Toshiki;Shinoda, Tetsuro
在昆虫中，蜕皮和变态的精确时间是由主要的类固醇激素蜕皮激素严格指导的。在从膳食胆固醇合成蜕皮激素的多个转化步骤中，7-脱氢胆固醇向5 β-酮二醇的转化，即所谓的“黑匣子”，被认为是重要的限速步骤。虽然一些蜕皮激素合成所必需的基因最近已经被发现，但对黑匣子功能至关重要的基因知之甚少。在这里，我们报告了一种新型的蜕皮类固醇基因，非蜕皮光泽（nm-g）/shroud（sro），它编码短链脱氢酶/还原酶。该基因首先是通过定位克隆家蚕nm-g突变体而分离的，该突变体表现出低蜕皮激素滴度并因此导致幼虫停滞表型。在果蝇（Drosophila melanogaster）中，与nm-g最接近的基因由sro基因座编码，sro基因座是以胚胎蜕皮激素缺乏为特征的万圣节突变成员之一。sro突变体的致死性被sro或nm-g基因的过表达所挽救，表明这两个基因是直向的。nm-g和sro基因主要在产生蜕皮激素的组织中表达，例如前胸腺和卵巢。此外，由这些基因的功能丧失引起的表型通过应用蜕皮类固醇及其前体5 β-酮二醇而恢复，但不能通过胆固醇或7-脱氢胆固醇恢复。总之，我们得出结论，Nm-g/Sro家族蛋白是一个必不可少的酶蜕皮甾体生成的黑箱工作。
In insects, the precise timing of molting and metamorphosis is strictly guided by a principal steroid hormone, ecdysone. Among the multiple conversion steps for synthesizing ecdysone from dietary cholesterol, the conversion of 7-dehydrocholesterol to 5 beta-ketodiol, the so-called 'Black Box', is thought to be the important rate-limiting step. Although a number of genes essential for ecdysone synthesis have recently been revealed, much less is known about the genes that are crucial for functioning in the Black Box. Here we report on a novel ecdysteroidgenic gene, non-molting glossy (nm-g)/shroud (sro), which encodes a short-chain dehydrogenase/reductase. This gene was first isolated by positional cloning of the nm-g mutant of the silkworm Bombyx mori, which exhibits a low ecdysteroid titer and consequently causes a larval arrest phenotype. In the fruit fly, Drosophila melanogaster, the closest gene to nm-g is encoded by the sro locus, one of the Halloween mutant members that are characterized by embryonic ecdysone deficiency. The lethality of the sro mutant is rescued by the overexpression of either sro or nm-g genes, indicating that these two genes are orthologous. Both the nm-g and the sro genes are predominantly expressed in tissues producing ecdysone, such as the prothoracic glands and the ovaries. Furthermore, the phenotypes caused by the loss of function of these genes are restored by the application of ecdysteroids and their precursor 5 beta-ketodiol, but not by cholesterol or 7-dehydrocholesterol. Altogether, we conclude that the Nm-g/Sro family protein is an essential enzyme for ecdysteroidogenesis working in the Black Box.