Integrated Studies on the Cellular, Physiological and Developmental Roles Played by Higher Plant Plasmodesmata

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9406974 Lucas This award supports studies on the molecular and cellular characterization of higher plant plasmodesmata (PD). The capacity of plasmodesmata to engage in macromolecular trafficking of proteins and nucleic acids will be studies using a combination of techniques. Functional and mutant viral movement proteins (MPs) will be used in microinjection studies to examine the molecular basis of the interaction between these MPs, their cognate viral RNA (vRNA), and plasmodesmata. This powerful combination of molecular virology and cell biology opens the way for the identification of the molecular determinants of virus-plant host specificity, as well as the elucidation of the functional domains on the viral MPs. The MPs of four plant viruses will be used in these studies; red clover necrotic mosaic virus (RCNMV), tobacco mosaic virus (TMV), sunn hemp mosaic virus (SHMV) and cucumber mosaic virus (CMV). In order to more fully understand the role played by plasmodesmata in the orchestration of plant development and physiological function, it is important that the sub-structural component (proteins) be isolated, cloned and sequenced. To this end, secondary PD will be isolated from TMV MP transgenic tobacco plants. The physiological and molecular basis for the TMV MP-induced alteration in carbon partitioning will be investigated using a range of experimental approaches. The reduction in root-to-shoot ratios observed in TMV MP transgenic tobacco will form the diagnostic basis for these studies. Tissue grafting experiments will permit the identification of the plant tissue involved in this reallocation phenomenon. The hypothesis that macromolecular (protein) trafficking through PD plays a role in plant development will be tested using the maize Knotted-1 mutant system. Results from these studies on the molecular determinants of viral MP-PD interaction will provide us with greater insights into the requirements for PD macromolecular trafficking. Purifica tion and identification of PD proteins will provide the foundation for a detailed structure/function analysis of this unique intercellular organelle. Details on the molecular events underlying the TMV MP- induced alteration in carbon partitioning will provide the foundation for the identification and study of endogenous signal/regulatory pathways that mediate in the integration of physiological processes from the tissue to the whole plant level. All such data on macromolecular transport through PD will contribute to testing the hypothesis that plants function as supracelluar rather than multicellular organisms. ***