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Thioredoxin links redox to the regulation of fundamental processes of plant mitochondria
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Edité par CCSD ; National Academy of Sciences -
International audience. Mitochondria contain thioredoxin (Trx), a regulatory disulfide protein,and an associated flavoenzyme, NADPTrx reductase, whichprovide a link to NADPH in the organelle. Unlike animal and yeastcounterparts, the function of Trx in plant mitochondria is largelyunknown. Accordingly, we have applied recently devised proteomicapproaches to identify soluble Trx-linked proteins in mitochondriaisolated from photosynthetic (pea and spinach leaves) and heterotrophic(potato tubers) sources. Application of the mitochondrialextracts to mutant Trx affinity columns in conjunction with proteomicsled to the identification of 50 potential Trx-linked proteins functionalin 12 processes: photorespiration, citric acid cycle and associatedreactions, lipid metabolism, electron transport, ATP synthesistransformation, membrane transport, translation, protein assemblyfolding, nitrogen metabolism, sulfur metabolism, hormone synthesis,and stress-related reactions. Almost all of these targets were alsoidentified by a fluorescent gel electrophoresis procedure in whichreduction by Trx can be observed directly. Insomecases, the processestargeted by Trx depended on the source of the mitochondria. Theresults support the view that Trx acts as a sensor and enablesmitochondria to adjust key reactions in accord with prevailing redoxstate. These and earlier findings further suggest that, by sensingredox in chloroplasts and mitochondria, Trx enables the two organellesof photosynthetic tissues to communicate by means of anetwork of transportable metabolites such as dihydroxyacetonephosphate, malate, and glycolate. In this way, light absorbed andprocessed by means of chlorophyll can be perceived and function inregulating fundamental mitochondrial processes akin to its mode ofaction in chloroplasts.
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