Project description:Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne bunyavirus that causes severe clinical symptoms and mortality in humans. Haemaphysalis longicornis tick has been identified as the competent vector for SFTSV transmission. Although antiviral RNA interference (RNAi) in insects has been well documented, the degree to which RNAi contributes to antiviral defense in ticks is still largely elusive. In this study, utilizing arthropod-borne RNA viruses, including SFTSV, we find abundant virus-derived small interfering RNAs (vsiRNAs) are induced in H. longicornis after infection through either microinjection or natural blood-feeding. Furthermore, we identify a Dicer2-like homolog, the core protein of antiviral RNAi pathway, in H. longicornis and knocking down this gene exacerbated virus amplification. To counteract this antiviral RNAi of ticks, viruses have evolved suppressors of RNAi (VSRs). Here, we show that reduced viral replication inversely correlated with the accumulation of vsiRNAs in ticks after infection with recombinant sindbis virus (SINV) expressing heterologous VSR proteins. Elucidating the antiviral RNAi pathway of ticks by model arthropod-borne RNA viruses in vivo is critical to understanding the virus-host interaction, providing a feasible intervention strategy to control tick-borne arbovirus transmission.
Project description:Analyses of new genomic, transcriptomic or proteomic data commonly result in trashing many unidentified data escaping the ‘canonical’ DNA-RNA-protein scheme. Testing systematic exchanges of nucleotides over long stretches produces inversed RNA pieces (here named “swinger” RNA) differing from their template DNA. These may explain some trashed data. Here analyses of genomic, transcriptomic and proteomic data of the pathogenic Tropheryma whipplei according to canonical genomic, transcriptomic and translational 'rules' resulted in trashing 58.9% of DNA, 37.7% RNA and about 85% of mass spectra (corresponding to peptides). In the trash, we found numerous DNA/RNA fragments compatible with “swinger” polymerization. Genomic sequences covered by «swinger» DNA and RNA are 3X more frequent than expected by chance and explained 12.4 and 20.8% of the rejected DNA and RNA sequences, respectively. As for peptides, several match with “swinger” RNAs, including some chimera, translated from both regular, and «swinger» transcripts, notably for ribosomal RNAs. Congruence of DNA, RNA and peptides resulting from the same swinging process suggest that systematic nucleotide exchanges increase coding potential, and may add to evolutionary diversification of bacterial populations.