Metabolic engineering of tropane and nicotine alkaloid biosynthesis

Genetic knowledge on biosynthetic pathways and the regulation thereof is of crucial importance to bypass the low-product yield of various secondary metabolites in plant cells. To facilitate gene discovery in plant secondary metabolism, we have developed a comprehensive profiling approach that is based on functional genomics and can be applied on any plant system without a need for prior sequence knowledge. Jasmonate-induced changes have been monitored on the transcript and alkaloid profiles of tobacco and two other medicinal plants. Using cDNA-AFLP based transcript profiling, an inventory of hundreds of genes, potentially involved in plant secondary metabolism, has been built. A technology platform, especially driven towards the exploitation of plant cell cultures, for high-throughput isolation and functional analysis of these genes, has been established. At present, more than 50 tobacco BY-2 full-length open reading frames have been isolated and are currently subjected to functional analysis. In our tobacco BY-2 model system the overexpression of 22 genes resulted in three lines exhibiting an altered alkaloid accumulation pattern compared to controls. The genes derived from the tobacco transcriptional profiling are also used for the transformation of other plant species. So far, one of the tested genes has strongly influenced the tropane alkaloid biosynthesis, which is partly the same as for nicotine alkaloids. We have developed a technology platform called SOLUCEL that allows creating a novel toolbox for metabolic engineering of plant cells. It can be applied (i) to enhance the production of marketed high-value pharmaceuticals in plant cell cultures (ii) to develop reliable and reproducible sources of plant-derived molecules with potential pharmaceutical value, and (iii) to increase the chemical diversity of plant based molecules through Combinatorial Biochemistry.