FIGURE 1.

Schematic of the experimental generation of the pol I-driven SFTSV minigenome system and the cDNA-derived virus-like RNA synthesis system. (A) Organization of murine pol I-driven SFTSV L, M, and S minigenome systems. The minigenome system consists of the minigenome plasmid and the expression plasmids of RdRp and N. Briefly, ORF of SFTSV RdRp or N was respectively, inserted into vector pCAGGSP7 by double digestion (KpnI and NotI); Firefly luciferase (FLuc) gene flanked by the 5′ and 3′ UTR of L/M/S was inserted into the pRF42 in antigenome (+) orientation. (B) Transcription and replication in the cDNA-derived virus-like RNA synthesis system of SFTSV. Virus-like vRNAs and cRNAs were respectively, transcribed by pRF42-SV-L/M/SUTR-FLuc (–) and pRF42-SV-L/M/SUTR-FLuc (+) based on murine pol I promoter. Meanwhile, cRNAs can be synthesized by replication using vRNAs as template and subsequently can be used as templates to synthesize vRNA by transcription. The vRNA can also be used as templates to synthesize mRNA through transcription. The 5′ capped mRNA can encode the reporter protein (FLuc or EGFP), which can be used as an indicator for viral RNA synthesis.