Laboratory of Evolutionary and Functional Genomics, School of Life Sciences, Chongqing University, Chongqing, China.
State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China.
Mol Biol Evol. 2014 Dec;31(12):3302-13. doi: 10.1093/molbev/msu261. Epub 2014 Sep 10.
Although there are many studies to show a key role of transposable elements (TEs) in adaptive evolution of higher organisms, little is known about the molecular mechanisms. In this study, we found that a partial TE (Taguchi) inserted in the cis-regulatory region of the silkworm ecdysone oxidase (EO) gene, which encodes a crucial enzyme to reduce the titer of molting hormone (20-hydroxyecdysone, 20E). The TE insertion occurred during domestication of silkworm and the frequency of the TE insertion in the domesticated silkworm (Bombyx mori) is high, 54.24%. The linkage disequilibrium in the TE inserted strains of the domesticated silkworm was elevated. Molecular population genetics analyses suggest that this TE insertion is adaptive for the domesticated silkworm. Luminescent reporter assay shows that the TE inserted in the cis-regulatory region of the EO gene functions as a 20E-induced enhancer of the gene expression. Further, phenotypic bioassay indicates that the silkworm with the TE insertion exhibited more stable developmental phenotype than the silkworm without the TE insertion when suffering from food shortage. Thus, the inserted TE in the cis-regulatory region of the EO gene increased developmental uniformity of silkworm individuals through regulating 20E metabolism, partially explaining transformation of a domestication developmental trait in the domesticated silkworm. Our results emphasize the exceptional role of gene expression regulation in developmental transition of domesticated animals.
虽然有许多研究表明转座元件（TEs）在高等生物的适应性进化中起着关键作用，但对其分子机制知之甚少。在这项研究中，我们发现 Taguchi 是一个部分插入到家蚕蜕皮激素氧化酶（EO）基因顺式调控区的转座元件，该基因编码一种关键酶，可降低蜕皮激素（20-羟基蜕皮激素，20E）的浓度。TE 的插入发生在家蚕驯化过程中，并且在家蚕（Bombyx mori）中 TE 插入的频率很高，为 54.24%。驯化家蚕 TE 插入株系的连锁不平衡升高。分子群体遗传学分析表明，这种 TE 插入是对驯化家蚕的适应性选择。发光报告基因检测表明，插入到 EO 基因顺式调控区的 TE 作为 20E 诱导的基因表达增强子发挥作用。此外，表型生物测定表明，与没有 TE 插入的家蚕相比，TE 插入的家蚕在遭受食物短缺时表现出更稳定的发育表型。因此，插入到 EO 基因顺式调控区的 TE 通过调节 20E 代谢增加了家蚕个体的发育均匀性，部分解释了驯化家蚕发育特征的转化。我们的研究结果强调了基因表达调控在家养动物发育转变中的特殊作用。
