Swevers L, Drevet J R, Lunke M D, Iatrou K
Department of Medical Biochemistry, Faculty of Medicine, University of Calgary, AB, Canada.
Insect Biochem Mol Biol. 1995 Jul;25(7):857-66. doi: 10.1016/0965-1748(95)00024-p.
To understand the role that 20-hydroxy-ecdysone (20E) plays during ovarian development in Bombyx mori, we have undertaken the cloning of the silkworm ecdysone receptor (EcR) and a study of its expression during follicular cell differentiation. We have cloned a cDNA that contains a complete open reading frame for a 68.1 kDa polypeptide that shares extensive similarities with the B1 isoform of the Drosophila EcR. The presumed silkmoth EcR (BmEcR) is encoded by a single copy gene whose length is in excess of 23 kb. A portion of this gene encompassing seven exons that constitute the cloned BmEcR cDNA was also characterized. Employment of monoclonal antibodies, directed against the DNA binding domain of the Drosophila EcR, in Western blot analyses revealed the presence of a major 70 kDa polypeptide in extracts of follicular cells and other silkmoth tissues. The mRNA and protein encoded by BmEcR are present in constant amounts in follicular cells throughout vitellogenesis but disappear transiently at the onset of choriogenesis and reappear during the later stages of choriogenesis. The down-regulation of BmEcR in follicular cells during oogenesis suggest a complex relationship between 20E, the induction of the program of chorion gene expression in follicular cells during mid-vitellogenesis and the execution of this program at the end of vitellogenesis.
为了解20-羟基蜕皮酮（20E）在家蚕卵巢发育过程中所起的作用，我们进行了家蚕蜕皮激素受体（EcR）的克隆，并研究了其在滤泡细胞分化过程中的表达。我们克隆了一个cDNA，它包含一个68.1 kDa多肽的完整开放阅读框，该多肽与果蝇EcR的B1亚型有广泛的相似性。推测的家蚕EcR（BmEcR）由一个单拷贝基因编码，其长度超过23 kb。还对该基因中包含构成克隆的BmEcR cDNA的七个外显子的部分进行了表征。在蛋白质印迹分析中使用针对果蝇EcR DNA结合结构域的单克隆抗体，发现在滤泡细胞和其他家蚕组织的提取物中存在一种主要的70 kDa多肽。在整个卵黄发生过程中，滤泡细胞中由BmEcR编码的mRNA和蛋白质含量恒定，但在成卵壳开始时短暂消失，并在成卵壳后期重新出现。卵泡细胞在卵子发生过程中BmEcR的下调表明20E、卵泡细胞在卵黄发生中期绒毛膜基因表达程序的诱导以及卵黄发生末期该程序的执行之间存在复杂的关系。
