Characterization and functional analysis of a novel goose-type lysozyme from teleost Sebastes schlegelii with implications for antibacterial defense and immune cell modulation

Lysozymes are crucial enzymes involved in the innate immune response against bacterial pathogens. In this study, we identified and characterized a goose-type lysozyme gene (SsLyG) from the black rockfish Sebastes schlegelii, an economically important aquaculture species. The deduced amino acid sequence of SsLyG contains 495 residues, which inculded a signal peptide, an immunoglobulin domain, and a goose egg-white lysozyme (GEWL) domain. Tissue expression analysis revealed the highest SsLyG levels in blood, and its transcription was significantly upregulated in the spleen and kidney upon bacterial and polyI:C challenges. Recombinant SsLyGE (rSsLyGE) exhibited lytic activity against Micrococcus lysodeikticus and concentration-dependent binding ability to Staphylococcus aureus and Micrococcus luteus. Furthermore, rSsLyGE promoted peripheral blood lymphocyte proliferation, enhanced macrophage respiratory burst activity, and increased reactive oxygen species production. RNA interference-mediated knockdown of SsLyG resulted in higher bacterial loads in the liver and spleen after Listonella anguillarum challenge, suggesting its role in early antibacterial defense. Collectively, these findings provide insights into the immune function of SsLyG and its potential application in developing antimicrobial strategies for aquaculture.