title: RNA-dependent RNA polymerase 1 from Nicotiana tabacum suppresses RNA silencing and enhances viral infection in Nicotiana benthamiana.
abstract: Endogenous eukaryotic RNA-dependent RNA polymerases (RDRs) produce double-stranded RNA intermediates in diverse processes of small RNA synthesis in RNA silencing pathways. RDR6 is required in plants for posttranscriptional gene silencing induced by sense transgenes (S-PTGS) and has an important role in amplification of antiviral silencing. Whereas RDR1 is also involved in antiviral defense in plants, this does not necessarily proceed through triggering silencing. In this study, we show that Nicotiana benthamiana transformed with RDR1 from Nicotiana tabacum (Nt-RDR1 plants) exhibits hypersusceptibility to Plum pox potyvirus and other viruses, resembling RDR6-silenced (RDR6i) N. benthamiana. Analysis of transient induction of RNA silencing in N. benthamiana Nt-RDR1 and RDR6i plants revealed that Nt-RDR1 possesses silencing suppression activity. We found that Nt-RDR1 does not interfere with RDR6-dependent siRNA accumulation but turns out to suppress RDR6-dependent S-PTGS. Our results, together with previously published data, suggest that RDR1 might have a dual role, contributing, on one hand, to salicylic acid-mediated antiviral defense, and suppressing, on the other hand, the RDR6-mediated antiviral RNA silencing. We propose a scenario in which the natural loss-of-function variant of RDR1 in N. benthamiana may be the outcome of selective pressure to maintain a high RDR6-dependent antiviral defense, which would be required to face the hypersensitivity of this plant to a large number of viruses.
authors.affiliation: State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Xiao-Bao
authors.initials: XB
authors.lastname: Ying
authors.forename: Li
authors.initials: L
authors.lastname: Dong
authors.forename: Hui
authors.initials: H
authors.lastname: Zhu
authors.forename: Cheng-Guo
authors.initials: CG
authors.lastname: Duan
authors.forename: Quan-Sheng
authors.initials: QS
authors.lastname: Du
authors.forename: Dian-Qiu
authors.initials: DQ
authors.lastname: Lv
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Fang
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: Garcia
authors.forename: Rong-Xiang
authors.initials: RX
authors.lastname: Fang
authors.forename: Hui-Shan
authors.initials: HS
authors.lastname: Guo
mesh_terms: D018506:Gene Expression Regulation, Plant; D010935:Plant Diseases / Q000235:genetics*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000821:virology; D017801:Plum Pox Virus; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics / Q000821:virology*
chemical_list: D018749:RNA, Plant; D034741:RNA, Small Interfering; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase
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