Golden pompano, Trachinotus ovatus, is a perciform fish with great economic value and is widely cultured in the coastal areas of China. The wide occurrence of bacterial, parasitic and viral diseases has seriously threatened the sustainable development of the golden pompano culture industry. Janus kinases (JAKs) play important roles in most cytokine-mediated inflammatory responses, antiviral immune responses, autoimmune responses and disease pathologies. The present study aimed to obtain the full-length cDNA sequences of JAKs (JAK1, JAK2a, JAK3 and TYK2) from golden pompano and investigate their roles following stimulation with lipopolysaccharide (LPS), polyriboinosinic-polyribocytidylic acid (poly I:C) and Vibrio alginolyticus using RT-PCR, RACE-PCR and real-time qPCR methods. All four JAK proteins of golden pompano shared similar conserved domains, had high identities and clustered well with their teleost counterparts in phylogenetic analysis. Furthermore, these four genes were expressed in all examined tissues from healthy fish and induced in head kidney (HK), spleen, liver and gill post LPS, poly I:C and V. alginolyticus stimulation. Knowledge of the roles of JAKs in the immune response to different microbial pathogens provides a basis for further understanding of these functions.

High-throughput sequencing has significantly advanced the exploration of fish immune mechanisms, enabling a more detailed understanding of immune responses and their underlying molecular pathways. In this study, we applied comparative transcriptomics and single-cell RNA sequencing to investigate the immune mechanisms of tilapia in response to different pathogenic bacteria. Our results demonstrated that nonspecific cytotoxic cells (NCCs) and monocytes/macrophages (Mos/Mφs) mounted the most pronounced responses to both Streptococcus agalactiae and Aeromonas hydrophila infections. Moreover, Mos/Mφs exhibited distinct differentiation patterns depending on the bacterial challenge. Collectively, these findings offer new insights into the antibacterial immune strategies of lower vertebrates.