Circular RNA identification and implication of a role of circAGO3 in the infection of white spot syndrome virus in Pacific white shrimp

Abstract

White spot syndrome is one of the most serious diseases in shrimp aquaculture. Studies and research are needed to protect shrimp from this disease. Circular RNA (circRNA) is one of RNA molecules involved in the regulations of various physiological processes. Hence, the aim of this study was to identify circRNAs in the gills of WSSV-infected shrimp using circRNA sequencing and to study its role in the condition of WSSV infection. A total of 7185 putative circRNAs were identified and only 55 differentially expressed circRNAs (DECs) were obtained. The candidate DECs were selected to determine their expressions in the gills after WSSV infection. The results showed that the expression of circAGO3 and LvAGO3 was significantly increased in WSSV-infected shrimp at 24–48 h after infection. circMAST3 and circADAP1 were significantly upregulated in WSSV-infected shrimp at 48 h after infection. To investigate the role of circAGO3 under WSSV infection, RNAi was performed. Knockdown of circAGO3 and LvAGO3 resulted in acceleration and delay of shrimp death after WSSV infection, respectively, suggesting the involvement of circAGO3 in the defense against WSSV infection in shrimp. In addition, the expression of candidate mRNAs interacting with circAGO3-miRNA was determined upon circAGO3 knockdown and WSSV infection. The result showed that all candidates including LvB4GALT7, LvSerpinB1, LvDicer, LvPIGW, and LvTret1 were down-regulated after circAGO3 knockdown and WSSV-infected shrimp, while LvIFI27L2 expression, which decreased in circAGO3 knockdown shrimp was up-regulated after WSSV infection. Our results provide information on circRNAs involved in the immune response of shrimp after WSSV infection.