Cell-to-cell movement of potexviruses: evidence for a ribonucleoprotein complex involving the coat protein and first triple gene block protein.
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 intercellular 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 potexviruses, 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.
Lough
T J
TJ
Horticulture and Food Research Institute of New Zealand, Plant Health and Development Group, Auckland. tlough@hort.cri.nz
Netzler
N E
NE
Emerson
S J
SJ
Sutherland
P
P
Carr
F
F
Beck
D L
DL
Lucas
W J
WJ
Forster
R L
RL
D019470:Biolistics; D002213:Capsid / Q000235:genetics*; D009154:Mutation; D030821:Plants, Genetically Modified / Q000166:cytology / Q000821:virology*; D017863:Potexvirus / Q000502:physiology*; D012261:Ribonucleoproteins / Q000502:physiology*
D012261:Ribonucleoproteins