Integrated Studies on Cellular and Physiological Roles of Higher Plant Plasmodesmata

University Of California-Davis, Davis CA

Investigators

Abstract

Although it has long been known that, in plants, plasmodesmata (PD) establish cytoplasmic continuity between neighboring cells, it has only recently been established that these intercellular organelles play a role in the cell-to-cell trafficking of information macromolecules (proteins and RNA). The first direct evidence for this role came from genetic, molecular and cellular studies of viral infection in plants. In these infected plants, viral encoded movement proteins (MPs) traffic cell to cell through PD and, in this process, they mediate the spread of infectious RNA/DNA. In view of this finding, the hypothesis was advanced that plants similarly utilize this PD macromolecular trafficking pathway to exert positional-dependent control over developmental and physiological processes. The corollary to this hypothesis was advanced that plants function as unique supracellular, rather than multicellular, organisms. Support for this supracellular model has been accumulating; in this regard, a seminal discovery was that a number of plant transcription factors have now been shown to function in a non-cell-autonomous manner, via movement through PD. The picture that is emerging is that this ability of PD to transport macromolecules extended the properties evolved by the eukaryotic nuclear pore complex to the junctions between neighboring cells, and thereby allowed plants to develop this novel regulatory pathway. In the present work, experiments are aimed at characterizing the molecular constituents of PD and the non-cell-autonomous protein (NCAP) translocation pathway. For these studies a range of experimental techniques will be employed that combine genetic, molecular, cellular, physiological and developmental approaches. The major goal over this funding period will be to identify potential regulators of NCAP trafficking/PD function using a mutant screening approach in Arabidopsis. These studies should provide much needed information on the molecular components that function in the establishment and regulation of the non-cell-autonomous translocation pathway of plants. The importance of this information to the areas of integrative plant biology and development will likely be through the development of a greater understanding of the events that underlie whole plant signaling. These long-distance signals, delivered via the plant vascular system, are presently thought to function in the integration of the plant's response to environmental and biotic stresses. The requested funds will permit the training of junior scientists in this area of integrative plant biology. The importance of these scientists to our society will be through the application of knowledge towards the development of novel controls over plant processes, including the allocation of resources to targeted organs. Such applications could well have major ramifications in terms of agriculture and animal/human nutrition/health.