Nucleic acid transport in plant-pathogen interactions.

Inter- and intracellular transport of nucleic acids during plant-pathogen interaction is described on the examples of cell-to-cell movement of plant viruses and nuclear import of Agrobacterium T-DNA. In both cases, the transport process is mediated by specialized proteins produced by the pathogen. Plant virus movement occurs through the intercellular connections, plasmodesmata. In this process, the viral genomic nucleic acid is bound by virus-encoded movement protein. The nucleoprotein complex is then targeted to plasmodesmata, potentially via interaction with the host cell cytoskeleton. Prior to translocation, the plasmodesmal channel is dilated by the movement of protein. Nuclear import of Agrobacterium T-DNA is also mediated by bacterial proteins associated with the transported nucleic acid molecule. Specifically, the VirD2 and VirE2 proteins complex with the transferred DNA, providing it with the nuclear localization signals (NLSs). The VirD2 NLS is an evolutionarily conserved signal, active both in plant and animal cells. In contrast, the VirE2 NLS is plant-specific. Both VirD2 and VirE2 NLSs most likely interact with the plant cell nuclear import machinery to initiate the transport process.