Metabolic engineering of natural products in plants; tools of the trade and challenges for the future

Plant natural products play essential roles in plant survivability and many of them are used as nutrients, colorants, flavors, fragrances, and medicines. Genetic engineering of plants for natural products can help alleviate the demands for limited natural resources. Successes in enhancing production capacities have included manipulating blocks of genes coding for segments of pathways, over-expression of putative rate-limiting steps in pathways, expression of transcription factors regulating the entire metabolic pathways, and the construction of novel branch pathways capable of diverting carbon to the biosynthesis of unique metabolites in unexpected intracellular compartments. Further enhancements are likely if more efficient pathways can be constructed, providing for the efficient channeling of intermediates to final products, and if the means for sequestering natural products in planta can be accomplished.