Collaborative Research: Metabolic fluxes from the Calvin-Benson cycle through the parallel shikimate and non-shikimate pathways in plants

Plants produce diverse aromatic compounds, which are critical ingredients of our food, medicine, fuel, and biomaterials. These compounds mainly come from aromatic amino acids (AAAs), which are produced from atmospheric carbon fixed by photosynthesis in plants. Normally, plants direct a small percentage of total fixed carbon towards AAAs, however, the principal investigator’s group has recently re-engineered the AAA synthesis pathway to use a much larger percentage of carbon from the Calvin-Benson cycle. This project investigates how carbon fixed by the Calvin-Benson cycle in photosynthesis flows through plant metabolic networks to produce AAAs and how plants adjust these carbon fluxes under different environmental conditions. The foundational knowledge gained about the system-level properties of plant metabolism allows the use of plants as an alternative platform to produce various aromatic compounds sustainably. The project recruits and trains students from diverse backgrounds and engages them directly in discovery-based systems biology research. In this way the next generation scientists acquire a broader understanding of complex plant metabolic systems. The shikimate pathway in plants is a central gateway directing carbon flux from the Calvin-Benson Cycle (CBC) of photosynthesis to biosynthesis of aromatic amino acids (AAAs). The principal investigator’s lab recently discovered novel genetic mutations that drastically enhance carbon flux to AAA biosynthesis via the shikimate and novel “non-shikimate” pathways. These mutants also elevate carbon dioxide (CO2) assimilation at the CBC. This project quantifies systems-wide carbon fluxes from the CBC to AAA biosynthesis and elucidates how the metabolic network of the CBC and parallel AAA pathways can flexibly produce AAAs under genetic and environmental perturbations. The project utilizes novel genetic mutants with integrated short to mid-term carbon-13 labeled CO2 feeding and metabolic flux modeling, together with biochemical and genetic analyses. The study re-defines the critical metabolic network connecting CO2 fixation and diverse aromatic production in plants. Quantitative understanding of this integrated metabolic system will enable sustainable production of diverse aromatic compounds, while efficiently capturing and sequestering CO2. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.