Oxidative stress plays a key role in the regulation and control of cell survival.Reactive oxygen species (ROS) contribute to apoptosis in mammalian cells by mediating oxidative stress.We previously identified apoptosis-related genes in the lepidopteran model,the silkworm Bombyx mori.The aim of this study was to determine whether the mitochondrial apoptotic pathway was induced by ROS-mediated oxidative stress in BmN-SWU1,an ovarian cell line of Bombyx mori.We found that BmN-SWU1 cells exhibited apoptotic morphology after exposure to H2O2,characterized by cell protuberances,cytoplasmic condensation and apoptotic bodies.During H2O2-induced apoptosis,BmN-SWU1 cells displayed changes in mitochondrial distribution,loss of mitochondrial membrane potential,a marked increase of intracellular ROS and Ca2+ levels,release of cytochrome c from mitochondria.We also provide further evidence that the expression levels of pro-apoptotic genes,such as Bmapaf-1,BmDronc,BmICE,BmEndoG,BmP53,were marked increased as well as cytochrome c,p53 the death receptor gene BmDredd and the activity of caspase-9 and caspase-3.Concurrently,we observed a notable decrease of anti-apoptotic Bcl-2,Bcl-2 homologous gene BmBuffy and caspase inhibitor gene BmIAP.These results demonstrated that the mitochondrial apoptotic pathway in BmN-SWU1 cells was induced by H2O2.