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Title
Japanese:Redox regulation of NADP-malate dehydrogenase is vital for land plants under fluctuating light environment. 
English:Redox regulation of NADP-malate dehydrogenase is vital for land plants under fluctuating light environment. 
Author
Japanese: 若林憲一.  
English: Ken-Ichi Wakabayashi.  
Language English 
Journal/Book name
Japanese:Proceedings of the National Academy of Sciences of the United States of America 
English:Proceedings of the National Academy of Sciences of the United States of America 
Volume, Number, Page        
Published date Feb. 2021 
Publisher
Japanese: 
English: 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
Official URL https://europepmc.org/articles/PMC8017969
 
DOI https://doi.org/10.1073/pnas.2016903118
Abstract Many enzymes involved in photosynthesis possess highly conserved cysteine residues that serve as redox switches in chloroplasts. These redox switches function to activate or deactivate enzymes during light-dark transitions and have the function of fine-tuning their activities according to the intensity of light. Accordingly, many studies on chloroplast redox regulation have been conducted under the hypothesis that "fine regulation of the activities of these enzymes is crucial for efficient photosynthesis." However, the impact of the regulatory system on plant metabolism is still unclear. To test this hypothesis, we here studied the impact of the ablation of a redox switch in chloroplast NADP-malate dehydrogenase (MDH). By genome editing, we generated a mutant plant whose MDH lacks one of its redox switches and is active even in dark conditions. Although NADPH consumption by MDH in the dark is expected to be harmful to plant growth, the mutant line did not show any phenotypic differences under standard long-day conditions. In contrast, the mutant line showed severe growth retardation under short-day or fluctuating light conditions. These results indicate that thiol-switch redox regulation of MDH activity is crucial for maintaining NADPH homeostasis in chloroplasts under these conditions.

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