Plasmodesmata control the cell-to-cell trafficking of viral and endogenous macromolecules

Studies originating with plant viruses led to the concept that plasmodesmata potentiate the cell-to-cell trafficking of viral and endogenous proteins and nucleoprotein complexes. In this article, we develop the theme that, at the tissue/organ level, cell-to-cell trafficking of information molecules enables noncell-autonomous control over a range of processes, whereas at the organismal level, the phloem serves as an information superhighway. The capacity to deliver proteins and nucleoprotein complexes, over long distances, allowed for the development of a viral surveillance/resistance mechanism, as well as the integration of processes at the whole-plant level.