DNA methylation at the fifth position of cytosine (5-methylcytosine, 5mC) is a crucial epigenetic modification for regulating gene expression, but little is known about how it regulates gene expression in insects. Here, we pursue the detailed molecular mechanism by which DNMT1-mediated 5mC maintenance regulates female reproduction in the German cockroach, Blattella germanica. Our results show that Dnmt1 knockdown decreases the level of 5mC in the ovary, upregulating numerous genes during choriogenesis, especially the transcription factor ftz-f1. The hypomethylation at the ftz-f1 promoter region increases and prolongs ftz-f1 expression in ovarian follicle cells during choriogenesis, which consequently causes aberrantly high levels of 20-hydroxyecdysone and excessively upregulates the extracellular matrix remodeling gene Mmp1. These changes further impair choriogenesis and disrupt fertilization by causing anoikis of the follicle cells, a shortage of chorion proteins, and malformation of the sponge-like bodies. This study significantly advances our understanding of how DNA 5mC modification regulates female reproduction in insects.

胞嘧啶第五位的 DNA 甲基化（5-甲基胞嘧啶，5mC）是调节基因表达的关键表观遗传修饰，但人们对其如何调节昆虫基因表达知之甚少。在这里，我们探究 DNMT1 介导的 5mC 维持调节德国小蠊 ( Blattella germanica)雌性繁殖的详细分子机制。我们的结果表明， Dnmt1敲除降低了卵巢中 5mC 的水平，上调了绒毛膜形成过程中的许多基因，尤其是转录因子ftz-f1 。 ftz-f1启动子区域的低甲基化会增加并延长绒毛膜形成过程中卵巢卵泡细胞中ftz-f1 的表达，从而导致异常高水平的 20-羟基蜕皮激素并过度上调细胞外基质重塑基因Mmp1 。这些变化会导致卵泡细胞失巢、绒毛膜蛋白缺乏和海绵状体畸形，从而进一步损害绒毛膜发生并破坏受精。这项研究显着增进了我们对 DNA 5mC 修饰如何调节昆虫雌性繁殖的理解。