Transcriptomic analysis of the comprehensive immune responses induced by recombinant interferon γ and characterization of antiviral Mx2 protein in black rockfish Sebastes schlegelii

Interferon-gamma (IFNγ) is a key immune regulator in teleost fish, yet its mechanisms of action remain poorly understood. In this study, we investigated the immunomodulatory role of recombinant Sebastes schlegelii IFNγ (rSsIFNγ) in intestinal cells (SSICs) and characterized the antiviral effector myxovirus resistance protein 2 (SsMx2). Transcriptome sequencing revealed 7231 differentially expressed genes, with principal component analysis (PCA) showing clear separation between experimental and control groups. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated significant enrichment of immune-related pathways, particularly antigen processing and presentation, Janus kinase–signal transducer and activator of transcription (JAK-STAT), and tumor necrosis factor (TNF) signaling. rSsIFNγ treatment upregulated major histocompatibility complex (MHC) molecules, key cytokines, and multiple antimicrobial effectors. We cloned the full-length ssmx2 cDNA, which encodes a 644-amino acid protein containing conserved GTPase and effector domains. Phylogenetic analysis confirmed high sequence conservation with other teleost Mx proteins. ssmx2 showed tissue-specific expression, was strongly induced by pathogen challenge and rSsIFNγ stimulation, and localized mainly to the cytoplasm. Collectively, these results demonstrate that rSsIFNγ reprograms intestinal immune responses through activation of multiple signaling pathways and identify SsMx2 as an important interferon-inducible antiviral effector in rockfish.