Symposium V: The Plasma Membrane: A Happening Place

Abs # 50003: Plasmodesmata: pathways for intercellular trafficking of macromolecules

Presenter:	Lucas, William J, wjlucas@ucdavis.edu
Authors	Lucas, William J (A)
Affiliations:	(A): University of California, Davis

It has long been known that plasmodesmata (PD) serve an important role in establishing cytoplasmic continuity between neighboring cells within plant tissues and organs. Recent studies have demonstrated that PD also have the capacity to mediate the cell-to-cell transport of macromolecules, including proteins and RNA. Initial insight into this unique function was gained through studies on plant viruses. An ever-increasing number of viruses have now been shown to encode non-structural proteins, termed movement proteins, that function in the transport of viral infectious material through PD. These findings led to the discovery that many plant proteins, including transcription factors, are also able to use this PD highway to traffic through cells of a particular tissue. Similar to viral movement proteins, a number of these endogenous proteins have the capacity to potentiate the cell-to-cell transport of mRNA. Interestingly, proteins that can gain entry into the phloem sieve tube system are able to move over long distances within the body of the plant. This special property of PD, to mediate the exchange of information molecules, established the concept that higher plants function as supracellular rather than multicellular organisms. Now that it has been unambiguously established that endogenous macromolecules have the capacity to function at a supracellular level, the challenge ahead is to identify the cellular components involved in both mediating and regulating this non-cell-autonomous translocation (NCAT) pathway. In this talk we will illustrate the emerging principles of plasmodesmal biology in areas of cell biology, physiology, developmental biology and whole plant signaling. The impact of these new paradigms on studies in plant biology will be discussed both in terms of RNA as a long-distance information macromolecule and the evolution of RNA surveillance fields (SurFs) within the plant kingdom.