Synthetic photorespiratory bypass improves rice productivity by enhancing photosynthesis and nitrogen uptake

Abstract

Photorespiration, often considered as a wasteful process, is a key target for bioengineering to improve crop yields. Several photorespiratory bypasses have been designed to efficiently metabolize 2-phosphoglycolate and increase the CO2 concentration in chloroplasts, thereby reducing photorespiration. However, the suppression of primary nitrate assimilation remains an issue when photorespiration is inhibited. In this study, we designed a carbon and nitrogen metabolism-coupled photorespiratory bypass, termed the GCBG bypass, in rice (Oryza sativa) chloroplasts. Our results demonstrated efficient assembly and expression of the GCBG bypass in rice chloroplasts, which affected the levels of typical metabolites and their derivatives of natural photorespiration and enhanced the photosynthetic efficiency. Metabolomic analyses revealed that oxaloacetate, produced from glycolate in chloroplasts, positively impacted amino acid synthesis, energy metabolism, and sugar synthesis. The engineered GCBG plants showed an average yield increase of 19.0% (17.8-20.2%) compared to wild-type plants under natural growth conditions, alongside improved nitrogen uptake, which compensated for 44.1% of yield losses under nitrogen-limited conditions. In summary, the GCBG bypass substantially improved the photosynthetic efficiency, biomass and yield in rice by integrating carbon and nitrogen metabolism. This study introduces a strategy for engineering high-yielding rice or other crops with improved photosynthetic efficiency and nitrogen uptake.