PLANT-VIRUS GENE VECTORS FOR TRANSIENT EXPRESSION OF FOREIGN PROTEINSIN PLANTS

The development of plant virus gene vectors for expression of foreign genes in plants provides attractive biotechnological tools to compleme nt conventional breeding and transgenic methodology. The benefits of v irus-based transient RNA and DNA replicons versus transgenic gene expr ession include rapid and convenient engineering coupled with flexibili ty for expeditious application in various plant species. These charact eristics are especially advantageous when very high levels of gene exp ression are desired within a short time, although instability of the f oreign gene in the viral genome can present some problems. The strateg ies that have been tested for foreign gene expression in various virus -based vectors include gene replacement, gene insertion, epitope prese ntation, use of virus controlled gene expression cassettes, and comple mentation. Recent reports of the utililization of virus vectors for fo reign gene expression in fundamental research and biotechnology applic ations are discussed.