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Dellero Y, Berardocco S, Bouchereau A. U- 13C-glucose incorporation into source leaves of Brassica napus highlights light-dependent regulations of metabolic fluxes within central carbon metabolism. JOURNAL OF PLANT PHYSIOLOGY 2024; 292:154162. [PMID: 38103478 DOI: 10.1016/j.jplph.2023.154162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 11/07/2023] [Accepted: 12/08/2023] [Indexed: 12/19/2023]
Abstract
Plant central carbon metabolism comprises several important metabolic pathways acting together to support plant growth and yield establishment. Despite the emergence of 13C-based dynamic approaches, the regulation of metabolic fluxes between light and dark conditions has not yet received sufficient attention for agronomically relevant plants. Here, we investigated the impact of light/dark conditions on carbon allocation processes within central carbon metabolism of Brassica napus after U-13C-glucose incorporation into leaf discs. Leaf gas-exchanges and metabolite contents were weakly impacted by the leaf disc method and the incorporation of glucose. 13C-analysis by GC-MS showed that U-13C-glucose was converted to fructose for de novo biosynthesis of sucrose at similar rates in both light and dark conditions. However, light conditions led to a reduced commitment of glycolytic carbons towards respiratory substrates (pyruvate, alanine, malate) and TCA cycle intermediates compared to dark conditions. Analysis of 13C-enrichment at the isotopologue level and metabolic pathway isotopic tracing reconstructions identified the contribution of multiple pathways to serine biosynthesis in light and dark conditions. However, the direct contribution of the glucose-6-phosphate shunt to serine biosynthesis was not observed. Our results also provided isotopic evidences for an active metabolic connection between the TCA cycle, glycolysis and photorespiration in light conditions through a rapid reallocation of TCA cycle decarboxylations back to the TCA cycle through photorespiration and glycolysis. Altogether, these results suggest the active coordination of core metabolic pathways across multiple compartments to reorganize C-flux modes.
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Affiliation(s)
- Younès Dellero
- INRAE, Université Rennes, Institut Agro, IGEPP-UMR1349, P2M2-MetaboHUB, Le Rheu, 35653, France.
| | - Solenne Berardocco
- INRAE, Université Rennes, Institut Agro, IGEPP-UMR1349, P2M2-MetaboHUB, Le Rheu, 35653, France
| | - Alain Bouchereau
- INRAE, Université Rennes, Institut Agro, IGEPP-UMR1349, P2M2-MetaboHUB, Le Rheu, 35653, France
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Lima VF, Freire FBS, Cândido-Sobrinho SA, Porto NP, Medeiros DB, Erban A, Kopka J, Schwarzländer M, Fernie AR, Daloso DM. Unveiling the dark side of guard cell metabolism. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2023; 201:107862. [PMID: 37413941 DOI: 10.1016/j.plaphy.2023.107862] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Revised: 06/02/2023] [Accepted: 06/22/2023] [Indexed: 07/08/2023]
Abstract
Evidence suggests that guard cells have higher rate of phosphoenolpyruvate carboxylase (PEPc)-mediated dark CO2 assimilation than mesophyll cells. However, it is unknown which metabolic pathways are activated following dark CO2 assimilation in guard cells. Furthermore, it remains unclear how the metabolic fluxes throughout the tricarboxylic acid (TCA) cycle and associated pathways are regulated in illuminated guard cells. Here we carried out a13C-HCO3 labelling experiment in tobacco guard cells harvested under continuous dark or during the dark-to-light transition to elucidate principles of metabolic dynamics downstream of CO2 assimilation. Most metabolic changes were similar between dark-exposed and illuminated guard cells. However, illumination altered the metabolic network structure of guard cells and increased the 13C-enrichment in sugars and metabolites associated to the TCA cycle. Sucrose was labelled in the dark, but light exposure increased the 13C-labelling and leads to more drastic reductions in the content of this metabolite. Fumarate was strongly labelled under both dark and light conditions, while illumination increased the 13C-enrichment in pyruvate, succinate and glutamate. Only one 13C was incorporated into malate and citrate in either dark or light conditions. Our results indicate that several metabolic pathways are redirected following PEPc-mediated CO2 assimilation in the dark, including gluconeogenesis and the TCA cycle. We further showed that the PEPc-mediated CO2 assimilation provides carbons for gluconeogenesis, the TCA cycle and glutamate synthesis and that previously stored malate and citrate are used to underpin the specific metabolic requirements of illuminated guard cells.
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Affiliation(s)
- Valéria F Lima
- LabPlant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, 60451-970, Fortaleza, Ceará, Brazil
| | - Francisco Bruno S Freire
- LabPlant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, 60451-970, Fortaleza, Ceará, Brazil
| | - Silvio A Cândido-Sobrinho
- LabPlant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, 60451-970, Fortaleza, Ceará, Brazil
| | - Nicole P Porto
- LabPlant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, 60451-970, Fortaleza, Ceará, Brazil
| | - David B Medeiros
- Max-Planck-Institute of Molecular Plant Physiology, 14476, Potsdam-Golm, Germany
| | - Alexander Erban
- Max-Planck-Institute of Molecular Plant Physiology, 14476, Potsdam-Golm, Germany
| | - Joachim Kopka
- Max-Planck-Institute of Molecular Plant Physiology, 14476, Potsdam-Golm, Germany
| | - Markus Schwarzländer
- Institute of Plant Biology and Biotechnology, Westfälische-Wilhelms-Universität Münster, D-48143, Münster, Germany
| | - Alisdair R Fernie
- Max-Planck-Institute of Molecular Plant Physiology, 14476, Potsdam-Golm, Germany
| | - Danilo M Daloso
- LabPlant, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, 60451-970, Fortaleza, Ceará, Brazil.
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Dellero Y, Filangi O, Bouchereau A. Evaluation of GC/MS-Based 13C-Positional Approaches for TMS Derivatives of Organic and Amino Acids and Application to Plant 13C-Labeled Experiments. Metabolites 2023; 13:metabo13040466. [PMID: 37110124 PMCID: PMC10142191 DOI: 10.3390/metabo13040466] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/20/2023] [Accepted: 03/20/2023] [Indexed: 04/29/2023] Open
Abstract
Analysis of plant metabolite 13C-enrichments with gas-chromatography mass spectrometry (GC/MS) has gained interest recently. By combining multiple fragments of a trimethylsilyl (TMS) derivative, 13C-positional enrichments can be calculated. However, this new approach may suffer from analytical biases depending on the fragments selected for calculation leading to significant errors in the final results. The goal of this study was to provide a framework for the validation of 13C-positional approaches and their application to plants based on some key metabolites (glycine, serine, glutamate, proline, α-alanine and malate). For this purpose, we used tailor-made 13C-PT standards, harboring known carbon isotopologue distributions and 13C-positional enrichments, to evaluate the reliability of GC-MS measurements and positional calculations. Overall, we showed that some mass fragments of proline_2TMS, glutamate_3TMS, malate_3TMS and α-alanine_2TMS had important biases for 13C measurements resulting in significant errors in the computational estimation of 13C-positional enrichments. Nevertheless, we validated a GC/MS-based 13C-positional approach for the following atomic positions: (i) C1 and C2 of glycine_3TMS, (ii) C1, C2 and C3 of serine_3TMS, and (iii) C1 of malate_3TMS and glutamate_3TMS. We successfully applied this approach to plant 13C-labeled experiments for investigating key metabolic fluxes of plant primary metabolism (photorespiration, tricarboxylic acid cycle and phosphoenolpyruvate carboxylase activity).
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Affiliation(s)
- Younès Dellero
- Institute for Genetics, Environment and Plant Protection (IGEPP), National Research Institute for Agriculture, Food and Environment (INRAE), Institut Agro, Université Rennes, 35650 Le Rheu, France
- Metabolic Profiling and Metabolomic Platform (P2M2), Biopolymers Interactions Assemblies, Institute for Genetics, Environment and Plant Protection, 35650 Le Rheu, France
- MetaboHUB, National Infrastructure of Metabolomics and Fluxomics, 35650 Le Rheu, France
| | - Olivier Filangi
- Institute for Genetics, Environment and Plant Protection (IGEPP), National Research Institute for Agriculture, Food and Environment (INRAE), Institut Agro, Université Rennes, 35650 Le Rheu, France
- Metabolic Profiling and Metabolomic Platform (P2M2), Biopolymers Interactions Assemblies, Institute for Genetics, Environment and Plant Protection, 35650 Le Rheu, France
- MetaboHUB, National Infrastructure of Metabolomics and Fluxomics, 35650 Le Rheu, France
| | - Alain Bouchereau
- Institute for Genetics, Environment and Plant Protection (IGEPP), National Research Institute for Agriculture, Food and Environment (INRAE), Institut Agro, Université Rennes, 35650 Le Rheu, France
- Metabolic Profiling and Metabolomic Platform (P2M2), Biopolymers Interactions Assemblies, Institute for Genetics, Environment and Plant Protection, 35650 Le Rheu, France
- MetaboHUB, National Infrastructure of Metabolomics and Fluxomics, 35650 Le Rheu, France
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