Objective Function of peroxiredoxin 6 gene (prx 6) in the antimicrobial innate immune response mechanism of Procambarus clarkii against Edwardsiella ictaluri was studied.
Methods To confirm the involvement of prx 6 in the immunological response, gene expressions in the haemocytes, hepatopancreas, gills, and intestines of the P. clarkii were examined. Double-strand RNA (dsRNA) of the antimicrobial peptide (Amp) gene in P. clarkii, prx 6, was prepared by in vitro transcription in crayfish blood sinusoids using sterile syringes with the effect verified by qRT-PCR analysis. In a challenge test, survival rate of the E. ictaluri-inoculated crayfish was determined by a RNAi assay with the changes in prx 6 expression analyzed by qRT-PCR.
Results The upregulated expressions of prx 6 in various crayfish tissues after the E.ictaluri stimulation indicated a positive association of the gene with the pathogenic invasion. Furthermore, an injection of the in vitro prepared dsRNA significantly suppressed the expression of prx 6 in the hepatopancreas confirming the response of the crayfish. The RNAi assay also showed a significant lower survival rate of the crayfish in the E. ictalurid-inoculation group than that in the dsGFP control indicating a significant effect of prx 6 in combating the bacterial infections. Additionally, in the challenge test some other endogenous Amp genes, such as ALF 4, ALF 1, crustin 1, crustin 2, lys, and lectin 2, were significantly downregulated in the E. ictaluri-inoculated crayfish in comparison with the dsGFP-inoculated counterparts. It was speculated that prx 6 contributed to the crayfish resistance to the infection by E. ictaluri through modulating Amp genes resulting in an improved survival. It was hypothesized that prx 6 participated in the innate immune response of crayfish against E. ictaluri through regulations on the endogenous Amp genes.