Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field

Authors: South, Paul; CAVANAGH, AMANDA - University Of Illinois; LIU, HELEN - University Of Illinois; ORT, DONALD - University Of Illinois

Submitted to: Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2018
Publication Date: 1/4/2019
Citation: South, P.F., Cavanagh, A.P., Liu, H.W., Ort, D.R. 2019. Synthetic glycolate metabolism pathways stimulate crop growth and productivity in the field. Science. 363(6422). https://doi.org/10.1126/science.aat9077.
DOI: https://doi.org/10.1126/science.aat9077

Interpretive Summary: C3 crops such as wheat, rice, and soybean undergo a process called photorespiration. Depending on growing temperatures photorespiration can reduce crop yields by 20-50%. Reduction in crop yields from photorespiration is from the production of byproducts such as glycolate which is toxic to the plant. To reduce crop losses due to photorespiration we engineered the model crop tobacco with an alternative metabolic pathway. In addition, to maximize use of the alternative pathway in plants we used RNA interference to reduce transport of the byproduct glycolate through the native photorespiration pathway. Top performing plant lines were able to increase productivity and increase biomass yields by >40% in field trials. These results provide compelling proof-of-concept that engineering alternative glycolate metabolic pathways into crops while inhibiting glycolate export into the native pathway can drive significant increases in C3 crop yield.

Technical Abstract: Photorespiration is required in C3 plants to metabolize toxic 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. Inspired by earlier work, we installed synthetic glycolate metabolic pathways into tobacco chloroplasts that are thought to be more efficient than the native pathway. Flux through the synthetic pathways was maximized by inhibiting glycolate export from the chloroplast. The synthetic pathways tested improved quantum yield by 20%. The top performing homozygous transgenic lines increased productivity by >40% in replicated field trials. These results provide compelling proof-of-concept that engineering alternative glycolate metabolic pathways into crop chloroplasts while inhibiting glycolate export into the native pathway can drive significant increases in C3 crop yield.