Plant virus transport: motions of functional equivalence.

Plant virus cell-to-cell movement and subsequent systemic transport are governed by a series of mechanisms involving various virus and plant factors. Specialized virus encoded movement proteins (MPs) control the cell-to-cell transport of viral nucleoprotein complexes through plasmodesmata. MPs of different viruses have diverse properties and each interacts with specific host factors that also have a range of functions. Most viruses are then transported via the phloem as either nucleoprotein complexes or virions, with contributions from host and virus proteins. Some virus proteins contribute to the establishment and maintenance of systemic infection by inhibiting RNA silencing-mediated degradation of viral RNA. In spite of all the different movement strategies and the viral and host components, there are possible functional commonalities in virus-host interactions that govern viral spread through plants.