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| 2. |
- Møller, Ian Max, et al.
(författare)
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Matrix Redox Physiology Governs the Regulation of Plant Mitochondrial Metabolism through Posttranslational Protein Modifications
- 2020
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Ingår i: The Plant cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 32:3, s. 573-594
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Forskningsöversikt (refereegranskat)abstract
- Mitochondria function as hubs of plant metabolism. Oxidative phosphorylation produces ATP, but it is also a central high-capacity electron sink required by many metabolic pathways that must be flexibly coordinated and integrated. Here, we review the crucial roles of redox-associated posttranslational protein modifications (PTMs) in mitochondrial metabolic regulation. We discuss several major concepts. First, the major redox couples in the mitochondrial matrix (NAD, NADP, thioredoxin, glutathione, and ascorbate) are in kinetic steady state rather than thermodynamic equilibrium. Second, targeted proteomics have produced long lists of proteins potentially regulated by Cys oxidation/thioredoxin, Met-SO formation, phosphorylation, or Lys acetylation, but we currently only understand the functional importance of a few of these PTMs. Some site modifications may represent molecular noise caused by spurious reactions. Third, different PTMs on the same protein or on different proteins in the same metabolic pathway can interact to fine-tune metabolic regulation. Fourth, PTMs take part in the repair of stress-induced damage (e.g., by reducing Met and Cys oxidation products) as well as adjusting metabolic functions in response to environmental variation, such as changes in light irradiance or oxygen availability. Finally, PTMs form a multidimensional regulatory system that provides the speed and flexibility needed for mitochondrial coordination far beyond that provided by changes in nuclear gene expression alone.
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| 3. |
- Voon, Chia Pao, et al.
(författare)
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ATP compartmentation in plastids and cytosol of Arabidopsis thaliana revealed by fluorescent protein sensing
- 2018
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 115:45, s. E10778-E10787
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Tidskriftsartikel (refereegranskat)abstract
- Matching ATP: NADPH provision and consumption in the chloroplast is a prerequisite for efficient photosynthesis. In terms of ATP: NADPH ratio, the amount of ATP generated from the linear electron flow does not meet the demand of the Calvin-Benson-Bassham (CBB) cycle. Several different mechanisms to increase ATP availability have evolved, including cyclic electron flow in higher plants and the direct import of mitochondrial-derived ATP in diatoms. By imaging a fluorescent ATP sensor protein expressed in living Arabidopsis thaliana seedlings, we found that MgATP(2-) concentrations were lower in the stroma of mature chloroplasts than in the cytosol, and exogenous ATP was able to enter chloroplasts isolated from 4- and 5-day-old seedlings, but not chloroplasts isolated from 10- or 20-day-old photosynthetic tissues. This observation is in line with the previous finding that the expression of chloroplast nucleotide transporters (NTTs) in Arabidopsis mesophyll is limited to very young seedlings. Employing a combination of photosynthetic and respiratory inhibitors with compartment-specific imaging of ATP, we corroborate the dependency of stromal ATP production on mitochondrial dissipation of photosynthetic reductant. Our data suggest that, during illumination, the provision and consumption of ATP: NADPH in chloroplasts can be balanced by exporting excess reductants rather than importing ATP from the cytosol.
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| 4. |
- Wagner, Stephan, et al.
(författare)
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Mitochondrial energy signaling and its role in the low-oxygen stress response of plants
- 2018
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Ingår i: Plant Physiology. - : Oxford University Press (OUP). - 0032-0889 .- 1532-2548. ; 176:2, s. 1156-1170
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Tidskriftsartikel (refereegranskat)abstract
- Cells of complex organisms typically rely on mitochondria for energy provision. The amount of energy required to sustain cellular activity can vary strongly depending on external conditions. Vice versa, constraints on respiratory activity due to metabolic status or stress insult require mitochondrial signaling to coordinate cellular physiology with the function of the organelle. In this update, we review recent insights into plant mitochondrial energy signaling in the light of their significance to stress acclimation. First, we focus on the characteristic adjustments of the nuclear transcriptome that occur after pharmacological inhibition of the mitochondrial electron transport chain as the output of mitochondrial retrograde signaling. Second, we discuss the proteins that have recently been identified as regulators of the transcript responses and the emerging picture of their action as a signaling network. We then pose the question of how well our current models of inducing mitochondrial dysfunction relate to conditions that plants face naturally. We reason that low-oxygen stress shows striking similarities with electron transport inhibitors with respect to their impact on mitochondrial energy physiology upstream, as well as the cellular transcriptomic response. Finally, we highlight and discuss changes in mitochondrial physiology that are common to both stimuli as candidates for upstream signals. The aim of this update is to better define the physiological context in which mitochondrial signaling operates to provide new directions for future research.RESPONSES TO MITOCHONDRIAL ENERGY SIGNALING AT THE TRANSCRIPT LEVEL
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| 5. |
- Wagner, Stephan, et al.
(författare)
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Multiparametric real-time sensing of cytosolic physiology links hypoxia responses to mitochondrial electron transport
- 2019
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137.
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Tidskriftsartikel (refereegranskat)abstract
- Hypoxia regularly occurs during plant development and can be induced by the environment through, for example, flooding. To understand how plant tissue physiology responds to progressing oxygen restriction, we aimed to monitor subcellular physiology in real time and in vivo. We establish a fluorescent protein sensor-based system for multiparametric monitoring of dynamic changes in subcellular physiology of living Arabidopsis thaliana leaves and exemplify its applicability for hypoxia stress. By monitoring cytosolic dynamics of (magnesium adenosine 5'-triphosphate), free calcium ion concentration, pH, NAD redox status, and glutathione redox status in parallel, linked to transcriptional and metabolic responses, we generate an integrated picture of the physiological response to progressing hypoxia. We show that the physiological changes are surprisingly robust, even when plant carbon status is modified, as achieved by sucrose feeding or extended night. Inhibition of the mitochondrial respiratory chain causes dynamics of cytosolic physiology that are remarkably similar to those under oxygen depletion, highlighting mitochondrial electron transport as a key determinant of the cellular consequences of hypoxia beyond the organelle. A broadly applicable system for parallel in vivo sensing of plant stress physiology is established to map out the physiological context under which both mitochondrial retrograde signalling and low oxygen signalling occur, indicating shared upstream stimuli.
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