Plants produce a vast array bio-active natural products to deter herbivores and pests and to enable inter-plant communication. Many of these bio-active natural products are used in human medicine. Typcially plants produce small amounts making the compounds difficult to isolate and highly expensive. Our basic research aims are to elucidate the pathways and genes involved in the formation of specific bio-active natural products belonging to the diterpenoid class and to use the approaches of synthetic biology to produce the compounds in high amounts using sunlight as the ultimate energy source.
In the evolution of photosynthetic organisms, the light driven energy supply provided by photosynthesis has been superimposed on a pre-existing set of primary metabolic reactions based on energy generation from oxidation of chemical compounds present in the environment and formation and turn-over of carbohydrates as a mean to channel energy flux and carbon into specific biosynthetic pathways. Photosynthetic organisms, such as cyanobacteria, mosses and plants, are thus amenable to the use of synthetic biology approaches aimed at tapping directly into, and prioritizing the energy output from photosynthesis to meet human demands for efficient production systems for desired bio-active natural products like structurally complex diterpenoids. The transfer of entire biosynthetic pathways for bio-active natural products into the chloroplast stroma or thylakoid membranes and the design of a supramolecular photosystem I complex into which the biosynthetic enzymes for bioactive natural product synthesis (cytochromes P450s and terpenoid synthases) are incorporated as fusion proteins using selected small subunits of the photosystem I complex as membrane anchors, will be discussed.