Journal
PLANT AND CELL PHYSIOLOGY
Volume 60, Issue 11, Pages 2369-2381Publisher
OXFORD UNIV PRESS
DOI: 10.1093/pcp/pcz123
Keywords
Alternative oxidase; Arabidopsis thaliana; Carbon fluxes; High light; Mitochondrial thioredoxin; Oxygen-isotope fractionation
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Funding
- Alexander von Humboldt Foundation through the 'Severo Ochoa Programme for Centres of Excellence in RD' 2016-2019 [SEV-2015-0533]
- Spanish Ministry of Economy and Competitiveness (MINECO), through the 'Severo Ochoa Programme for Centres of Excellence in RD' 2016-2019 [SEV-2015-0533]
- Spanish Ministries Spanish Ministry of Science, Innovation and Universities [BFU2011-23294]
- Centre National de la Recherche Scientifique [12-BSV6-0011]
- Agence Nationale de la Recherche ANR-Blanc Cynthiol [12-BSV6-0011]
- MINECO [CTM2014-53902-C2-1-P]
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The alternative oxidase (AOX) constitutes a nonphosphorylating pathway of electron transport in the mitochondrial respiratory chain that provides flexibility to energy and carbon primary metabolism. Its activity is regulated in vitro by the mitochondrial thioredoxin (TRX) system which reduces conserved cysteines residues of AOX. However, in vivo evidence for redox regulation of the AOX activity is still scarce. In the present study, the redox state, protein levels and in vivo activity of the AOX in parallel to photosynthetic parameters were determined in Arabidopsis knockout mutants lacking mitochondrial trxo1 under moderate (ML) and high light (HL) conditions, known to induce in vivo AOX activity. In addition, C-13- and C-14-labeling experiments together with metabolite profiling were performed to better understand the metabolic coordination between energy and carbon metabolism in the trxo1 mutants. Our results show that the in vivo AOX activity is higher in the trxo1 mutants at ML while the AOX redox state is apparently unaltered. These results suggest that mitochondrial thiol redox systems are responsible for maintaining AOX in its reduced form rather than regulating its activity in vivo. Moreover, the negative regulation of the tricarboxylic acid cycle by the TRX system is coordinated with the increased input of electrons into the AOX pathway. Under HL conditions, while AOX and photosynthesis displayed similar patterns in the mutants, photorespiration is restricted at the level of glycine decarboxylation most likely as a consequence of redox imbalance.
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