Molecular Plant
Volume 14, Issue 7, 5 July 2021, Pages 1104-1118
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Research Article
Two mitochondrial phosphatases, PP2c63 and Sal2, are required for posttranslational regulation of the TCA cycle in Arabidopsis

https://doi.org/10.1016/j.molp.2021.03.023Get rights and content
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Abstract

Protein phosphorylation is a well-established post-translational mechanism that regulates protein functions and metabolic pathways. It is known that several plant mitochondrial proteins are phosphorylated in a reversible manner. However, the identities of the protein kinases/phosphatases involved in this mechanism and their roles in the regulation of the tricarboxylic acid (TCA) cycle remain unclear. In this study, we isolated and characterized plants lacking two mitochondrially targeted phosphatases (Sal2 and PP2c63) along with pyruvate dehydrogenase kinase (PDK). Protein-protein interaction analysis, quantitative phosphoproteomics, and enzymatic analyses revealed that PDK specifically regulates pyruvate dehydrogenase complex (PDC), while PP2c63 nonspecifically regulates PDC. When recombinant PP2c63 and Sal2 proteins were added to mitochondria isolated from mutant plants, protein-protein interaction and enzymatic analyses showed that PP2c63 directly phosphorylates and modulates the activity of PDC, while Sal2 only indirectly affects TCA cycle enzymes. Characterization of steady-state metabolite levels and fluxes in the mutant lines further revealed that these phosphatases regulate flux through the TCA cycle, and that altered metabolism in the sal2 pp2c63 double mutant compromises plant growth. These results are discussed in the context of current models of the control of respiration in plants.

Key words

TCA cycle
pyruvate dehydrogenase phosphorylation
mitochondrial protein phosphatase
TCA cycle enzymes phosphorylation

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Published by the Molecular Plant Shanghai Editorial Office in association with Cell Press, an imprint of Elsevier Inc., on behalf of CSPB and CEMPS, CAS.