The transcription factor c-Fos plays a negative role in prawn immunity against WSSV infection

Abstract

Members of the Fos family (c-Fos, FosB) dimerize with Jun proteins to form the activator protein 1 transcription factor complex and regulate diverse cellular processes including immunity. In the current study, a c-Fos homologue with six isoforms were identified from the oriental river prawn, Macrobrachium nipponense, and these six MnFos isoforms were produced by alternative splicing of first exon and/or exon skipping. The MnFos transcripts were detected in all tissues examined, with the highest level in the hepatopancreas. Moreover, these MnFos transcripts were significantly induced after immune stimulation by white spot syndrome virus (WSSV). Interestingly, silencing of MnFos in vivo by dsRNA interference led to a lower mortality of WSSV-infected prawns, as well as a great decrease in the expression of viral envelope protein VP28. Furthermore, silencing of MnFos induced the expression of multiple antimicrobial peptide genes in normal or WSSV-infected prawns, including crustins and anti-lipopolysaccharide factors. All these findings indicated that MnFos plays a negative role in prawn immunity against WSSV infection, possibly by its negative regulation on the expression of antimicrobial peptides. Such discovery is of great significance for further understanding of the interaction between WSSV and the immune system of prawns.