title: A viral protein suppresses RNA silencing and binds silencing-generated, 21- to 25-nucleotide double-stranded RNAs.
abstract: Posttranscriptional gene silencing (PTGS) processes double-stranded (ds) RNAs into 21-25 nucleotide (nt) RNA fragments that direct ribonucleases to target cognate mRNAs. In higher plants, PTGS also generates mobile signals conferring sequence-specific silencing in distant organs. Since PTGS acts as an antiviral system in plants, successful virus infection requires evasion or suppression of gene silencing. Here we report that the 19 kDa protein (p19) of tombusviruses is a potent silencing suppressor that prevents the spread of mobile silencing signal. In vitro, p19 binds PTGS-generated, 21-25 nt dsRNAs and 21-nt synthetic dsRNAs with 2-nt 3' overhanging end(s), while it barely interacts with single-stranded (ss) RNAs, long dsRNAs or blunt-ended 21-nt dsRNAs. We propose that p19 mediates silencing suppression by sequestering the PTGS-generated 21-25 nt dsRNAs, thus depleting the specificity determinants of PTGS effector complexes. Moreover, the observation that p19-expressing transgenic plants show altered leaf morphology might indicate that the p19-targeted PTGS pathway is also important in the regulation of plant development.
authors.affiliation: Agricultural Biotechnology Center, Plant Biology Institute, PO Box 411, H-2101, Gödöllõ, Hungary. silhavy@abc.hu
authors.forename: Dániel
authors.initials: D
authors.lastname: Silhavy
authors.forename: Attila
authors.initials: A
authors.lastname: Molnár
authors.forename: Alessandra
authors.initials: A
authors.lastname: Lucioli
authors.forename: György
authors.initials: G
authors.lastname: Szittya
authors.forename: Csaba
authors.initials: C
authors.lastname: Hornyik
authors.forename: Mario
authors.initials: M
authors.lastname: Tavazza
authors.forename: József
authors.initials: J
authors.lastname: Burgyán
mesh_terms: D020868:Gene Silencing; D017343:Genes, Plant; D017930:Genes, Reporter; D008957:Models, Genetic; D010641:Phenotype; D018515:Plant Leaves / Q000821:virology; D030821:Plants, Genetically Modified; D017354:Point Mutation; D012323:RNA Processing, Post-Transcriptional; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000821:virology; D019183:Tombusviridae / Q000235:genetics / Q000378:metabolism*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; D014764:Viral Proteins