Expression analysis of proteins and genes related to phagosome-lysosome and immunohistochemical features of Cynoglossus semilaevis upon Vibrio vulnificus infection

The phagosome-lysosome (PL) signaling pathway plays an important role in the immune system of fish. However, the molecular mechanism underlying PL signaling in fish against Vibrio vulnificus infection remains still unclear. In this study, the half-smooth tongue sole (Cynoglossus semilaevis) infected with V. vulnificus strain ST-6 was used as an experiment model, the immunohistochemical features were evaluated, and spatiotemporal expression analysis of genes and proteins related to PL pathway was verified, respectively. The results showed that the positive staining was observed in the various tissues such as liver, intestine, kidney, spleen, and gills of the infected fish. The differential expressions of PL-related proteins were screened and identified by iTRAQ analysis, and their gene expressions were determined by qRT-PCR detection. The spatiotemporal expression patters were confirmed and most of PL-related genes tended to be downregulated during the early infection at 12 and 36 h post-infection (hpi). Moreover, the protein-protein interaction (PPI) analysis was described for PL pathway. This is the first report on the PL response of C. semilaevis to V. vulnificus infection, which will provide a scientific reference for further elucidating the molecular mechanism of the phagosome-lysosome in marine fish.