**5. Conclusions**

In summary, we provided evidence that upregulation of PGLP activity leading to lowered 2-PG contents, is beneficial for maintaining photosynthesis under abiotic stresses. This is likely due to the removal of 2-PG-mediated negative metabolic feedback on central enzymes of the CB cycle and carbon export from the chloroplast. We suggest that an optimized photorespiratory flux can thus stabilize the production and allocation of organic carbon under unfavorable environmental conditions. The strategy presented here might have further implications for plant engineering approaches to generate highly productive and more stress-resistant plants for future climate scenarios.

**Author Contributions:** H.B. and S.T. conceived and supervised the project. C.H., S.T., and F.W. performed the research and analyzed data. M.H. provided experimental equipment and tools. S.T. wrote the article with additions and revisions from all authors. All authors have read and approved the final version of the manuscript.

**Funding:** This work was financially supported by the Deutsche Forschungsgemeinschaft (Research Unit FOR 1186 Promics, BA 1177/12 to H.B.) and the University of Rostock (to M.H. and S.T.). The LC-MS equipment at the University of Rostock was financed through a grant of the Hochschulbauförderungsgesetz (HBFG) program (INST 264/125-1 FUGG to H.B.).

**Acknowledgments:** We gratefully acknowledge Friedrich Kirsch (University of Rostock) for help with the GC analysis and Saskia Schwab (University of Rostock) for valuable technical assistance.

**Conflicts of Interest:** The authors declare no conflicts of interest.
