Molecular characterization and expression analysis of tiger puffer (Takifugu rubripes) interferon regulatory factor in response to Vibrio harveyi infection.

The interferon regulatory factor (IRF) family serves as pivotal transcriptional regulators that mediate the initiation of host innate immune responses to pathogen invasion by modulating the transcriptional expression of interferon genes, which in turn induces the expression of downstream immune-related genes. However, studies on the IRF gene family in tiger puffer (Takifugu rubripes) remain limited, particularly concerning its functional role in mediating anti-Vibrio immune responses. In this study, a total of 12 TrIRF genes were identified in the genome of tiger puffer, distributed across 11 chromosomes. Phylogenetic analysis classified these TrIRF genes into four distinct subfamilies: IRF1, IRF3, IRF4, and IRF5. Domain prediction indicated that the IRF1 subfamily possesses only the IRF domain, whereas the other subfamilies additionally contain the IRF-3 domain. Expression profiling demonstrated distinct tissue-specific patterns of the 12 TrIRFs in healthy tiger puffer, with most genes exhibiting higher expression levels in immune-related tissues such as the head kidney, gill, intestine, and spleen, and further revealed their differential expression patterns during larval development. Furthermore, following Vibrio harveyi infection, significant differential expression of TrIRFs was observed in the intestine, spleen, and liver, with an overall trend of initial upregulation followed by subsequent downregulation over time. These findings provide significant reference data for investigating IRF functions in teleosts and contribute to the understanding of innate immunity in vertebrates.