The Movement Protein of Some Plant Viruses

Abstract

Plant viral infections spread from cell to cell through plasmodesmata. However, normal plasmodesmata do not allow the transit of the infectious material and viral infection often modifies their structure. Cell-to-cell spread (movement, transport) requires a virus-coded protein which presumably carries out the modification. By Western blot and immunoelectron microscopy, the movement proteins of alfalfa, tobacco and cauliflower mosaic viruses were detected in cell walls and/or plasmodesmata of systemic or hypersensitive hosts, supporting the assumptions made above. To prepare the spread factors of alfalfa mosaic virus (P3, 32 kDa) and tobacco mosaic virus (30 kDa) in the amount required for biochemical studies, we expressed those proteins in Saccharomyces cerevisiae using a shuttle expression vector. A 12-amino acid N-terminal deletion of P3 was also produced and purified to near homogeneity.