Alteration On The Expression Of Ayu Coagulation Factor X Gene Upon Listonella Anguillarum Infection

Coagulation factor X (FX) is a vitamin K-dependent γ-carboxylated protein of bloodcoagulation cascade. It converts prothrombin to thrombin in the presence of calcium ions andphospholipids. FX appears to play a role in inflammation via its intracellular signaling capacitiesby cleaving PAR-1and PAR-2to result in activation of the NF-κB pathway. In this study, the fulllength cDNA sequence of the ayu FX gene,1817bp in length excluding3’-polyA tail, wasdetermined for the first time. The sequence contained an open reading frame, which encoded aprotein of453amino acids with a molecular weight of50.7kDa. The predicted protein had motifstypical of animal FX, and its N-terminal24residues were the signal peptides. Sequencecomparison showed that ayu FX shared53%amino acid sequence identity with zebrafish FX. Inhealthy ayu, FX mRNA was expressed mainly in the liver and weakly in the brain and gill. AfterListonella anguillarum infection, liver FX transcriptions significantly increased, and peaked at16hpost infection. The serine protease motif of ayu FX was recombinant expressed in Escherichia coliand was subsequently used for antiserum preparation. Western blot analysis revealed that serumFX significantly increased in Listonella anguillarum infected ayu fish. In conclusion, the ayu FXgene expression was significant up-regulated in the progress of bacterial infection, suggesting FX’srole in fish immune response.