Identification of BmSP25 gene in Bombyx mori with antiviral function against BmNPV.

Bombyx mori serine protease (BmSP) is constitute a gene family of proteolytic enzymes characterized by serine residues at their active sites and play critical roles in physiological processes, including digestion, growth and development, and immune responses. As a member of the BmSP family, BmSP25 exhibits differential expression following Bombyx mori nucleopolyhedrovirus (BmNPV) infection. Our result demonstrated that BmNPV infection upregulated BmSP25 expression in both resistant (SuN) and susceptible (P50) silkworm strains, with a more pronounced response observed in SuN than in P50. To further investigate its function, siRNA-mediated knockdown of BmSP25 in BmN cells promoted the proliferation of recombinant BV-EGFP virus, whereas overexpression of BmSP25 significantly suppressed BmNPV replication. To validate its antiviral activity at the organismal level, transgenic silkworm strains overexpressing BmSP25 (BmSP25-OE) and BmSP25 knockout strains (BmSP25-KO) were generated. Following oral inoculation with BmNPV, viral proliferation was significantly inhibited in the BmSP25-OE strain, whereas viral replication was notably enhanced in the BmSP25-KO strain. This study is the first to clearly demonstrate the anti-BmNPV function of BmSP25 in silkworms, providing a foundation for further elucidation of its role in host immune defense mechanisms and identifying a potential genetic target for molecular breeding aimed at improving disease resistance in silkworms.