title: Modification of small RNAs associated with suppression of RNA silencing by tobamovirus replicase protein.
abstract: Plant viruses act as triggers and targets of RNA silencing and have evolved proteins to suppress this plant defense response during infection. Although Tobacco mosaic tobamovirus (TMV) triggers the production of virus-specific small interfering RNAs (siRNAs), this does not lead to efficient silencing of TMV nor is a TMV-green fluorescent protein (GFP) hybrid able to induce silencing of a GFP-transgene in Nicotiana benthamiana, indicating that a TMV silencing suppressor is active and acts downstream of siRNA production. On the other hand, TMV-GFP is unable to spread into cells in which GFP silencing is established, suggesting that the viral silencing suppressor cannot revert silencing that is already established. Although previous evidence indicates that the tobamovirus silencing suppressing activity resides in the viral 126-kDa small replicase subunit, the mechanism of silencing suppression by this virus family is not known. Here, we connect the silencing suppressing activity of this protein with our previous finding that Oilseed rape mosaic tobamovirus infection leads to interference with HEN1-mediated methylation of siRNA and micro-RNA (miRNA). We demonstrate that TMV infection similarly leads to interference with HEN1-mediated methylation of small RNAs and that this interference and the formation of virus-induced disease symptoms are linked to the silencing suppressor activity of the 126-kDa protein. Moreover, we show that also Turnip crinkle virus interferes with the methylation of siRNA but, in contrast to tobamoviruses, not with the methylation of miRNA.
authors.affiliation: Department of Plant Physiology, Botanical Institute, University of Basel, Switzerland.
authors.forename: Hannes
authors.initials: H
authors.lastname: Vogler
authors.forename: Rashid
authors.initials: R
authors.lastname: Akbergenov
authors.forename: Padubidri V
authors.initials: PV
authors.lastname: Shivaprasad
authors.forename: Vy
authors.initials: V
authors.lastname: Dang
authors.forename: Monika
authors.initials: M
authors.lastname: Fasler
authors.forename: Myoung-Ok
authors.initials: MO
authors.lastname: Kwon
authors.forename: Saule
authors.initials: S
authors.lastname: Zhanybekova
authors.forename: Thomas
authors.initials: T
authors.lastname: Hohn
authors.forename: Manfred
authors.initials: M
authors.lastname: Heinlein
mesh_terms: D000595:Amino Acid Sequence; D015967:Gene Expression Regulation, Viral; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000037:antagonists & inhibitors / Q000235:genetics; D008745:Methylation; D008969:Molecular Sequence Data; D009154:Mutation; D010935:Plant Diseases / Q000821:virology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism*; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics / Q000378:metabolism*; D014026:Nicotiana / Q000821:virology*; D017898:Tobamovirus / Q000201:enzymology / Q000235:genetics*; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D034741:RNA, Small Interfering; D014764:Viral Proteins; D049452:Green Fluorescent Proteins; D012324:RNA-Dependent RNA Polymerase