Molecular Plant-Microbe Interactions (Sep 2000)

Cell-to-Cell Movement of Potexviruses: Evidence for a Ribonucleoprotein Complex Involving the Coat Protein and First Triple Gene Block Protein

  • Tony J. Lough,
  • Natalie E. Netzler,
  • Sarah J. Emerson,
  • Paul Sutherland,
  • Fiona Carr,
  • David L. Beck,
  • William J. Lucas,
  • Richard L. S. Forster

DOI
https://doi.org/10.1094/MPMI.2000.13.9.962
Journal volume & issue
Vol. 13, no. 9
pp. 962 – 974

Abstract

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The triple gene block proteins (TGBp1-3) and coat protein (CP) of potexviruses are required for cell-to-cell movement. Separate models have been proposed for inter-cellular movement of two of these viruses, transport of intact virions, or a ribonucleoprotein complex (RNP) comprising genomic RNA, TGBp1, and the CP. At issue therefore, is the form(s) in which RNA transport occurs and the roles of TGBp1-3 and the CP in movement. Evidence is presented that, based on microprojectile bombardment studies, TGBp1 and the CP, but not TGBp2 or TGBp3, are co-translocated between cells with viral RNA. In addition, cell-to-cell movement and encapsidation functions of the CP were shown to be separable, and the rate-limiting factor of potexvirus movement was shown not to be virion accumulation, but rather, the presence of TGBp1-3 and the CP in the infected cell. These findings are consistent with a common mode of transport for potex-viruses, involving a non-virion RNP, and show that TGBp1 is the movement protein, whereas TGBp2 and TGBp3 are either involved in intracellular transport or interact with the cellular machinery/docking sites at the plasmodesmata.