Cellular and Molecular Studies of Tobamovirus Movement Proteins

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96-31124 Beachy Most plant viruses, including tobacco mosaic virus (TMV), use plasmodesmata, the cytoplasmic bridges between proximal cells, to spread to adjacent cells. Most plant viruses encode one or two proteins that are required for virus movement through the plasmodesmata. These proteins are termed movement proteins (MP). The latter apparently functions by modifying the size exclusion limits of plasmodesmata. The PI has constructed mutants of MP in which the latter is fused to the green fluorescent protein (GFP) of Aequorea victoria to study cellular distribution and mode of action of the MP. The general goals of this proposal are: to determine the time course of GFP-MP cellular distribution during the course of infection in protoplasts and in leaves; to create mutations in the MP that leads to accumulation of GFP-MP in specific cellular structures, but not in other; to isolate cellular structures that contain GFP-MP, to determine what cellular components are associated with GFP-MP; as well as studies that include detailed analyses of GFP-MP in cells. These studies will add significantly to our knowledge about the intra- and inter-cellular distribution of TMV, as well as our knowledge of the role of the cytoskeleton in the targeting and transport of proteins in plasmodesmata. %%% Most plant viruses have evolved the capacity to use components in host cells for viral genome replication, for translation of viral proteins, for sorting and packaging of viral components, for export, and for spreading to proximal cells. For the latter process, most viruses encode proteins that modify the size exclusion limit of plasmodesmata. These proteins are termed movement proteins (MP). Little is known about the molecular mechanism of the MP. The proposed studies will investigate the cellular localization and mode of action of the tobacco mosaic virus (TMV) MP. These studies will increase significantly our knowledge about the cellular distribution of TMV as well as the role of the cytoskeleton in the t argeting and, possibly, in the transport of MP to plasmodesmata. ***