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Keech, Olivier
Publications (10 of 23) Show all publications
Sylvestre-Gonon, E., Law, S. R., Schwartz, M., Robe, K., Keech, O., Didierjean, C., . . . Hecker, A. (2019). Functional, Structural and Biochemical Features of Plant Serinyl-Glutathione Transferases. Frontiers in Plant Science, 10, Article ID 608.
Open this publication in new window or tab >>Functional, Structural and Biochemical Features of Plant Serinyl-Glutathione Transferases
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2019 (English)In: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 10, article id 608Article, review/survey (Refereed) Published
Abstract [en]

Glutathione transferases (GSTs) belong to a ubiquitous multigenic family of enzymes involved in diverse biological processes including xenobiotic detoxification and secondary metabolism. A canonical GST is formed by two domains, the N-terminal one adopting a thioredoxin (TRX) fold and the C-terminal one an all-helical structure. The most recent genomic and phylogenetic analysis based on this domain organization allowed the classification of the GST family into 14 classes in terrestrial plants. These GSTs are further distinguished based on the presence of the ancestral cysteine (Cys-GSTs) present in TRX family proteins or on its substitution by a serine (Ser-GSTs). Cys-GSTs catalyze the reduction of dehydroascorbate and deglutathionylation reactions whereas Ser-GSTs catalyze glutathione conjugation reactions and eventually have peroxidase activity, both activities being important for stress tolerance or herbicide detoxification. Through non-catalytic, so-called ligandin properties, numerous plant GSTs also participate in the binding and transport of small heterocyclic ligands such as flavonoids including anthocyanins, and polyphenols. So far, this function has likely been underestimated compared to the other documented roles of GSTs. In this review, we compiled data concerning the known enzymatic and structural properties as well as the biochemical and physiological functions associated to plant GSTs having a conserved serine in their active site.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
photosynthetic organisms, phylogeny, structure, glutathione transferases, ligandin property, secondary metabolism, xenobiotic detoxification
National Category
Botany Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-159853 (URN)10.3389/fpls.2019.00608 (DOI)000468726200001 ()
Funder
Swedish Research Council, 621-2014-4688The Kempe Foundations
Available from: 2019-06-11 Created: 2019-06-11 Last updated: 2019-06-11Bibliographically approved
Law, S. R., Chrobok, D., Juvany, M., Delhomme, N., Lindén, P., Brouwer, B., . . . Keech, O. (2018). Darkened leaves use different metabolic strategies for senescence and survival. Plant Physiology, 177(1), 132-150
Open this publication in new window or tab >>Darkened leaves use different metabolic strategies for senescence and survival
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2018 (English)In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 177, no 1, p. 132-150Article in journal (Refereed) Published
Abstract [en]

In plants, an individually darkened leaf initiates senescence much more rapidly than a leaf from a whole darkened plant. Combining transcriptomic and metabolomic approaches in Arabidopsis (Arabidopsis thaliana), we present an overview of the metabolic strategies that are employed in response to different darkening treatments. Under darkened plant conditions, the perception of carbon starvation drove a profound metabolic readjustment in which branched-chain amino acids and potentially monosaccharides released from cell wall loosening became important substrates for maintaining minimal ATP production. Concomitantly, the increased accumulation of amino acids with a high nitrogen-carbon ratio may provide a safety mechanism for the storage of metabolically derived cytotoxic ammonium and a pool of nitrogen for use upon returning to typical growth conditions. Conversely, in individually darkened leaf, the metabolic profiling that followed our 13C-enrichment assays revealed a temporal and differential exchange of metabolites, including sugars and amino acids, between the darkened leaf and the rest of the plant. This active transport could be the basis for a progressive metabolic shift in the substrates fueling mitochondrial activities, which are central to the catabolic reactions facilitating the retrieval of nutrients from the senescing leaf. We propose a model illustrating the specific metabolic strategies employed by leaves in response to these two darkening treatments, which support either rapid senescence or a strong capacity for survival.

Keywords
Arabidopsis thaliana, senescence, metabolism, dark induced senescence, survival
National Category
Botany
Research subject
biology
Identifiers
urn:nbn:se:umu:diva-147675 (URN)10.1104/pp.18.00062 (DOI)000431347500015 ()29523713 (PubMedID)
Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-06-09Bibliographically approved
Keech, O., Gardeström, P., Kleczkowski, L. A. & Rouhier, N. (2017). The redox control of photorespiration: from biochemical and physiological aspects to biotechnological considerations. Plant, Cell and Environment, 40(4), 553-569
Open this publication in new window or tab >>The redox control of photorespiration: from biochemical and physiological aspects to biotechnological considerations
2017 (English)In: Plant, Cell and Environment, ISSN 0140-7791, E-ISSN 1365-3040, Vol. 40, no 4, p. 553-569Article, review/survey (Refereed) Published
Abstract [en]

Photorespiration is a complex and tightly regulated process occurring in photosynthetic organisms. This process can alter the cellular redox balance, notably via the production and consumption of both reducing and oxidizing equivalents. Under certain circumstances, these equivalents, as well as reactive oxygen or nitrogen species, can become prominent in subcellular compartments involved in the photorespiratory process, eventually promoting oxidative post-translational modifications of proteins. Keeping these changes under tight control should therefore be of primary importance. In order to review the current state of knowledge about the redox control of photorespiration, we primarily performed a careful description of the known and potential redox-regulated or oxidation sensitive photorespiratory proteins, and examined in more details two interesting cases: the glycerate kinase and the glycine cleavage system. When possible, the potential impact and subsequent physiological regulations associated with these changes have been discussed. In a second part, we reviewed the extent to which photorespiration contributes to cellular redox homeostasis considering, in particular, the set of peripheral enzymes associated with the canonical photorespiratory pathway. Finally, some recent biotechnological strategies to circumvent photorespiration for future growth improvements are discussed in the light of these redox regulations.

Keywords
cysteine, photorespiration, post-translational regulation, redox proteomics, reducing equivalent
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-118759 (URN)10.1111/pce.12713 (DOI)000397504400009 ()26791824 (PubMedID)
Available from: 2016-04-04 Created: 2016-04-04 Last updated: 2018-06-07Bibliographically approved
Liebsch, D. & Keech, O. (2016). Dark-induced leaf senescence: new insights into a complex light-dependent regulatory pathway. New Phytologist, 212(3), 563-570
Open this publication in new window or tab >>Dark-induced leaf senescence: new insights into a complex light-dependent regulatory pathway
2016 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 212, no 3, p. 563-570Article, review/survey (Refereed) Published
Abstract [en]

Leaf senescence - the coordinated, active process leading to the organized dismantling of cellular components to remobilize resources - is a fundamental aspect of plant life. Its tight regulation is essential for plant fitness and has crucial implications for the optimization of plant productivity and storage properties. Various investigations have shown light deprivation and light perception via phytochromes as key elements modulating senescence. However, the signalling pathways linking light deprivation and actual senescence processes have long remained obscure. Recent analyses have demonstrated that PHYTOCHROME-INTERACTING FACTORS (PIFs) are major transcription factors orchestrating dark-induced senescence (DIS) by targeting chloroplast maintenance, chlorophyll metabolism, hormone signalling and production, and the expression of senescence master regulators, uncovering potential molecular links to the energy deprivation signalling pathway. PIF-dependent feed-forward regulatory modules might be of critical importance for the highly complex and initially light-reversible DIS induction.

Keywords
carbon starvation, dark, phytochrome, PHYTOCHROME-INTERACTING FACTOR (PIF), senescence, shade, signalling
National Category
Plant Biotechnology Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-127593 (URN)10.1111/nph.14217 (DOI)000385797800006 ()27716940 (PubMedID)
Available from: 2016-12-09 Created: 2016-11-16 Last updated: 2018-06-09Bibliographically approved
Chrobok, D., Law, S. R., Brouwer, B., Linden, P., Ziolkowska, A., Liebsch, D., . . . Keech, O. (2016). Dissecting the Metabolic Role of Mitochondria during Developmental Leaf Senescence. Plant Physiology, 172(4), 2132-2153
Open this publication in new window or tab >>Dissecting the Metabolic Role of Mitochondria during Developmental Leaf Senescence
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2016 (English)In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 172, no 4, p. 2132-2153Article in journal (Refereed) Published
Abstract [en]

The functions of mitochondria during leaf senescence, a type of programmed cell death aimed at the massive retrieval of nutrients from the senescing organ to the rest of the plant, remain elusive. Here, combining experimental and analytical approaches, we showed that mitochondrial integrity in Arabidopsis (Arabidopsis thaliana) is conserved until the latest stages of leaf senescence, while their number drops by 30%. Adenylate phosphorylation state assays and mitochondrial respiratory measurements indicated that the leaf energy status also is maintained during this time period. Furthermore, after establishing a curated list of genes coding for products targeted to mitochondria, we analyzed in isolation their transcript profiles, focusing on several key mitochondrial functions, such as the tricarboxylic acid cycle, mitochondrial electron transfer chain, iron-sulfur cluster biosynthesis, transporters, as well as catabolic pathways. In tandem with a metabolomic approach, our data indicated that mitochondrial metabolism was reorganized to support the selective catabolism of both amino acids and fatty acids. Such adjustments would ensure the replenishment of alpha-ketoglutarate and glutamate, which provide the carbon backbones for nitrogen remobilization. Glutamate, being the substrate of the strongly up-regulated cytosolic glutamine synthase, is likely to become a metabolically limiting factor in the latest stages of developmental leaf senescence. Finally, an evolutionary age analysis revealed that, while branched-chain amino acid and proline catabolism are very old mitochondrial functions particularly enriched at the latest stages of leaf senescence, auxin metabolism appears to be rather newly acquired. In summation, our work shows that, during developmental leaf senescence, mitochondria orchestrate catabolic processes by becoming increasingly central energy and metabolic hubs.

National Category
Botany
Identifiers
urn:nbn:se:umu:diva-131100 (URN)10.1104/pp.16.01463 (DOI)000391173400006 ()27744300 (PubMedID)
Available from: 2017-02-13 Created: 2017-02-13 Last updated: 2018-06-09Bibliographically approved
Betti, M., Bauwe, H., Busch, F. A., Fernie, A. R., Keech, O., Levey, M., . . . Weber, A. P. M. (2016). Manipulating photorespiration to increase plant productivity: recent advances and perspectives for crop improvement. Journal of Experimental Botany, 67(10), 2977-2988
Open this publication in new window or tab >>Manipulating photorespiration to increase plant productivity: recent advances and perspectives for crop improvement
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2016 (English)In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 67, no 10, p. 2977-2988Article, review/survey (Refereed) Published
Abstract [en]

Recycling of the 2-phosphoglycolate generated by the oxygenase reaction of Rubisco requires a complex and energy-consuming set of reactions collectively known as the photorespiratory cycle. Several approaches aimed at reducing the rates of photorespiratory energy or carbon loss have been proposed, based either on screening for natural variation or by means of genetic engineering. Recent work indicates that plant yield can be substantially improved by the alteration of photorespiratory fluxes or by engineering artificial bypasses to photorespiration. However, there is also evidence indicating that, under certain environmental and/or nutritional conditions, reduced photorespiratory capacity may be detrimental to plant performance. Here we summarize recent advances obtained in photorespiratory engineering and discuss prospects for these advances to be transferred to major crops to help address the globally increasing demand for food and biomass production.

Keywords
Crops, food production, genetic engineering, photorespiration, Rubisco, yield improvement
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-118761 (URN)10.1093/jxb/erw076 (DOI)000376658300008 ()26951371 (PubMedID)
Note

Special Issue: Photorespiration: Origins and Metabolic Integration in Interacting Compartments

Available from: 2016-04-04 Created: 2016-04-04 Last updated: 2018-06-07Bibliographically approved
Dejonghe, W., Kuenen, S., Mylle, E., Vasileva, M., Keech, O., Viotti, C., . . . Russinova, E. (2016). Mitochondrial uncouplers inhibit clathrin-mediated endocytosis largely through cytoplasmic acidification. Nature Communications, 7, Article ID 11710.
Open this publication in new window or tab >>Mitochondrial uncouplers inhibit clathrin-mediated endocytosis largely through cytoplasmic acidification
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2016 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 11710Article in journal (Refereed) Published
Abstract [en]

ATP production requires the establishment of an electrochemical proton gradient across the inner mitochondrial membrane. Mitochondrial uncouplers dissipate this proton gradient and disrupt numerous cellular processes, including vesicular trafficking, mainly through energy depletion. Here we show that Endosidin9 (ES9), a novel mitochondrial uncoupler, is a potent inhibitor of clathrin-mediated endocytosis (CME) in different systems and that ES9 induces inhibition of CME not because of its effect on cellular ATP, but rather due to its protonophore activity that leads to cytoplasm acidification. We show that the known tyrosine kinase inhibitor tyrphostinA23, which is routinely used to block CME, displays similar properties, thus questioning its use as a specific inhibitor of cargo recognition by the AP-2 adaptor complex via tyrosine motif-based endocytosis signals. Furthermore, we show that cytoplasm acidification dramatically affects the dynamics and recruitment of clathrin and associated adaptors, and leads to reduction of phosphatidylinositol 4,5-biphosphate from the plasma membrane.

National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:umu:diva-123991 (URN)10.1038/ncomms11710 (DOI)000377899800001 ()27271794 (PubMedID)
Available from: 2016-07-13 Created: 2016-07-07 Last updated: 2018-06-07Bibliographically approved
Hodges, M., Dellero, Y., Keech, O., Betti, M., Raghavendra, A. S., Sage, R., . . . Weber, A. P. M. (2016). Perspectives for a better understanding of the metabolic integration of photorespiration within a complex plant primary metabolism network. Journal of Experimental Botany, 67(10), 3015-3026
Open this publication in new window or tab >>Perspectives for a better understanding of the metabolic integration of photorespiration within a complex plant primary metabolism network
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2016 (English)In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 67, no 10, p. 3015-3026Article, review/survey (Refereed) Published
Abstract [en]

Recent advances in photorespiration research are described and future priorities to better understand the metabolic integration of the photorespiratory cycle within the complex network of plant primary metabolism are discussed.Photorespiration is an essential high flux metabolic pathway that is found in all oxygen-producing photosynthetic organisms. It is often viewed as a closed metabolic repair pathway that serves to detoxify 2-phosphoglycolic acid and to recycle carbon to fuel the Calvin-Benson cycle. However, this view is too simplistic since the photorespiratory cycle is known to interact with several primary metabolic pathways, including photosynthesis, nitrate assimilation, amino acid metabolism, C-1 metabolism and the Krebs (TCA) cycle. Here we will review recent advances in photorespiration research and discuss future priorities to better understand (i) the metabolic integration of the photorespiratory cycle within the complex network of plant primary metabolism and (ii) the importance of photorespiration in response to abiotic and biotic stresses.

Keywords
Biotic and abiotic stress, flux modeling, metabolic network, metabolic repair, photorespiration, regulation
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-122575 (URN)10.1093/jxb/erw145 (DOI)000376658300011 ()27053720 (PubMedID)
Note

Special Issue: Photorespiration: Origins and Metabolic Integration in Interacting Compartments

Available from: 2016-07-26 Created: 2016-06-20 Last updated: 2018-06-07Bibliographically approved
Lindén, P., Keech, O., Stenlund, H., Gardeström, P. & Moritz, T. (2016). Reduced mitochondrial malate dehydrogenase activity has a strong effect on photorespiratory metabolism as revealed by 13C labelling. Journal of Experimental Botany, 67(10), 3123-3135
Open this publication in new window or tab >>Reduced mitochondrial malate dehydrogenase activity has a strong effect on photorespiratory metabolism as revealed by 13C labelling
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2016 (English)In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 67, no 10, p. 3123-3135Article in journal (Refereed) Published
Abstract [en]

Mitochondrial malate dehydrogenase (mMDH) catalyses the interconversion of malate and oxaloacetate (OAA) in the tricarboxylic acid (TCA) cycle. Its activity is important for redox control of the mitochondrial matrix, through which it may participate in regulation of TCA cycle turnover. In Arabidopsis, there are two isoforms of mMDH. Here, we investigated to which extent the lack of the major isoform, mMDH1 accounting for about 60% of the activity, affected leaf metabolism. In air, rosettes of mmdh1 plants were only slightly smaller than wild type plants although the fresh weight was decreased by about 50%. In low CO2 the difference was much bigger, with mutant plants accumulating only 14% of fresh weight as compared to wild type. To investigate the metabolic background to the differences in growth, we developed a 13CO2 labelling method, using a custom-built chamber that enabled simultaneous treatment of sets of plants under controlled conditions. The metabolic profiles were analysed by gas- and liquid- chromatography coupled to mass spectrometry to investigate the metabolic adjustments between wild type and mmdh1. The genotypes responded similarly to high CO2 treatment both with respect to metabolite pools and 13C incorporation during a 2-h treatment. However, under low CO2 several metabolites differed between the two genotypes and, interestingly most of these were closely associated with photorespiration. We found that while the glycine/serine ratio increased, a concomitant altered glutamine/glutamate/α-ketoglutarate relation occurred. Taken together, our results indicate that adequate mMDH activity is essential to shuttle reductants out from the mitochondria to support the photorespiratory flux, and strengthen the idea that photorespiration is tightly intertwined with peripheral metabolic reactions.

Keywords
Heavy isotope labelling, mass spectrometry, mitochondrial malate dehydrogenase, photorespiration, primary carbon metabolism, redox balance
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-118760 (URN)10.1093/jxb/erw030 (DOI)000376658300019 ()26889011 (PubMedID)
Note

Special issue: Photorespiration: Origins and Metabolic Integration in Interacting Compartments

Available from: 2016-04-04 Created: 2016-04-04 Last updated: 2018-06-07Bibliographically approved
Brouwer, B., Gardeström, P. & Keech, O. (2014). In response to partial plant shading, the lack of phytochrome A does not directly induce leaf senescence but alters the fine-tuning of chlorophyll biosynthesis. Journal of Experimental Botany, 65(14), 4037-4049
Open this publication in new window or tab >>In response to partial plant shading, the lack of phytochrome A does not directly induce leaf senescence but alters the fine-tuning of chlorophyll biosynthesis
2014 (English)In: Journal of Experimental Botany, ISSN 0022-0957, E-ISSN 1460-2431, Vol. 65, no 14, p. 4037-4049Article in journal (Refereed) Published
Abstract [en]

Phytochrome is thought to control the induction of leaf senescence directly, however, the signalling and molecular mechanisms remain unclear. In the present study, an ecophysiological approach was used to establish a functional connection between phytochrome signalling and the physiological processes underlying the induction of leaf senescence in response to shade. With shade it is important to distinguish between complete and partial shading, during which either the whole or only a part of the plant is shaded, respectively. It is first shown here that, while PHYB is required to maintain chlorophyll content in a completely shaded plant, only PHYA is involved in maintaining the leaf chlorophyll content in response to partial plant shading. Second, it is shown that leaf yellowing associated with strong partial shading in phyA-mutant plants actually correlates to a decreased biosynthesis of chlorophyll rather than to an increase of its degradation. Third, it is shown that the physiological impact of this decreased biosynthesis of chlorophyll in strongly shaded phyA-mutant leaves is accompanied by a decreased capacity to adjust the Light Compensation Point. However, the increased leaf yellowing in phyA-mutant plants is not accompanied by an increase of senescence-specific molecular markers, which argues against a direct role of PHYA in inducing leaf senescence in response to partial shade. In conclusion, it is proposed that PHYA, but not PHYB, is essential for fine-tuning the chlorophyll biosynthetic pathway in response to partial shading. In turn, this mechanism allows the shaded leaf to adjust its photosynthetic machinery to very low irradiances, thus maintaining a positive carbon balance and repressing the induction of leaf senescence, which can occur under prolonged periods of shade.

Place, publisher, year, edition, pages
Oxford University Press, 2014
Keywords
Arabidopsis, chlorophyll, far-red light, phytochrome, senescence, shade
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-92956 (URN)10.1093/jxb/eru060 (DOI)000339954000020 ()
Available from: 2014-09-12 Created: 2014-09-09 Last updated: 2018-06-07Bibliographically approved
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