Breaking Through to the Other Side: How Plant Viruses Modify Plasmodesmata and the Plant Cell Wall.

Viruses are obligate intracellular parasites that rely on their hosts for the cellular machinery necessary for their replication and transmission to new hosts. Viruses are therefore invaluable for illuminating numerous facets of their hosts' biology. Plant viruses take advantage of the cell-to-cell connectivity provided by plasmodesmata for their movement from sites of replication to the vasculature for eventual systemic dissemination in their plant hosts, a strategy distinct from viruses that use animal and fungal hosts. Given their reliance on plasmodesmata for successful infection and spread in plant hosts, viruses remain powerful tools for probing plasmodesmal function and cell wall processes. The structure and function of plasmodesmata as well as the factors that contribute to plasmodesmal permeability are discussed here from the perspective of plasmodesmata as integral cell wall components. The relationship between the cell wall and plasmodesmata and how viruses affect both is also examined. The possibility that plasmodesmata are intriguing targets for designing novel strategies for crops with improved resistance to pathogens is also addressed.