Metabolic engineering in plants involves the modification of intrinsic metabolic pathways to increase or reduce the flux towards particular endogenous compounds, or the introduction of completely new pathways to allow the production of compounds that are not usually synthesized in that species. Using sophisticated molecular tools, detailed knowledge of the target pathway, and state-of-the-art gene transfer technology, we have embarked on programs to engineer complex metabolic pathways in crops, such as the polyamine and terpenoid indole alkaloid pathways (secondary metabolism) as well as carbon dioxide fixation (primary metabolism). The polyamine pathway serves as a useful and relevant model to understand key factors controlling the expression of endogenous and heterologous genes in complex plant metabolic pathways. Polyamines play key roles in many developmental, physiological and biochemical processes, and they also act as anti-oxidants in the human diet. We are currently evaluating the role of polyamines in leaf development and senescence. Lessons learned from engineering the polyamine pathway in plants can be used to enhance the quality of crops by genetic engineering.
Another major focus of the metabolic engineering group is the development of different approaches to increase the biomass and productivity of crops by enhancing the uptake of nutrients and carbon dioxide. In this context, we have more than doubled the photosynthetic efficiency and tuber yield of potato plants by expressing a glycolate dehydrogenase polyprotein comprising all three subunits (D, E and F) of a bacterial glycolate dehydrogenase to circumvent the limitations of endogenous carbon assimilation.