Identification, evolutionary analysis and expression patterns of the Interleukin-10 superfamily in Megalobrama amblycephala.

The interleukin-10 superfamily members (IL-10s) play a crucial role in defending against infections by pathogenic microorganisms. Meanwhile, their significance in the immune response of fish against diseases is well recognized, yet systematic analyses of the IL-10s in fish remain limited. In this study, we identified six IL-10s (Mail-10a, Mail-10b, Mail-10c, Mail-19l, Mail-22, and Mail-26) in the Megalobrama amblycephala genome. Phylogenetic analyses indicated that M. amblycephala IL-10s (MaIL-10s) were conserved in vertebrates. Meanwhile, linear analyses indicated that Mail-10a, Mail-22, and Mail-26 exhibited conserved genetic environments in representative species. In addition, syntenic analysis suggested that segmental duplication events were instrumental in the evolutionary expansion of MaIL-10s. Within the MaIL-10s, substantial variations in conserved motifs, gene structure, and protein structure were observed, indicating its complex evolutionary history. Expression profiling revealed high expression of Mail-10 analogues (Mail-10a, Mail-10b, and Mail-10c) in professional immune organs (spleen, trunk kidney, and head kidney), but low expression in the intestine. In contrast, Mail-22 showed the highest expression in mucosal tissues (intestine and gill). Mail-19l and Mail-26 exhibited the highest expression in blood. After Aeromonas hydrophila infection, MaIL-10s displayed tissue-specific and time-specific expression patterns in infected tissues (intestine, spleen, liver). In summary, our findings deepen the understanding of the IL-10 superfamily and lay the groundwork for exploring the functions of MaIL-10s in bacterial diseases.