Molecular characterization, expression, evolutionary analysis and molecular docking of the Janus activated kinase family members of largemouth bass (Micropterus salmoides).

Janus kinases (JAKs) play crucial roles in the immune responses by binding the cytokine receptors. In the present study, five JAKs family members (JAK1, JAK2a, JAK2b, JAK3, and TYK2) were identified in largemouth bass (Micropterus salmoides). The five JAKs members of largemouth bass contained several conserved protein domains, including a FERM domain, an SH2 domain, a pseudokinase (STyrkc) domain, and a tyrosine kinase (Tyrkc) domain. Phylogenetic analysis revealed the JAK2/2a/2b and JAK3 formed a clade and the JAK1/TYK2 formed another separate clade. Realtime qPCR detection showed that all five JAKs genes were constitutively expressed in ten selected tissues, with highly expression in spleen and head kidney (HK). Following Edwardsiella piscicida infection, the five JAKs genes were significantly upregulated in the spleen and primary hepatocytes at different times post infection. Further selection pressure analysis revealed the five JAKs members underwent negative selection pressures during evolution. The FERM and Tyrkc domains of the five JAK members occurred purifying selection, and involved in interaction with STAT3, which confirmed by protein-protein interaction (PPI) network and molecular docking analysis. Also, molecular docking results indicated that the hydrogens bonds and salt bonds had crucial roles in the JAK/STAT3 complexes formation. Our results indicated that JAKs had important roles in the immune response against bacterial in largemouth bass, providing basis for elucidating the mechanism of JAK/STAT signaling pathway in fish.