Characterization of grass carp FosB, Fosl2, JunD transcription factors in response to GCRV infection

Activating protein-1 (AP-1) composed of Jun and Fos family proteins, which are frequently activated by pathogens to induce cellular inflammation and immune responses. In this study, by using RNA sequencing (RNA-seq) technology, we found that FosB, Fosl2, and JunD expression was co-induced 12 and 20 h in grass carp (Ctenopharyngodon idella) kidney cell line (CIK cells) after grass carp reovirus (GCRV) infection. Full-length cDNA of the three genes were cloned and phylogenetic analysis indicated that the corresponding proteins shared high homology with those in higher vertebrates. The tissue distribution analysis of the three genes showed they were ubiquitously expressed in various tissues of healthy grass carp. In infection assay, FosB, Fosl2, and JunD were up-regulated and co-expressed 8 h after GCRV infection in CIK cells. Protein interaction and co-expression network analysis revealed that FosB, Fosl2, and JunD showed similar functions and were co-expressed in mammals and fish. Taken together, these results indicated that the co-expression of the AP-1 family proteins in grass carp uniformly responds to GCRV infection. These findings provided insights into the further study of AP-1 transcription factors function during grass carp reovirus infection.