title: A dual strategy for the suppression of host antiviral silencing: two distinct suppressors for viral replication and viral movement encoded by potato virus M.
abstract: Viruses encode RNA silencing suppressors to counteract host antiviral silencing. In this study, we analyzed the suppressors encoded by potato virus M (PVM), a member of the genus Carlavirus. In the conventional green fluorescent protein transient coexpression assay, the cysteine-rich protein (CRP) of PVM inhibited both local and systemic silencing, whereas the triple gene block protein 1 (TGBp1) showed suppressor activity only on systemic silencing. Furthermore, to elucidate the roles of these two suppressors during an active viral infection, we performed PVX vector-based assays and viral movement complementation assays. CRP increased the accumulation of viral RNA at the single-cell level and also enhanced viral cell-to-cell movement by inhibiting RNA silencing. However, TGBp1 facilitated viral movement but did not affect viral accumulation in protoplasts. These data suggest that CRP inhibits RNA silencing primarily at the viral replication step, whereas TGBp1 is a suppressor that acts at the viral movement step. Thus, our findings demonstrate a sophisticated viral infection strategy that suppresses host antiviral silencing at two different steps via two mechanistically distinct suppressors. This study is also the first report of the RNA silencing suppressor in the genus Carlavirus.
authors.affiliation: Department of Agricultural and Environmental Biology, The University of Tokyo, Tokyo, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Senshu
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Yamaji
authors.forename: Nami
authors.initials: N
authors.lastname: Minato
authors.forename: Takuya
authors.initials: T
authors.lastname: Shiraishi
authors.forename: Kensaku
authors.initials: K
authors.lastname: Maejima
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Chihiro
authors.initials: C
authors.lastname: Miura
authors.forename: Yutaro
authors.initials: Y
authors.lastname: Neriya
authors.forename: Shigetou
authors.initials: S
authors.lastname: Namba
mesh_terms: D017788:Carlavirus / Q000276:immunology* / Q000472:pathogenicity*; D020868:Gene Silencing; D054884:Host-Pathogen Interactions; D010935:Plant Diseases / Q000821:virology*; D014026:Nicotiana / Q000821:virology; D014764:Viral Proteins / Q000378:metabolism*
chemical_list: D014764:Viral Proteins