Suppression of argonautes compromises viral infection in Penaeus monodon

Argonaute (Ago) proteins, the catalytic component of an RNA-induced silencing complex (RISC) in RNA interference pathway, function in diverse processes, especially in antiviral defense and transposon regulation. So far, cDNAs encoding four members of Argonaute were found in Penaeus monodon (PmAgo1-4). Two PmAgo proteins, PmAgo1 and PmAgo3 shared high percentage of amino acid identity to Ago1 and Ago2, respectively in other Penaeid shrimps. Therefore, the possible roles of PmAgo1 and PmAgo3 upon viral infection in shrimp were characterized in this study. The level of PmAgo1 mRNA expression in shrimp hemolymph was stimulated upon YHV challenge, but not with dsRNA administration. Interestingly, silencing of either PmAgo1 or PmAgo3 using sequence-specific dsRNAs impaired the efficiency of PmRab7-dsRNA to knockdown shrimp endogenous PmRab7 expression. Inhibition of yellow head virus (YHV) replication and delayed mortality rate were also observed in both PmAgo1-and PmAgo3-knockdown shrimp. In addition, silencing of PmAgo3 transcript, but not PmAgo1, revealed partial inhibition of white spot syndrome virus (WSSV) infection and delayed mortality rate. Therefore, our study provides insights into PmAgo1and PmAgo3 functions that are involved in a dsRNA-mediated gene silencing pathway and play roles in YHV and WSSV replication in the shrimp.