1University of Rostock, Biology Institute, Albert Einstein Str. 3, 18059 Rostock, Germany; 2A. N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, Moscow 119899, Russia; 3M. M. Shemyakin & Yu. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya Str., 117997 Moscow, Russia; 4Institute of Plant Virology, Microbiology and Biosafety, Federal Biological Research Centre for Agriculture and Forestry, Messeweg 11/12, 38104 Braunschweig, Germany
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Accepted 23 March 2006.
The Tomato spotted wilt virus (TSWV) encoded NSm movement protein facilitates cell-to-cell spread of the viral genome through structurally modified plasmodesmata. NSm has been utilized as bait in yeast two-hybrid interaction trap screenings. As a result, a protein of unknown function, called At-4/1, was isolated from an Arabidopsis thaliana GAL4 activation domain-tagged cDNA library. Using poly-clonal antibodies against bacterially expressed At-4/1, Western blot analysis of protein extracts isolated from different plant species as well as genome database screenings showed that homologues of At-4/1 seemed to be encoded by many vascular plants. For subcellular localization studies, At-4/1 was fused to green fluorescent protein, and corresponding expression vectors were used in particle bombardment and agroinfiltration assays. Confocal laser scannings revealed that At-4/1 assembled in punctate spots at the cell periphery. The protein accumulated intracellularly in a polarized fashion, appearing in only one-half of a bombarded epidermal cell, and, moreover, moved from cell to cell, forming twin-structured bodies seemingly located at both orifices of the plasmodesmatal pore. In coexpression studies, At-4/1 colocalized with a plant virus movement protein TGBp3 known to reside in endoplasmic reticulum-derived membrane structures located in close vicinity to plasmodesmata. Thus, At-4/1 belongs to a new family of plant proteins capable of directed intra- and intercellular trafficking.
© 2006 The American Phytopathological Society