BmC-LZM-like2/4 mediates antiviral defense against BmNPV via dorsal pathway

Nuclear polyhedrosis virus (NPV), a typical baculovirus, is a major pathogen infecting lepidopteran insects and serves as an eco-friendly biopesticide with high biological safety. Studying the interactions between Bombyx mori and baculovirus infection in lepidopteran models will provide valuable insights for improving pest control efficacy while mitigating economic losses in sericulture caused by pesticide overuse. Lysozyme, a widely distributed antibacterial enzyme in both vertebrates and invertebrates, functions as a classic immune effector. Although multiple lysozymes have been identified in B. mori, their specific roles in combating Bombyx mori nucleopolyhedrovirus (BmNPV) remain uncharacterized. In this study, we characterized the seven known lysozymes in B. mori and confirmed that all members exhibit conserved structural features typical of the lysozyme family. Interestingly, BmC-LZM-like4 is atypical among lysozyme genes, as it is intronless and contains an extended C-terminal sequence. Following BmNPV infection, the expression levels of BmC-LZM-like2 and BmC-LZM-like4 were significantly upregulated. Functional validation through RNA interference (RNAi) and overexpression assays demonstrated that both BmC-LZM-like2 and BmC-LZM-like4 suppress BmNPV proliferation in vitro and in vivo, suggesting their critical roles in the antiviral response. Furthermore, we investigated the potential regulatory mechanisms governing the expression of these lysozymes. Our findings indicate that the Dorsal-mediated signaling pathway may be involved in modulating the expression of BmC-LZM-like2 and BmC-LZM-like4. These data indicate that B. mori lysozyme family members BmC-LZM-like2 and BmC-LZM-like4 may be transcriptionally activated via the Dorsal-mediated signaling pathway, thereby exerting antiviral effects against baculovirus proliferation.