Role of Marsupenaeus japonicus crustin-like peptide against Vibrio penaeicida and white spot syndrome virus infection

• MjCRS is highly expressed in hemocytes and can be silenced by double-stranded RNA.
• Silencing of MjCRS makes the shrimp susceptible to bacterial but not viral infection.
• Expression profiles indicate its importance in combatting bacterial infection.
• MjCRS is not involved in controlling viral replication.
• dsRNA treatment and microbial infection decreased the total hemocyte counts.

Crustins are important AMP that has been identified in crustaceans. In this study, the role of Marsupenaeus japonicus crustin-like peptide (MjCRS) was examined in vivo by RNA interference (RNAi) using double-stranded RNA (dsRNA). Tissue expression analysis revealed that MjCRS transcripts are expressed in different tissues tested with the highest expression observed in hemocytes. Treatment with double-stranded RNA specific to MjCRS led to a significant reduction of MjCRS transcripts within the hemocytes. When MjCRS was silenced and subsequently infected with Vibrio penaeicida final mortality was significantly higher compared with PBS and dsGFP treated groups. On the other hand, final mortalities of MjCRS silenced and PBS injected groups were not significantly different after infection with white spot virus, however, both are significantly higher compared with dsGFP treated group. V. penaeicida infection significantly decreased MjCRS expression at 3, 6, 12 and 24 h followed by significant increase at 48 h post-infection. On the contrary, white spot infection significantly increased MjCRS expression at 6 and 12 h and decreased at 48 h post-infection. dsRNA treatment alone decreased total hemocyte counts (THCs) and subsequent V. penaeicida or white spot virus infection further decreased THCs. VP28 gene expression was both similarly increased in PBS injected group and MjCRS silenced group at 24 and 48 h-post infection. Results suggest that MjCRS is involved in antibacterial defense and might not have critical function against viral infection.