Tobacco mosaic virus and the virescence of biotechnology
There is a growing realization that a modern combination of molecular biology and agriculture will provide a photosynthetic basis for the biosynthesis of an increasing variety of complex and valuable molecules. This ‘greening’ of biotechnology may impact on the global environment in many beneficial ways, but will perhaps have its most significant impact on human health. In the past decade, the capacity to use plants as an expanded source of therapeutics has grown through the accelerated development of effective viral transfection vectors for gene transfer to cultivated crops. Recombinant vectors based on tobacco mosaic virus (TMV) and other members of the Tobamovirus genus are now used to transfect commercially meaningful quantities of plant biomass cultivated in enclosed greenhouses and multiacre fields. Viral RNA promoters are effectively manipulated for the synthesis of recombinant messenger RNAs in whole plants. Chimeric plant virus and virus–like particles are designed for peptide production and display from recombinant structural protein–gene fusions. Gene functions are assessed and modified by either virus–mediated expression or cytosolic inhibition of expression at the RNA level. Recombinant virus populations, propagated by inoculating plants with infectious RNA transcripts or recombinant virions, have proved to be genetically stable over product–manufacturing cycles. Large volumes of highly purified protein products isolated from transfected foliage conform reproducibly to the specifications required for well–characterized biologics. In some cases, they exceed the specific activities of molecules purified from alternative recombinant and native sources. The resulting products are then formulated according to the developing national regulatory guidelines appropriate for agriculture–based manufacturing. Each of these innovations was first realized by researchers using clones of tobamovirus genes and recombinant genomes. This progress is founded on the heritage of a century of fundamental TMV research.
