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

Paul F South,Amanda P Cavanagh,Helen W Liu,Donald R Ort

doi:10.1126/science.aat9077

Abstract

Photorespiration is required in C3 plants to metabolize toxic glycolate formed when ribulose-1,5-bisphosphate carboxylase-oxygenase oxygenates rather than carboxylates ribulose-1,5-bisphosphate. Depending on growing temperatures, photorespiration can reduce yields by 20 to 50% in C3 crops. Inspired by earlier work, we installed into tobacco chloroplasts synthetic glycolate metabolic pathways 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 photosynthetic quantum yield by 20%. Numerous homozygous transgenic lines increased biomass productivity between 19 and 37% in replicated field trials. These results show that engineering alternative glycolate metabolic pathways into crop chloroplasts while inhibiting glycolate export into the native pathway can drive increases in C3 crop yield under agricultural field conditions.

Highlights

Meeting food demands for the growing global human population requires improving crop productivity, and large gains are possible through enhancing photosynthetic efficiency
Introduction of pathway 3 increased biomass by 18% without RNA interference (RNAi) and 24% with RNAi, which were consistent with changes in photorespiratory metabolism and higher photosynthetic rates
We are optimistic that similar gains may be achieved and translated into increased yield in C3 grain crops because photorespiration is common to all C3 plants and higher photosynthetic rates under elevated CO2, which suppresses photorespiration and in

Summary

Introduction

Meeting food demands for the growing global human population requires improving crop productivity, and large gains are possible through enhancing photosynthetic efficiency. Photorespiration can reduce C3 crop photosynthetic efficiency by 20 to 50%. Various strategies exist for lowering the costs of photorespiration, chamber- and greenhouse-grown plants with altered photorespiratory pathways within the chloroplast have shown promising results, including increased photosynthetic rates and plant size. RATIONALE: To determine if alternative photorespiratory pathways could effectively improve C3 field crop productivity, we tested the performance of three alternative photorespiratory pathways in field-grown tobacco. All enzymes in the alternative pathway designs were directed to the chloroplast. RNA interference (RNAi) was used to down-regulate a native chloroplast glycolate transporter in the photorespiratory pathway, thereby limiting metabolite flux through the native pathway

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Conclusion