中文摘要：

Polycomb蛋白（polycomb group proteins,PcG）主要包含PRC1和PRC2 2个核心蛋白质复合体,其中PRC2在靶基因转录抑制起始阶段发挥作用,ESC作为PRC2的一个关键蛋白质,通过参与组蛋白H3K27me3的修饰来抑制基因转录。为了研究家蚕PcG蛋白的功能,克隆了长度为876 bp的家蚕Esc基因（BmEsc）WD40功能结构域编码序列,构建重组表达载体转化大肠杆菌BL21（DE3）感受态细胞后,成功表达并纯化了目的蛋白质,可用于进一步的抗体制备和功能研究。利用实时荧光定量PCR检测BmEsc基因在家蚕不同发育时期的表达特征：非滞育卵中该基因的表达水平在卵期1~5 d相对较高,而滞育卵中该基因在卵期1~2 d的表达量低于非滞育卵,卵期6~9 d的表达量却高于非滞育卵,并保持较稳定水平;该基因在各龄幼虫龄中期的表达量较低,在5龄1~3 d和化蛹前的一段时期表达量较高,在蛹期的表达水平变化不大。初步推测BmEsc可能在家蚕早期胚胎发育、滞育卵中的靶基因沉默以及在幼虫蜕皮前后和化蛹变态前的组织分化过程中发挥重要作用。

英文摘要：

Polycomb group proteins（ PcG） mainly include two core protein complexes PRC1 and PRC2. PRC2 plays roles at the initiation stage of transcriptional inhibition. As the key protein of PRC2,ESC is involved in gene silencing by trimethylation of H3K27me3. In order to study the function of PcG proteins in silkworm（ Bombyx mori）,an 876 bp sequence encoding WD40 domain of BmEsc gene was cloned. The recombinant expression vector was constructed and then transformed into competent cells of Escherichia coli BL21（ DE3）. The target protein was successfully expressed and purified,which was used for antibody preparation and functional study. Quantitative real-time PCR was applied to detect the expression pattern of BmEsc gene at different developmental stages of silkworm. It was found that in non-diapauseeggs,BmEsc was highly expressed on day 1 to day 5 at egg stage. In diapause eggs,the expression level of BmEsc on day 1 to day 2 at egg stage was lower than that in non-diapause eggs,but the expression of BmEsc on day 6 to day 9 at egg stage was much higher than that in non-diapause eggs and maintained at a stable level. Its expression level was low in middle of each instar,while it was expressed highly on day 1 to day 3 of the 5th instar and before pupation. The expression level of BmEsc had little change during the pupal stage. It is preliminarilyspeculated that BmEsc may play important roles in early embryogenesis,target gene silencing in diapause eggs and tissue differentiation before and after molting of the larvae and before pupation.