Plant Virus Vectors - Viruses have the following attractive features as vectors:

(i) viruses infect cells of adult plants,
(ii) they produce large number of copies per cell leading to gene amplification, and production of the recombinant protein in large quantities and
(iii) some viruses are systemic in that they spread throughout the plant.

Plant virus genomes do not integrate into the plant genome. As a result, they can not be used to produce stable and heritable transformations. But they can be used to express transgenes with a view to either improve the phenotypic performance of host plants or to produce large quantities of valuable proteins.