Virology

Viral DNA Relocation

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Science  16 Jul 2004:
Vol. 305, Issue 5682, pp. 311-313
DOI: 10.1126/science.305.5682.311d

For plant viruses to disseminate within host plants, viral DNA needs to traverse the cellulose cell wall to gain access to new target cells. How viruses can move within an individual infected plant has been controversial for the agronomically important group of plant viruses known as the geminiviruses. Three viral proteins mediate transport: the coat protein (CP), the nuclear shuttle protein (NSP), and the movement protein (MP). All three are implicated in forcing the transit of viral DNA through plasmodesmata— “tunnels” across plant cellulose walls. Hehnle et al. examined the binding characteristics of the three transport proteins to plasmid DNA. The data support a “couple-skating” model, in which NSP and MP cooperate in binding viral DNA. MP appears to insert itself and bind to single-stranded DNA segments within the double-stranded supercoiled DNA molecule. MP is membrane- anchored and thus should be able to cooperate with NSP to drag the viral DNA across the cell wall. MP would also appear to help to spread out the DNA at the cell membrane, which may ease its passage as it threads through the narrow plasmodesmata into the neighboring cell. — CA

J. Virol. 78, 7698 (2004).

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