Genome-wide identification and characterization of interleukin-18 gene family in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) are cold freshwater fish species belonging to the Salmonidae family, and they hold significant economic importance in the global aquaculture industry. The interleukin-18 (IL-18) gene family plays a crucial role in the immune response of rainbow trout when combating viral infections. A wide range of computational approaches were conducted to investigate the functions, phylogeny, and expressions of IL-18 family genes. The study found that there were nine IL-18 genes present on eight chromosomes of rainbow trout, and their encoded proteins were predicted to be distributed in the cytoplasm and nucleus. Genetic structures, motif and conserved domains analysis revealed that IL-18 genes in the same group have similar exons, motifs, and conserved domains. The phylogenetic study demonstrates the divergence of 38 IL-18 genes from three fish species into three distinct subgroups across time. The synteny analysis revealed the evolutionary mechanisms, such as gene duplications and mutations. In addition, the research investigated the expression of IL-18 genes in the liver tissues of rainbow trout following infection with infectious hematopoietic necrosis virus. These findings provide a comprehensive understanding of the role of IL-18 genes in O. mykiss in response to pathogenic infection.