Discovery and Characterization of the Gene in Atlantic Salmon: Evolutionary Implications, Structural Functions, and Innate Immune Responses to and Infections.

The innate immune response in , mediated by pattern recognition receptors (PRRs), is crucial for defending against pathogens. This study examined DDX41 protein functions as a cytosolic/nuclear sensor for cyclic dinucleotides, RNA, and DNA from invasive intracellular bacteria. The investigation determined the existence, conservation, and functional expression of the gene in . In silico predictions and experimental validations identified a single gene on chromosome 5 in , showing 83.92% homology with its human counterpart. Transcriptomic analysis in salmon head kidney confirmed gene transcriptional integrity. Proteomic identification through mass spectrometry characterized three unique peptides with 99.99% statistical confidence. Phylogenetic analysis demonstrated significant evolutionary conservation across species. Functional gene expression analysis in SHK-1 cells infected by and indicated significant upregulation of DDX41, correlated with increased proinflammatory cytokine levels and activation of and interferon signaling pathways. In vivo studies corroborated DDX41 activation in immune responses, particularly when was challenged with , underscoring its potential in enhancing disease resistance. This is the first study to identify the DDX41 pathway as a key component in innate immune response to invading pathogens, establishing a basis for future research in salmonid disease resistance.