Photorespiration is an essential process juxtaposed between plant carbon and nitrogen metabolism that responds to dynamic environments. Photorespiration recycles inhibitory intermediates arising from oxygenation reactions catalysed by Rubisco back into the C3 cycle, but it is unclear what proportions of its nitrogen-containing intermediates (glycine and serine) are exported into other metabolisms in vivo and how these pool sizes affect net CO2 gas exchange during photorespiratory transients. Here, to address this uncertainty, we measured rates of amino acid export from photorespiration using isotopically non-stationary metabolic flux analysis. This analysis revealed that ~23–41% of the photorespiratory carbon was exported from the pathway as serine under various photorespiratory conditions. Furthermore, we determined that the build-up and relaxation of glycine pools constrained a large portion of photosynthetic acclimation during photorespiratory transients. These results reveal the unique and important roles of glycine and serine in successfully maintaining various photorespiratory fluxes that occur under environmental fluctuations in nature and providing carbon and nitrogen for metabolism.
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All data used in this study are provided as Supplementary Information of the article or available upon request. Gas exchange data for modelling the photosynthetic responses to carbon dioxide concentration and photosynthetic responses during oxygen transients can be found on GitHub at https://github.com/codexf/Modeling_Photosynthesis.
Custom scripts for modelling the photosynthetic responses to carbon dioxide concentration and photosynthetic responses during oxygen transients can be found on GitHub at https://github.com/codexf/Modeling_Photosynthesis. A cloud-based workflow to run the Monte Carlo simulations for computing confidence intervals of metabolic fluxes can be found on GitHub at https://github.com/codexf/MFA_Cloud_Computing.
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We thank A. Ryce at Michigan State University (MSU) for experimental assistance; T. D. Sharkey (MSU) for providing lab space and guidance for performing the 14CO2 labelling experiments; Y. Xu and Y. Shachar-Hill (MSU) for helpful discussions on INST-MFA; J. Klug and C. Keilen (MSU Growth Chamber Facility) for plant maintenance; A. D. Jones, L. Chen and C. Johnny (MSU Mass Spectrometry and Metabolomics Core Facility) for advising metabolomics analyses; P. Bills (MSU IT Services), X. Wang and M. Parvizi (MSU Institute for Cyber-Enabled Research) for consulting on cloud computing and high-performance computing. The computational work was supported in part through the high-performance computing cluster and services provided by the Institute for Cyber-Enabled Research at MSU. The computational work was also supported in part through MSU’s Institute for Cyber-Enabled Research Cloud Computing Fellowship, with computational resources and services provided by Information Technology Services and the Office of Research and Innovation at MSU. We also thank J. Young for making INCA accessible and H. Stewart Williams for help establishing the online isotope analysis system. This work was supported by the US Department of Energy Office of Science, Basic Energy Sciences under Award DE- FG02-91ER20021 (B.J.W., X.F. and S.E.W.). This material is also based upon work supported in part by the Great Lakes Bioenergy Research Center, US Department of Energy, Office of Science, Office of Biological and Environmental Research under award number DE-SC0018409 (B.J.W.) and the National Science Foundation under grant number 2030337 (B.J.W. and L.M.G.). We also thank the constructive feedback from three anonymous reviewers, which greatly increased the quality and strength of this work.
The authors declare no competing interests.
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Supplementary Figs. 1–7, Tables 1 and 2 and Methods 1–4.
Supplementary Data 1–7
Supplementary Figs. 1–7, Tables 1 and 2 and Methods 1–4.
Supplementary Data 8
INCA model files in MATLAB readable format.
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Fu, X., Gregory, L.M., Weise, S.E. et al. Integrated flux and pool size analysis in plant central metabolism reveals unique roles of glycine and serine during photorespiration. Nat. Plants 9, 169–178 (2023). https://doi.org/10.1038/s41477-022-01294-9