title: Virus infection triggers widespread silencing of host genes by a distinct class of endogenous siRNAs in Arabidopsis.
abstract: Antiviral immunity controlled by RNA interference (RNAi) in plants and animals is thought to specifically target only viral RNAs by the virus-derived small interfering RNAs (siRNAs). Here we show that activation of antiviral RNAi in Arabidopsis plants is accompanied by the production of an abundant class of endogenous siRNAs mapped to the exon regions of more than 1,000 host genes and rRNA. These virus-activated siRNAs (vasiRNAs) are predominantly 21 nucleotides long with an approximately equal ratio of sense and antisense strands. Genetically, vasiRNAs are distinct from the known plant endogenous siRNAs characterized to date and instead resemble viral siRNAs by requiring Dicer-like 4 and RNA-dependent RNA polymerase 1 (RDR1) for biogenesis. However, loss of exoribonuclease4/thylene-insensitive5 enhances vasiRNA biogenesis and virus resistance without altering the biogenesis of viral siRNAs. We show that vasiRNAs are active in directing widespread silencing of the target host genes and that Argonaute-2 binds to and is essential for the silencing activity of vasiRNAs. Production of vasiRNAs is readily detectable in Arabidopsis after infection by viruses from two distinct supergroups of plant RNA virus families and is targeted for inhibition by the silencing suppressor protein 2b of Cucumber mosaic virus. These findings reveal RDR1 production of Arabidopsis endogenous siRNAs and identify production of vasiRNAs to direct widespread silencing of host genes as a conserved response of plants to infection by diverse viruses. A possible function for vasiRNAs to confer broad-spectrum antiviral activity distinct to the virus-specific antiviral RNAi by viral siRNAs is discussed.
authors.affiliation: Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521;
authors.forename: Mengji
authors.initials: M
authors.lastname: Cao
authors.affiliation: Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521; The State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China;
authors.forename: Peng
authors.initials: P
authors.lastname: Du
authors.affiliation: Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521;
authors.forename: Xianbing
authors.initials: X
authors.lastname: Wang
authors.affiliation: Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521;
authors.forename: Yun-Qi
authors.initials: YQ
authors.lastname: Yu
authors.affiliation: Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521;
authors.forename: Yan-Hong
authors.initials: YH
authors.lastname: Qiu
authors.affiliation: Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521;
authors.forename: Wanxiang
authors.initials: W
authors.lastname: Li
authors.affiliation: Department of Plant Pathology and Weed Science, Volcani Center, Bet Dagan 50250, Israel; and.
authors.forename: Amit
authors.initials: A
authors.lastname: Gal-On
authors.affiliation: National Citrus Engineering Research Center, Citrus Research Institute, Southwest University, Chongqing 400712, China.
authors.forename: Changyong
authors.initials: C
authors.lastname: Zhou
authors.affiliation: The State Key Laboratory of Protein and Plant Gene Research, College of Life Sciences, Peking University, Beijing 100871, China; shou-wei.ding@ucr.edu liyi@pku.edu.cn.
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.affiliation: Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521; shou-wei.ding@ucr.edu liyi@pku.edu.cn.
authors.forename: Shou-Wei
authors.initials: SW
authors.lastname: Ding
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000276:immunology / Q000821:virology; D029681:Arabidopsis Proteins / Q000235:genetics*; D015152:Blotting, Northern; D017799:Cucumovirus / Q000235:genetics / Q000276:immunology / Q000502:physiology; D060467:Disease Resistance / Q000235:genetics / Q000276:immunology; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions / Q000235:genetics / Q000276:immunology; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics / Q000276:immunology / Q000821:virology; D010942:Plant Viruses / Q000235:genetics* / Q000276:immunology / Q000502:physiology; D034622:RNA Interference; D018749:RNA, Plant / Q000235:genetics / Q000276:immunology; D034741:RNA, Small Interfering / Q000235:genetics* / Q000276:immunology
chemical_list: D029681:Arabidopsis Proteins; D018749:RNA, Plant; D034741:RNA, Small Interfering
keywords: RNA silencing; microbiology; plant biology; viral suppressor of RNAi