RNAi Antiviral Immune Pathway In Laodelphax Striatellus Modulate The Infection Of Southern Rice Black-streaked Dwarf Virus

Southern rice black-streaked dwarf virus(SRBSDV),a member of genus Fijivirus,family Reoviridae,is transmitted by insect vectors white backed planthopper(WBPH),sogatella furcifera in a persistent-propagative manner and has been one kind of the viruses which causes enormous losses of rice production in Southern China.Small brown planthopper(SBPH),Laodelphax striatellus can also acquire SRBSDV,but can not transmit it because SRBSDV cannot overcome the midgut escape barrier in the body of SBPH.Moreover,the infection rate and propagation speed of SRBSDV in SBPH cultured cells is significantly lower than those in WBPH cultured cells without the restriction of organizational barriers.Therefore,we deduced that RNA interference(RNAi)antiviral immune pathway of SBPH may inhibit the infection and proliferation of SRBSDV in the midgut epithelial cells,leading to the restriction of viral dissemination from midgut.In order to confirm our postulation,we used these technologies,including synthesis of dsRNA,RNA interference and SBPH cultured cells to study the interaction between SRBSDV and SBPH.In this study,to identify which key factors of RNAi antiviral immune pathway of SBPH could inhibit the infection and proliferation of SRBSDV in SBPH cultured cells,the double-stranded RNAs(dsRNAs)corresponding to the genes of RNAi antiviral immune pathway of SBPH,including argonaute 1(Ago1),argonaute 2(Ago2),Dicer 1(DCL1),Dicer 2(DCL2),systemic RNA interference defective-1(SID-1)and Piwi,was synthesized in vitro.Immunofluorescence showed that but dsDCL2 and dsAgo2 not others treatment did promote the infection and replication of SRBSDV in SBPH cultured cells compared with that of treatment with dsGFP.RT-qPCR further confirmed that knockdown of DCL2 and Ago2 expression due to RNAi induced by dsDCL2 and dsAgo2 significantly increased the accumulation of SRBSDV in the SBPH cultured cells.Therefore,the study not only testified RNAi antiviral pathway indeed existed in cells of SBPH,which mudulated the infection and replication of SRBSDV in the vector cells,but also the important factors in RNAi antiviral pathway were DCL2 and Ago2.It will lay the foundations for the future to further study the mechanism of RNAi antivital pathway in SBPH challenged by virus pathogeny and to explore new direction in order to block Southern rice black-streaked dwarf disease caused by SRBSDV.