Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu Province, 212100, China.
Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture, The Sericultural Research Institute, Chinese Academy of Agricultural Sciences, Zhenjiang, Jiangsu Province, 212100, China.
Insect Sci. 2022 Feb;29(1):100-110. doi: 10.1111/1744-7917.12928. Epub 2021 May 20.
Periodic post-embryonic changes in insects, including growth, development and metamorphosis, are strictly controlled by many compounds, including steroid hormones. The biosynthesis and clearance of 20-hydroxyecdysone (20E), the major active form of the insect steroid hormone ecdysone, result in titer fluctuations that help control insect development. The inactivation of 20E in the silkworm Bombyx mori is highly tissue-specific, with CYP18A1 and ecdysone oxidase controlling 20E inactivation specifically in the mid-silk gland and midgut, respectively. Here, we characterized silkworm 3-dehydroecdysone 3α reductase (Bm3DE3α) and 3-dehydroecdysone 3β reductase (Bm3DE3β), two enzymes involved predominantly in the C-3-mediated catalysis of 20E in fat bodies. The ubiquitous and silk gland-specific overexpression of Bm3DE3α decreased the 20E titer, resulting in larval lethality and larval-pupal transition failure, respectively. In contrast, the ubiquitous and mid-silk gland-specific overexpression of Bm3DE3β increased the 20E titer, resulting in larval growth delays and lethality at the mid-fifth larval stage, respectively. Thus, Bm3DE3α and Bm3DE3β mediate fat body-specific steroid hormone metabolism in B. mori, indicating that highly diversified 20E metabolism-related mechanisms exist in different insect species.
昆虫在胚胎后期会发生周期性变化，包括生长、发育和变态等，这些变化受到许多化合物的严格控制，包括类固醇激素。20-羟蜕皮酮（20E）是昆虫蜕皮激素的主要活性形式，其生物合成和清除导致浓度波动，有助于控制昆虫发育。在桑蚕中，20E 的失活具有高度的组织特异性，CYP18A1 和蜕皮激素氧化酶分别特异性地控制中丝腺和中肠中 20E 的失活。在这里，我们对蚕 3-脱氢蜕皮酮 3α 还原酶（Bm3DE3α）和 3-脱氢蜕皮酮 3β 还原酶（Bm3DE3β）进行了表征，这两种酶主要参与脂肪体中 20E 的 C-3 介导的催化反应。Bm3DE3α 在广泛存在的组织和丝腺中的过表达降低了 20E 的浓度，导致幼虫致死和幼虫-蛹转变失败。相比之下，Bm3DE3β 在广泛存在的组织和中丝腺中的过表达增加了 20E 的浓度，导致幼虫生长延迟和在第五龄中期死亡。因此，Bm3DE3α 和 Bm3DE3β 介导了 B. mori 脂肪体中特定的类固醇激素代谢，表明不同昆虫物种中存在高度多样化的 20E 代谢相关机制。
