Formation of surface tubules and fluorescent foci in Arabidopsis thaliana protoplasts expressing a fusion between the green fluorescent protein and the cauliflower mosaic virus movement protein

The movement protein (MP) of cauliflower mosaic virus (CaMV) is a multifunctional protein that potentiates the cell-to-cell and long distance movement of the virus. Functional domains in the CaMV MP were determined by analyzing deletions in green fluorescent protein (GFP)-MP fusions transfected into Arabidopsis thaliana leaf protoplasts. GFP-MP accumulated at fluorescent foci at the cell periphery and in tubular structures extending from the protoplast surface. A region located near the center of MP was required for targeting GFP-MP to foci, whereas a larger region extending nearly to the N-terminus was needed for tubule formation. Cytoskeletal assembly inhibitors did not disrupt tubule formation or the accumulation of GFP-MP at foci, hut brefeldin A, which disrupts the plant cell endomembrane system, did interfere with the formation of tubules but not foci. (C) 2000 Academic Press.