Functional analysis of a DNA-shuffled movement protein reveals that microtubules are dispensable for the cell-to-cell movement of tobacco mosaic virus.
Microtubules interact strongly with the viral movement protein (MP) of Tobacco mosaic virus (TMV) and are thought to transport the viral genome between plant cells. We describe a functionally enhanced DNA-shuffled movement protein (MP(R3)) that remained bound to the vertices of the cortical endoplasmic reticulum, showing limited affinity for microtubules. A single amino acid change was shown to confer the MP(R3) phenotype. Disruption of the microtubule cytoskeleton in situ with pharmacological agents, or by silencing of the alpha-tubulin gene, had no significant effect on the spread of TMV vectors expressing wild-type MP (MP(WT)) and did not prevent the accumulation of MP(WT) in plasmodesmata. Thus, cell-to-cell trafficking of TMV can occur independently of microtubules. The MP(R3) phenotype was reproduced when infection sites expressing MP(WT) were treated with a specific proteasome inhibitor, indicating that the degradation of MP(R3) is impaired. We suggest that the improved viral transport functions of MP(R3) arise from evasion of a host degradation pathway.
Gillespie
Trudi
T
Unit of Cell Biology, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, Scotland, United Kingdom.
Boevink
Petra
P
Haupt
Sophie
S
Roberts
Alison G
AG
Toth
Rachel
R
Valentine
Tracy
T
Chapman
Sean
S
Oparka
Karl J
KJ
D004279:DNA, Viral / Q000378:metabolism*; D005822:Genetic Vectors; D008870:Microtubules / Q000502:physiology* / Q000821:virology; D009068:Movement; D011523:Protoplasts / Q000502:physiology / Q000821:virology; D014026:Nicotiana / Q000502:physiology* / Q000821:virology; D014027:Tobacco Mosaic Virus / Q000235:genetics / Q000502:physiology*; D014162:Transfection
D004279:DNA, Viral