title: The 5' cap of tobacco mosaic virus (TMV) is required for virion attachment to the actin/endoplasmic reticulum network during early infection.
abstract: Almost nothing is known of the earliest stages of plant virus infections. To address this, we microinjected Cy3 (UTP)-labelled tobacco mosaic virus (TMV) into living tobacco trichome cells. The Cy3-virions were infectious, and the viral genome trafficked from cell to cell. However, neither the fluorescent vRNA pool nor the co-injected green fluorescent protein (GFP) left the injected trichome, indicating that the synthesis of (unlabelled) progeny viral (v)RNA is required to initiate cell-to-cell movement, and that virus movement is not accompanied by passive plasmodesmatal gating. Cy3-vRNA formed granules that became anchored to the motile cortical actin/endoplasmic reticulum (ER) network within minutes of injection. Granule movement on actin/ER was arrested by actin inhibitors indicating actin-dependent RNA movement. The 5' methylguanosine cap was shown to be required for vRNA anchoring to the actin/ER. TMV vRNA lacking the 5' cap failed to form granules and was degraded in the cytoplasm. Removal of the 3' untranslated region or replicase both inhibited replication but did not prevent granule formation and movement. Dual-labelled TMV virions in which the vRNA and the coat protein were highlighted with different fluorophores showed that both fluorescent signals were initially located on the same ER-bound granules, indicating that TMV virions may become attached to the ER prior to uncoating of the viral genome.
authors.affiliation: Institute of Molecular Plant Sciences, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK.
authors.forename: Nynne
authors.initials: N
authors.lastname: Christensen
authors.forename: Jens
authors.initials: J
authors.lastname: Tilsner
authors.forename: Karen
authors.initials: K
authors.lastname: Bell
authors.forename: Philippe
authors.initials: P
authors.lastname: Hammann
authors.forename: Richard
authors.initials: R
authors.lastname: Parton
authors.forename: Christophe
authors.initials: C
authors.lastname: Lacomme
authors.forename: Karl
authors.initials: K
authors.lastname: Oparka
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D016679:Genome, Viral; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007239:Infections / Q000235:genetics / Q000378:metabolism / Q000821:virology; D009068:Movement; D010829:Physiological Phenomena / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D021381:Protein Transport / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D014027:Tobacco Mosaic Virus / Q000235:genetics* / Q000378:metabolism*; D014771:Virion / Q000235:genetics / Q000378:metabolism
chemical_list: D000199:Actins; D012367:RNA, Viral; D049452:Green Fluorescent Proteins