The 5' cap of tobacco mosaic virus (TMV) is required for virion attachment to the actin/endoplasmic reticulum network during early infection

Nynne Christensen, Jens Tilsner, Karen Bell, Philippe Hammann, Richard Parton, Christophe Lacomme, Karl Oparka

Research output: Contribution to journalArticlepeer-review

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.
Original languageEnglish
Pages (from-to)536-551
Number of pages16
JournalTraffic
Volume10
Issue number5
Early online date11 Feb 2009
DOIs
Publication statusPublished - 31 May 2009

Keywords

  • direct fluorescence labelling
  • live cell imaging
  • methylguanosine cap
  • RNA anchoring
  • tobacco mosaic virus
  • viral RNA

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