DYNAMICS OF BEAN DWARF MOSAIC GEMINIVIRUS CELL-TO-CELL AND LONG-DISTANCE MOVEMENT IN PHASEOLUS-VULGARIS REVEALED, USING THE GREEN FLUORESCENT PROTEIN

The cell-to-cell and long-distance movement of the bipartite geminivir us, bean dwarf mosaic (BDMV), in Phaseolus vulgaris plants was examine d with the noninvasive reporter, the green fluorescent protein (GFP), A modified GFP gene (mGFP4) was inserted into the BDMV DNA-A component in place of the coat protein gene (BDMVA-mGFP4), and particle bombard ment was used to introduce viral DNA into bean seedlings (radicle and hypocotyl tissues), Fluorescence analysis of GFP expressed from BDMVA- mGFP4 established that particle bombardment introduced viral DNA only into epidermal cells, and the requirement for the DNA-B-encoded protei ns (BV1 and BC1) in the cell-to-cell movement of BDMVA-mGFP4, This GFP reporter system was used to follow the viral infection process from t he seedling stage throughout the entire plant life cycle, In inoculate d hypocotyls, BDMV moved from cell to cell through the cortex and show ed a striking phloem tropism, Upon entry into phloem tissues, BDMV mov ed rapidly toward the root via the long-distance transport system, and toward the shoot apex by a combination of cell-to-cell and long-dista nce movement, Analysis of GFP distribution in systemically infected ti ssues revealed that BDMV was restricted to phloem cells in both roots and stems, In systemically infected primary and trifoliolate leaves, B DMV infected phloem cells associated with all vein orders (first throu gh fifth), and the capacity of BDMV to exit from phloem tissue into no nphloem cells was correlated with the stage of plant development, Fina lly, fluorescence analysis of GFP in reproductive tissues established that BDMV infected flower, pod, and seed-coat tissues, but was exclude d from the embryo.