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Wieloch T, Sharkey TD, Werner RA, Schleucher J. Intramolecular carbon isotope signals reflect metabolite allocation in plants. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:2558-2575. [PMID: 35084456 PMCID: PMC9015809 DOI: 10.1093/jxb/erac028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 01/24/2022] [Indexed: 05/26/2023]
Abstract
Stable isotopes at natural abundance are key tools to study physiological processes occurring outside the temporal scope of manipulation and monitoring experiments. Whole-molecule carbon isotope ratios (13C/12C) enable assessments of plant carbon uptake yet conceal information about carbon allocation. Here, we identify an intramolecular 13C/12C signal at tree-ring glucose C-5 and C-6 and develop experimentally testable theories on its origin. More specifically, we assess the potential of processes within C3 metabolism for signal introduction based (inter alia) on constraints on signal propagation posed by metabolic networks. We propose that the intramolecular signal reports carbon allocation into major metabolic pathways in actively photosynthesizing leaf cells including the anaplerotic, shikimate, and non-mevalonate pathway. We support our theoretical framework by linking it to previously reported whole-molecule 13C/12C increases in cellulose of ozone-treated Betula pendula and a highly significant relationship between the intramolecular signal and tropospheric ozone concentration. Our theory postulates a pronounced preference for leaf cytosolic triose-phosphate isomerase to catalyse the forward reaction in vivo (dihydroxyacetone phosphate to glyceraldehyde 3-phosphate). In conclusion, intramolecular 13C/12C analysis resolves information about carbon uptake and allocation enabling more comprehensive assessments of carbon metabolism than whole-molecule 13C/12C analysis.
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Affiliation(s)
- Thomas Wieloch
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden
| | - Thomas David Sharkey
- MSU-DOE Plant Research Laboratory, Plant Resilience Institute, and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Roland Anton Werner
- Department of Environmental Systems Science, ETH Zürich, Universitätstrasse 2, 8092 Zürich, Switzerland
| | - Jürgen Schleucher
- Department of Medical Biochemistry and Biophysics, Umeå University, 901 87 Umeå, Sweden
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3
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Wieloch T, Sharkey TD. Compartment-specific energy requirements of photosynthetic carbon metabolism in Camelina sativa leaves. PLANTA 2022; 255:103. [PMID: 35415783 PMCID: PMC9005430 DOI: 10.1007/s00425-022-03884-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 03/25/2022] [Indexed: 06/14/2023]
Abstract
The oxidative pentose phosphate pathway provides cytosolic NADPH yet reduces carbon and energy use efficiency. Repressing this pathway and introducing cytosolic NADPH-dependent malate dehydrogenase may increase crop yields by ≈5%. Detailed knowledge about plant energy metabolism may aid crop improvements. Using published estimates of flux through central carbon metabolism, we phenotype energy metabolism in illuminated Camelina sativa leaves (grown at 22 °C, 500 µmol photons m-2 s-1) and report several findings. First, the oxidative pentose phosphate pathway (OPPP) transfers 3.3% of the NADPH consumed in the Calvin-Benson cycle to the cytosol. NADPH supply proceeds at about 10% of the rate of net carbon assimilation. However, concomitantly respired CO2 accounts for 4.8% of total rubisco activity. Hence, 4.8% of the flux through the Calvin-Benson cycle and photorespiration is spent on supplying cytosolic NADPH, a significant investment. Associated energy requirements exceed the energy output of the OPPP. Thus, autotrophic carbon metabolism is not simply optimised for flux into carbon sinks but sacrifices carbon and energy use efficiency to support cytosolic energy metabolism. To reduce these costs, we suggest bioengineering plants with a repressed cytosolic OPPP, and an inserted cytosolic NADPH-dependent malate dehydrogenase tuned to compensate for the loss in OPPP activity (if required). Second, sucrose cycling is a minor investment in overall leaf energy metabolism but a significant investment in cytosolic energy metabolism. Third, leaf energy balancing strictly requires oxidative phosphorylation, cofactor export from chloroplasts, and peroxisomal NADH import. Fourth, mitochondria are energetically self-sufficient. Fifth, carbon metabolism has an ATP/NADPH demand ratio of 1.52 which is met if ≤ 21.7% of whole electron flux is cyclic. Sixth, electron transport has a photon use efficiency of ≥ 62%. Last, we discuss interactions between the OPPP and the cytosolic oxidation-reduction cycle in supplying leaf cytosolic NADPH.
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Affiliation(s)
- Thomas Wieloch
- Department of Medical Biochemistry and Biophysics, KB. H6, Umeå University, 901 87, Umeå, Sweden.
| | - Thomas David Sharkey
- Department of Energy, Plant Research Laboratory, Michigan State University, East Lansing, MI, 48824, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA
- Plant Resilience Institute, Michigan State University, East Lansing, MI, 48824, USA
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Wieloch T, Grabner M, Augusti A, Serk H, Ehlers I, Yu J, Schleucher J. Metabolism is a major driver of hydrogen isotope fractionation recorded in tree-ring glucose of Pinus nigra. THE NEW PHYTOLOGIST 2022; 234:449-461. [PMID: 35114006 PMCID: PMC9306475 DOI: 10.1111/nph.18014] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 01/24/2022] [Indexed: 05/13/2023]
Abstract
Stable isotope abundances convey valuable information about plant physiological processes and underlying environmental controls. Central gaps in our mechanistic understanding of hydrogen isotope abundances impede their widespread application within the plant and biogeosciences. To address these gaps, we analysed intramolecular deuterium abundances in glucose of Pinus nigra extracted from an annually resolved tree-ring series (1961-1995). We found fractionation signals (i.e. temporal variability in deuterium abundance) at glucose H1 and H2 introduced by closely related metabolic processes. Regression analysis indicates that these signals (and thus metabolism) respond to drought and atmospheric CO2 concentration beyond a response change point. They explain ≈ 60% of the whole-molecule deuterium variability. Altered metabolism is associated with below-average yet not exceptionally low growth. We propose the signals are introduced at the leaf level by changes in sucrose-to-starch carbon partitioning and anaplerotic carbon flux into the Calvin-Benson cycle. In conclusion, metabolism can be the main driver of hydrogen isotope variation in plant glucose.
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Affiliation(s)
- Thomas Wieloch
- Department of Medical Biochemistry and BiophysicsUmeå University901 87UmeåSweden
| | - Michael Grabner
- Institute of Wood Technology and Renewable MaterialsUniversity of Natural Resources and Life Sciences Vienna3430Tulln an der DonauAustria
| | - Angela Augusti
- Research Institute on Terrestrial EcosystemsNational Research CouncilPorano (TR)05010Italy
| | - Henrik Serk
- Department of Medical Biochemistry and BiophysicsUmeå University901 87UmeåSweden
| | - Ina Ehlers
- Department of Medical Biochemistry and BiophysicsUmeå University901 87UmeåSweden
| | - Jun Yu
- Department of Mathematics and Mathematical StatisticsUmeå University901 87UmeåSweden
| | - Jürgen Schleucher
- Department of Medical Biochemistry and BiophysicsUmeå University901 87UmeåSweden
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Lima VF, Erban A, Daubermann AG, Freire FBS, Porto NP, Cândido-Sobrinho SA, Medeiros DB, Schwarzländer M, Fernie AR, Dos Anjos L, Kopka J, Daloso DM. Establishment of a GC-MS-based 13 C-positional isotopomer approach suitable for investigating metabolic fluxes in plant primary metabolism. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:1213-1233. [PMID: 34486764 DOI: 10.1111/tpj.15484] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 08/20/2021] [Accepted: 08/30/2021] [Indexed: 06/13/2023]
Abstract
13 C-Metabolic flux analysis (13 C-MFA) has greatly contributed to our understanding of plant metabolic regulation. However, the generation of detailed in vivo flux maps remains a major challenge. Flux investigations based on nuclear magnetic resonance have resolved small networks with high accuracy. Mass spectrometry (MS) approaches have broader potential, but have hitherto been limited in their power to deduce flux information due to lack of atomic level position information. Herein we established a gas chromatography (GC) coupled to MS-based approach that provides 13 C-positional labelling information in glucose, malate and glutamate (Glu). A map of electron impact (EI)-mediated MS fragmentation was created and validated by 13 C-positionally labelled references via GC-EI-MS and GC-atmospheric pressure chemical ionization-MS technologies. The power of the approach was revealed by analysing previous 13 C-MFA data from leaves and guard cells, and 13 C-HCO3 labelling of guard cells harvested in the dark and after the dark-to-light transition. We demonstrated that the approach is applicable to established GC-EI-MS-based 13 C-MFA without the need for experimental adjustment, but will benefit in the future from paired analyses by the two GC-MS platforms. We identified specific glucose carbon atoms that are preferentially labelled by photosynthesis and gluconeogenesis, and provide an approach to investigate the phosphoenolpyruvate carboxylase (PEPc)-derived 13 C-incorporation into malate and Glu. Our results suggest that gluconeogenesis and the PEPc-mediated CO2 assimilation into malate are activated in a light-independent manner in guard cells. We further highlight that the fluxes from glycolysis and PEPc toward Glu are restricted by the mitochondrial thioredoxin system in illuminated leaves.
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Affiliation(s)
- Valéria F Lima
- LabPLant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza-CE, 60451-970, Brazil
| | - Alexander Erban
- Max-Planck-Institute of Molecular Plant Physiology, Potsdam-Golm, D-14476, Germany
| | - André G Daubermann
- Departamento de Biologia, Setor de Fisiologia Vegetal, Universidade Federal de Lavras, Lavras-MG, 37200-900, Brazil
| | - Francisco Bruno S Freire
- LabPLant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza-CE, 60451-970, Brazil
| | - Nicole P Porto
- LabPLant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza-CE, 60451-970, Brazil
| | - Silvio A Cândido-Sobrinho
- LabPLant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza-CE, 60451-970, Brazil
| | - David B Medeiros
- Max-Planck-Institute of Molecular Plant Physiology, Potsdam-Golm, D-14476, Germany
| | - Markus Schwarzländer
- Institute of Plant Biology and Biotechnology, Westfälische-Wilhelms-Universität Münster, Münster, D-48143, Germany
| | - Alisdair R Fernie
- Max-Planck-Institute of Molecular Plant Physiology, Potsdam-Golm, D-14476, Germany
| | - Leticia Dos Anjos
- Departamento de Biologia, Setor de Fisiologia Vegetal, Universidade Federal de Lavras, Lavras-MG, 37200-900, Brazil
| | - Joachim Kopka
- Max-Planck-Institute of Molecular Plant Physiology, Potsdam-Golm, D-14476, Germany
| | - Danilo M Daloso
- LabPLant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza-CE, 60451-970, Brazil
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