Plants are an inexpensive source of complex molecules. Several industries are based on chemical feedstocks of plant origin, ranging from flavors to pharmaceuticals. The biosynthetic pathways of plants may be more effectively manipulated through viral gene amplification than by conventional genetic engineering. We propose to amplify specific target RNAs in transgenic plants based on viral RNA replication. The 5' and 3' viral replication origins of tobacco mosaic virus will be combined with an internal target sequence to be amplified. Recombinant messenger RNA will be synthesized from a gene inserted into the tobacco chromosome under transcriptional control of a nominally constitutive promoter. In the presence of helper feasibility, we will quantify amplified gene expression using the messenger RNA for the enzyme chloramphenicol acetyltransferase (CAT) as a target sequence. %%% Because the levels of amplification and timing of expression will be controlled by the helper virus, this technique will significantly extend the types of genetic manipulations possible in transgenic crops. Efficient production of high value biochemicals in plants will create new opportunities for domestic growers and strengthen the ability of the agricultural sector of our economy to compete internationally.
