For over 10 years, TMV -based vectors have been used as plant expression tools to examine gene regulation and function, protein processing, pathogen elicitors, to manipulate biosynthetic pathways, and to produce high levels of enzymes, proteins, or peptides of interest in different locations in a plant cell. TMV vectors often exhibit genetic stability of foreign RNA sequences through multiple passages in plant hosts. Foreign coding sequences can be expressed in plants where the stability, intracellular fate and enzymatic or biological activities of the recombinant proteins can be rapidly evaluated and optimized. These properties make viral vectors attracti ve expression vehicles for testing and production of a wide variety of recombinant peptides and proteins, for structural analyses of post-translational modifications and for assessing gene function and metabolic control. Finally, the utility of both CP fusion and dual subgenomic vectors has extended beyond the laboratory and greenhouse to field-scale production and purification of recombinant products for commercial use (Grill, 1992; Grill, 1993; Turpen et at. , 1997). REFERENCES Copeman RJ, Hartman IR and Watterson IC. 1969. Tobacco mosaic virus in inoculated and systemically infected tobacco leaves. Phytopathology 59: 1012-1013. Dawson WO, Beck DL, Knorr DA and Grantham GL. 1986. cDNA cloning of the complete genome of tobacco mosaic virus and production of infectious transcripts. Proc. Natl. Acad. Sci. (USA) 83: 1832-1836. Dawson WO and Lehto KM. 1990. Regulation of tobamovirus gene expression. Ad. Virus Res. 38:307-342. Dawson WOo 1992. Tobamovirus-Plant Interactions. Virology 186:359-367.
