VIRUS MOVEMENT IN INFECTED PLANTS

The movement of plant viruses from cell to cell is controlled by the action of virus-encoded proteins. With the realization that understanding the mechanism involved will lead to a broad comprehension of virus disease and may open new ways to engineer virus resistance, this phenomenon has recently received much attention. Sequence homologies between different movement proteins indicates that they may share a common origin and some functional similarities. However, groupings based upon protein structure, function as determined by complementation in double infections or host range, are not correlated. The proteins influence plasmodesmatal structure to allow the passage of viral genomes or virus particles, and one protein has been shown to have single-stranded nucleic acid binding properties. Transgenic plants, heterologous protein-expression systems, and cell biological approaches will determine how these proteins interact with host components to elicit complex structural changes which result in systemic virus invasion.