SBIR-STTR Award

Plants are an inexpensive source of complex molecules. Several industries are based on chemical feedstocks of plant origin, ranging from flavdrs to pharmaceuticals. The biosynthetic pathways of plants may be more effectively manipulated through viral gene amplification than by conventional genetic engineering. Researchers are amplifying specific target RNAs in transgenic plants based on viral RNA replication. The viral replication origins of tobacco mosaic virus are being combined with an internal target sequence to be amplified. Recombinant messenger RNA is being synthesized from a gene inserted into the tobacco chromosome under transcriptional control of a nominally constitutive promoter. In the presence of helper virus, this chimeric RNA is being replicated as an episome. To establish technical feasibility, researchers are quantifying amplified gene expression using the messenger RNA for the enzyme chloramphenicol acetyltransferase (CAT) as a target sequence. Because the lqvels of amplification and timing of expression are controlled by the helper virus, this technique extends the types of genetic manipulations possible in transgenic crops. Efficient production of high value biochemicals in plants are creating new opportunities for domestic growers and strengthening the ability of the agricultural sector to compete internationally.The potential commercial application as described by the awardee: This technology is being used to alter the quantities and composition of products derived from plants. Commercial focus is in the food additive and industrial enzyme markets.

The interaction of plants and their viruses present unique opportunities for the production of complex molecules. Tobacco Mosaic Virus (TMV) is the type member of the tobamovirus group and is one of the best understood viruses in all aspects of their biology. Using existing technology for the construction of recombinant RNA viruses and transgenic hosts, we propose to use viral RNA amplification for the synthesis of defined products in plants. In Phase II, we will determine the necessary and optimal configuration of episomal sequences to achieve the goal of controlled and biologically contained, high level gene expression in whole plants. %%% The most highly expressed genes in plants are found encoded in plant RNA viral genomes. In order to develop a plant virus as a gene vector, we will design constructs which retain the ability to generate infectious recombinants and, as such, will no longer be limited in their use as gene vectors. Thus, the production of complex molecules on a commercial basis will be greatly optimized.