| Summary: | Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the primary pathogens of the silkworm. <i>Cytochrome c</i> (<i>cytc</i>) showed a significant response to BmNPV infection in our previous transcriptome study. However, little is known about the role of <i>Bombyx mori</i> cytc (Bmcytc) in resistance to BmNPV infection. In this study, the expression levels analysis of <i>Bmcytc</i> showed stable expression levels in selected tissues of the resistant strain AN following BmNPV infection, while there was downregulation in the susceptible strain p50, except in the malpighian tubule. To further study the role of <i>Bmcytc</i> in viral infection, <i>Bmcytc</i> was knocked down with siRNA in vitro, resulting in significant downregulation of selected downstream genes of the mitochondrial pathway, including <i>Bmapaf</i>, <i>Bmcaspase-Nc</i>, and <i>Bmcaspase-1</i>; this was also confirmed by overexpression of <i>Bmcytc</i> using the pIZT/V5-His-mCherry insect vector, except <i>Bmcaspase-1</i>. Moreover, knockdown of <i>Bmcytc</i> significantly promoted the infection process of BmNPV in vitro, while the infection was inhibited by overexpression of <i>Bmcytc</i> at the early stage and subsequently increased rapidly. Based on these results, we concluded that <i>Bmcytc</i> plays a vital role in BmNPV infection by regulating the mitochondrial apoptosis pathway. Our work provides valuable data for the clarification of the mechanism of silkworm resistance to BmNPV infection.
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