Understanding, Prospecting and Engineering Photorespiration for Increased Crop Productivity

Population growth, increasing global affluence and an expanding bioeconomy are conspiring to increase mid-century agricultural demand by 120%, a challenge that current methods of increasing crop productivity cannot meet. Traits that have increased productivity during the Green Revolution are near maximum efficiency leaving photosynthesis as the only target to double yield potential. Photorespiration is required in C3 plants to metabolize glycolate formed when Rubisco oxygenates rather than carboxylates ribulose-1,5-bisphosphate. Depending on growing temperatures photorespiration can reduce yields by 20-50% in C3 crops. Optimization of the photorespiratory process by only 5% could be worth millions annually in increased productivity. Synthetic biology has provided new opportunities in altering photorespiratory metabolism to improve photosynthetic efficiency. Using a synthetic biology approach, we can now engineer and test hundreds of prototype plants from a range of multigene construct designs aimed at changing plant metabolism. Flux through tested synthetic pathways was maximized by inhibiting glycolate export from the chloroplast. Pathways tested for alternative photorespiration improved quantum yield of photosynthesis by 20% and increased productivity by 19-37% in replicated field experiments. In addition, synthetic biology and trait screening approaches can provide insight into photosynthetic and photorespiratory metabolism providing a novel parts prospecting approach to discovering crop improvement traits. The increased efficiency identified from alternative photorespiration leads to increases in thermal tolerance and has the potential for increased food production in related species. Synthetic engineering of alternative plant metabolisms along with identifying roles of photorespiration regulation and response to abiotic stress can create a platform for engineering increased agricultural production.