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Yamada K, Mine A. Sugar coordinates plant defense signaling. SCIENCE ADVANCES 2024; 10:eadk4131. [PMID: 38266087 PMCID: PMC10807812 DOI: 10.1126/sciadv.adk4131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2023] [Accepted: 12/22/2023] [Indexed: 01/26/2024]
Abstract
Pathogen recognition triggers energy-intensive defense systems. Although successful defense should depend on energy availability, how metabolic information is communicated to defense remains unclear. We show that sugar, especially glucose-6-phosphate (G6P), is critical in coordinating defense in Arabidopsis. Under sugar-sufficient conditions, phosphorylation levels of calcium-dependent protein kinase 5 (CPK5) are elevated by G6P-mediated suppression of protein phosphatases, enhancing defense responses before pathogen invasion. Subsequently, recognition of bacterial flagellin activates sugar transporters, leading to increased cellular G6P, which elicits CPK5-independent signaling promoting synthesis of the phytohormone salicylic acid (SA) for antibacterial defense. In contrast, while perception of fungal chitin does not promote sugar influx or SA accumulation, chitin-induced synthesis of the antifungal compound camalexin requires basal sugar influx activity. By monitoring sugar levels, plants determine defense levels and execute appropriate outputs against bacterial and fungal pathogens. Together, our findings provide a comprehensive view of the roles of sugar in defense.
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Affiliation(s)
- Kohji Yamada
- Graduate School of Technology, Industrial and Social Sciences, Tokushima University, Tokushima, Japan
- JST, PRESTO, Kawaguchi, Japan
| | - Akira Mine
- JST, PRESTO, Kawaguchi, Japan
- Graduate School of Agriculture, Kyoto University, Kyoto, Japan
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2
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Wieloch T, Augusti A, Schleucher J. Anaplerotic flux into the Calvin-Benson cycle: hydrogen isotope evidence for in vivo occurrence in C 3 metabolism. THE NEW PHYTOLOGIST 2022; 234:405-411. [PMID: 35020197 PMCID: PMC9305100 DOI: 10.1111/nph.17957] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 12/22/2021] [Indexed: 05/02/2023]
Abstract
As the central carbon uptake pathway in photosynthetic cells, the Calvin-Benson cycle is among the most important biochemical cycles for life on Earth. A carbon flux of anaplerotic origin (i.e. through the chloroplast-localized oxidative branch of the pentose phosphate pathway) into the Calvin-Benson cycle was proposed recently. Here, we measured intramolecular deuterium abundances in leaf starch of Helianthus annuus grown at varying ambient CO2 concentrations, Ca . Additionally, we modelled deuterium fractionations expected for the anaplerotic pathway and compared modelled with measured fractionations. We report deuterium fractionation signals at H1 and H2 of starch glucose. Below a Ca change point, these signals increase with decreasing Ca consistent with modelled fractionations by anaplerotic flux. Under standard conditions (Ca = 450 ppm corresponding to intercellular CO2 concentrations, Ci , of 328 ppm), we estimate negligible anaplerotic flux. At Ca = 180 ppm (Ci = 140 ppm), more than 10% of the glucose-6-phosphate entering the starch biosynthesis pathway is diverted into the anaplerotic pathway. In conclusion, we report evidence consistent with anaplerotic carbon flux into the Calvin-Benson cycle in vivo. We propose the flux may help to: maintain high levels of ribulose 1,5-bisphosphate under source-limited growth conditions to facilitate photorespiratory nitrogen assimilation required to build-up source strength; and counteract oxidative stress.
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Affiliation(s)
- Thomas Wieloch
- Department of Medical Biochemistry and BiophysicsUmeå UniversityUmeå90187Sweden
| | - Angela Augusti
- Research Institute on Terrestrial EcosystemsNational Research CouncilPorano (TR)05010Italy
| | - Jürgen Schleucher
- Department of Medical Biochemistry and BiophysicsUmeå UniversityUmeå90187Sweden
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3
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Destailleur A, Poucet T, Cabasson C, Alonso AP, Cocuron JC, Larbat R, Vercambre G, Colombié S, Petriacq P, Andrieu MH, Beauvoit B, Gibon Y, Dieuaide-Noubhani M. The Evolution of Leaf Function during Development Is Reflected in Profound Changes in the Metabolic Composition of the Vacuole. Metabolites 2021; 11:metabo11120848. [PMID: 34940606 PMCID: PMC8707551 DOI: 10.3390/metabo11120848] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 11/30/2021] [Accepted: 12/02/2021] [Indexed: 11/16/2022] Open
Abstract
During its development, the leaf undergoes profound metabolic changes to ensure, among other things, its growth. The subcellular metabolome of tomato leaves was studied at four stages of leaf development, with a particular emphasis on the composition of the vacuole, a major actor of cell growth. For this, leaves were collected at different positions of the plant, corresponding to different developmental stages. Coupling cytology approaches to non-aqueous cell fractionation allowed to estimate the subcellular concentrations of major compounds in the leaves. The results showed major changes in the composition of the vacuole across leaf development. Thus, sucrose underwent a strong allocation, being mostly located in the vacuole at the beginning of development and in the cytosol at maturity. Furthermore, these analyses revealed that the vacuole, rather rich in secondary metabolites and sugars in the growth phases, accumulated organic acids thereafter. This result suggests that the maintenance of the osmolarity of the vacuole of mature leaves would largely involve inorganic molecules.
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Affiliation(s)
- Alice Destailleur
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
| | - Théo Poucet
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
| | - Cécile Cabasson
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
- Bordeaux Metabolome, MetaboHUB, PHENOME-EMPHASIS, F-33140 Villenave d’Ornon, France
| | - Ana Paula Alonso
- Department of Biological Sciences, BioDiscovery Institute, University of North Texas, Denton, TX 76203, USA;
| | | | - Romain Larbat
- LAE, Université de Lorraine, INRAE, F-54000 Nancy, France;
| | - Gilles Vercambre
- Plants and Cropping Systems in Horticulture, INRAE, F-84914 Avignon, France;
| | - Sophie Colombié
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
| | - Pierre Petriacq
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
- Bordeaux Metabolome, MetaboHUB, PHENOME-EMPHASIS, F-33140 Villenave d’Ornon, France
| | - Marie Hélène Andrieu
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
| | - Bertrand Beauvoit
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
| | - Yves Gibon
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
- Bordeaux Metabolome, MetaboHUB, PHENOME-EMPHASIS, F-33140 Villenave d’Ornon, France
| | - Martine Dieuaide-Noubhani
- UMR Biologie du Fruit et Pathologie, Université de Bordeaux, INRAE, F-33140 Villenave d’Ornon, France; (A.D.); (T.P.); (C.C.); (S.C.); (P.P.); (M.H.A.); (B.B.); (Y.G.)
- Correspondence:
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Zhao HL, Chang TG, Xiao Y, Zhu XG. Potential metabolic mechanisms for inhibited chloroplast nitrogen assimilation under high CO2. PLANT PHYSIOLOGY 2021; 187:1812-1833. [PMID: 34618071 PMCID: PMC8566258 DOI: 10.1093/plphys/kiab345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 06/28/2021] [Indexed: 05/31/2023]
Abstract
Improving photosynthesis is considered a major and feasible option to dramatically increase crop yield potential. Increased atmospheric CO2 concentration often stimulates both photosynthesis and crop yield, but decreases protein content in the main C3 cereal crops. This decreased protein content in crops constrains the benefits of elevated CO2 on crop yield and affects their nutritional value for humans. To support studies of photosynthetic nitrogen assimilation and its complex interaction with photosynthetic carbon metabolism for crop improvement, we developed a dynamic systems model of plant primary metabolism, which includes the Calvin-Benson cycle, the photorespiration pathway, starch synthesis, glycolysis-gluconeogenesis, the tricarboxylic acid cycle, and chloroplastic nitrogen assimilation. This model successfully captures responses of net photosynthetic CO2 uptake rate (A), respiration rate, and nitrogen assimilation rate to different irradiance and CO2 levels. We then used this model to predict inhibition of nitrogen assimilation under elevated CO2. The potential mechanisms underlying inhibited nitrogen assimilation under elevated CO2 were further explored with this model. Simulations suggest that enhancing the supply of α-ketoglutarate is a potential strategy to maintain high rates of nitrogen assimilation under elevated CO2. This model can be used as a heuristic tool to support research on interactions between photosynthesis, respiration, and nitrogen assimilation. It also provides a basic framework to support the design and engineering of C3 plant primary metabolism for enhanced photosynthetic efficiency and nitrogen assimilation in the coming high-CO2 world.
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Affiliation(s)
- Hong-Long Zhao
- University of Chinese Academy of Sciences, Beijing 100049, China
- National Key Laboratory for Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Tian-Gen Chang
- National Key Laboratory for Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yi Xiao
- National Key Laboratory for Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200031, China
- Department of Crop Sciences, University of Illinois at Urbana Champaign, Urbana, Illinois 61801, USA
- Department of Plant Biology, University of Illinois at Urbana Champaign, Urbana, Illinois 61801, USA
| | - Xin-Guang Zhu
- National Key Laboratory for Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200031, China
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Voitsekhovskaja OV, Melnikova AN, Demchenko KN, Ivanova AN, Dmitrieva VA, Maksimova AI, Lohaus G, Tomos AD, Tyutereva EV, Koroleva OA. Leaf Epidermis: The Ambiguous Symplastic Domain. FRONTIERS IN PLANT SCIENCE 2021; 12:695415. [PMID: 34394148 PMCID: PMC8358407 DOI: 10.3389/fpls.2021.695415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 06/24/2021] [Indexed: 06/13/2023]
Abstract
The ability to develop secondary (post-cytokinetic) plasmodesmata (PD) is an important evolutionary advantage that helps in creating symplastic domains within the plant body. Developmental regulation of secondary PD formation is not completely understood. In flowering plants, secondary PD occur exclusively between cells from different lineages, e.g., at the L1/L2 interface within shoot apices, or between leaf epidermis (L1-derivative), and mesophyll (L2-derivative). However, the highest numbers of secondary PD occur in the minor veins of leaf between bundle sheath cells and phloem companion cells in a group of plant species designated "symplastic" phloem loaders, as opposed to "apoplastic" loaders. This poses a question of whether secondary PD formation is upregulated in general in symplastic loaders. Distribution of PD in leaves and in shoot apices of two symplastic phloem loaders, Alonsoa meridionalis and Asarina barclaiana, was compared with that in two apoplastic loaders, Solanum tuberosum (potato) and Hordeum vulgare (barley), using immunolabeling of the PD-specific proteins and transmission electron microscopy (TEM), respectively. Single-cell sampling was performed to correlate sugar allocation between leaf epidermis and mesophyll to PD abundance. Although the distribution of PD in the leaf lamina (except within the vascular tissues) and in the meristem layers was similar in all species examined, far fewer PD were found at the epidermis/epidermis and mesophyll/epidermis boundaries in apoplastic loaders compared to symplastic loaders. In the latter, the leaf epidermis accumulated sugar, suggesting sugar import from the mesophyll via PD. Thus, leaf epidermis and mesophyll might represent a single symplastic domain in Alonsoa meridionalis and Asarina barclaiana.
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Affiliation(s)
- Olga V. Voitsekhovskaja
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
- Department of Plant Biochemistry, Albrecht von Haller Institute for Plant Sciences, Göttingen, Germany
| | - Anna N. Melnikova
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
- Saint Petersburg State University, Saint Petersburg, Russia
| | - Kirill N. Demchenko
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Alexandra N. Ivanova
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
- Saint Petersburg State University, Saint Petersburg, Russia
| | - Valeria A. Dmitrieva
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
| | | | - Gertrud Lohaus
- Department of Plant Biochemistry, Albrecht von Haller Institute for Plant Sciences, Göttingen, Germany
- Molecular Plant Research/Plant Biochemistry, School of Mathematics and Natural Sciences, University of Wuppertal, Wuppertal, Germany
| | - A. Deri Tomos
- School of Biological Sciences, Bangor University, Bangor, United Kingdom
| | - Elena V. Tyutereva
- Komarov Botanical Institute, Russian Academy of Sciences, Saint Petersburg, Russia
| | - Olga A. Koroleva
- School of Biological Sciences, Bangor University, Bangor, United Kingdom
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van den Herik B, Bergonzi S, Bachem CWB, ten Tusscher K. Modelling the physiological relevance of sucrose export repression by an Flowering Time homolog in the long-distance phloem of potato. PLANT, CELL & ENVIRONMENT 2021; 44:792-806. [PMID: 33314152 PMCID: PMC7986384 DOI: 10.1111/pce.13977] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 12/03/2020] [Accepted: 12/03/2020] [Indexed: 05/31/2023]
Abstract
Yield of harvestable plant organs depends on photosynthetic assimilate production in source leaves, long-distance sucrose transport and sink-strength. While photosynthesis optimization has received considerable interest for optimizing plant yield, the potential for improving long-distance sucrose transport has received far less attention. Interestingly, a recent potato study demonstrates that the tuberigen StSP6A binds to and reduces activity of the StSWEET11 sucrose exporter. While the study suggested that reducing phloem sucrose efflux may enhance tuber yield, the precise mechanism and physiological relevance of this effect remained an open question. Here, we develop the first mechanistic model for sucrose transport, parameterized for potato plants. The model incorporates SWEET-mediated sucrose export, SUT-mediated sucrose retrieval from the apoplast and StSP6A-StSWEET11 interactions. Using this model, we were able to substantiate the physiological relevance of the StSP6A-StSWEET11 interaction in the long-distance phloem for potato tuber yield, as well as to show the non-linear nature of this effect.
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Affiliation(s)
- Bas van den Herik
- Computational Developmental BiologyUtrecht UniversityUtrechtThe Netherlands
| | - Sara Bergonzi
- Plant BreedingWageningen University & ResearchWageningenThe Netherlands
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Keller I, Rodrigues CM, Neuhaus HE, Pommerrenig B. Improved resource allocation and stabilization of yield under abiotic stress. JOURNAL OF PLANT PHYSIOLOGY 2021; 257:153336. [PMID: 33360492 DOI: 10.1016/j.jplph.2020.153336] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 12/01/2020] [Accepted: 12/02/2020] [Indexed: 06/12/2023]
Abstract
Sugars are the main building blocks for carbohydrate storage, but also serve as signaling molecules and protective compounds during abiotic stress responses. Accordingly, sugar transport proteins fulfill multiple roles as they mediate long distance sugar allocation, but also shape the subcellular and tissue-specific carbohydrate profiles by balancing the levels of these molecules in various compartments. Accordingly, transporter activity represents a target by classical or directed breeding approaches, to either, directly increase phloem loading or to increase sink strength in crop species. The relative subcellular distribution of sugars is critical for molecular signaling affecting yield-relevant processes like photosynthesis, onset of flowering and stress responses, while controlled long-distance sugar transport directly impacts development and productivity of plants. However, long-distance transport is prone to become unbalanced upon adverse environmental conditions. Therefore, we highlight the influence of stress stimuli on sucrose transport in the phloem and include the role of stress induced cellular carbohydrate sinks, like raffinose or fructans, which possess important roles to build up tolerance against challenging environmental conditions. In addition, we report on recent breeding approaches that resulted in altered source and sink capacities, leading to increased phloem sucrose shuttling in crops. Finally, we present strategies integrating the need of cellular stress-protection into the general picture of long-distance transport under abiotic stress, and point to possible approaches improving plant performance and resource allocation under adverse environmental conditions, leading to stabilized or even increased crop yield.
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Affiliation(s)
- Isabel Keller
- Plant Physiology, University of Kaiserslautern, Kaiserslautern, Germany
| | | | - H Ekkehard Neuhaus
- Plant Physiology, University of Kaiserslautern, Kaiserslautern, Germany.
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Measurement of Subcellular Metabolite Concentrations in Relation to Phloem Loading. Methods Mol Biol 2020; 2014:235-251. [PMID: 31197801 DOI: 10.1007/978-1-4939-9562-2_20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The key step of carbon export from green leaves is the loading of sugars into the phloem. To fully understand and quantify this process, it is essential to know the concentration of sugars in the different compartments of the cells along the phloem loading pathway. However, determining subcellular metabolite concentrations has been technically challenging. This paper describes a technique to measure metabolite levels in the chloroplast, the cytosol, and the vacuole of mesophyll cells with high accuracy. The nonaqueous fractionation (NAF) technique is arguably the method of choice to analyze the subcellular metabolite distributions as it minimizes the risk of metabolite interconversions or redistribution during the process. The principle of NAF is the separation of small subcellular particles, which are obtained by homogenization, lyophilization, and sonication, in a nonaqueous density gradient. Due to the varying composition-dependent density of the fragments, their segregation reflects compartmental distributions throughout the gradient. By determining marker enzymes for chloroplast stroma, cytosol, and vacuole in gradient fractions the proportions of each subcellular compartment in each gradient fraction can be analyzed. The measured distribution of marker enzymes and of metabolites in each fraction of the gradient can be used to calculate the subcellular distribution of the metabolites.
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Schneider S, Harant D, Bachmann G, Nägele T, Lang I, Wienkoop S. Subcellular Phenotyping: Using Proteomics to Quantitatively Link Subcellular Leaf Protein and Organelle Distribution Analyses of Pisum sativum Cultivars. FRONTIERS IN PLANT SCIENCE 2019; 10:638. [PMID: 31191569 PMCID: PMC6534152 DOI: 10.3389/fpls.2019.00638] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 04/29/2019] [Indexed: 06/09/2023]
Abstract
Plant phenotyping to date typically comprises morphological and physiological profiling in a high-throughput manner. A powerful method that allows for subcellular characterization of organelle stoichiometric/functional characteristics is still missing. Organelle abundance and crosstalk in cell dynamics and signaling plays an important role for understanding crop growth and stress adaptations. However, microscopy cannot be considered a high-throughput technology. The aim of the present study was to develop an approach that enables the estimation of organelle functional stoichiometry and to determine differential subcellular dynamics within and across cultivars in a high-throughput manner. A combination of subcellular non-aqueous fractionation and liquid chromatography mass spectrometry was applied to assign membrane-marker proteins to cell compartmental abundances and functions of Pisum sativum leaves. Based on specific subcellular affiliation, proteotypic marker peptides of the chloroplast, mitochondria and vacuole membranes were selected and synthesized as heavy isotope labeled standards. The rapid and unbiased Mass Western approach for accurate stoichiometry and targeted absolute protein quantification allowed for a proportional organelle abundances measure linked to their functional properties. A 3D Confocal Laser Scanning Microscopy approach was developed to evaluate the Mass Western. Two P. sativum cultivars of varying morphology and physiology were compared. The Mass Western assay enabled a cultivar specific discrimination of the chloroplast to mitochondria to vacuole relations.
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Affiliation(s)
- Sebastian Schneider
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
| | - Dominik Harant
- Core Facility Cell Imaging and Ultrastructure Research, University of Vienna, Vienna, Austria
| | - Gert Bachmann
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
| | - Thomas Nägele
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
- Department Biology I, Plant Evolutionary Cell Biology, Ludwig-Maximilians Universität, Munich, Germany
| | - Ingeborg Lang
- Core Facility Cell Imaging and Ultrastructure Research, University of Vienna, Vienna, Austria
| | - Stefanie Wienkoop
- Division of Molecular Systems Biology, Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, Austria
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Lothier J, De Paepe R, Tcherkez G. Mitochondrial complex I dysfunction increases CO 2 efflux and reconfigures metabolic fluxes of day respiration in tobacco leaves. THE NEW PHYTOLOGIST 2019; 221:750-763. [PMID: 30133747 DOI: 10.1111/nph.15393] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2018] [Accepted: 07/15/2018] [Indexed: 06/08/2023]
Abstract
Mutants affected in complex I are useful to understand the role played by mitochondrial electron transport and redox metabolism in cellular homeostasis and signaling. However, their respiratory phenotype is incompletely described and a specific examination of day respiration (Rd ) is lacking. Here, we used isotopic methods and metabolomics to investigate the impact of complex I dysfunction on Rd in two respiratory mutants of forest tobacco (Nicotiana sylvestris): cytoplasmic male sterile II (CMSII) and nuclear male sterile 1 (NMS1), previously characterized for complex I disruption. Rd was higher in mutants and the inhibition of leaf respiration by light was lower. Higher Rd values were caused by increased (phosphoenol)pyruvate (PEP) metabolism at the expense of anaplerotic (PEP carboxylase (PEPc) -catalyzed) activity. De novo synthesis of Krebs cycle intermediates in the light was larger in mutants than in the wild-type, although numerically small in all genotypes. Carbon metabolism in mutants involved alternative pathways, such as alanine synthesis, and an increase in amino acid production with the notable exception of aspartate. Our results show that the alteration of NADH re-oxidation activity by complex I does not cause a general inhibition of catabolism, but rather a re-orchestration of fluxes in day respiratory metabolism, leading to an increased CO2 efflux.
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Affiliation(s)
- Jérémy Lothier
- Institut de Recherche en Horticulture et Semences, UMR 1345 INRA-Université d'Angers, 42 rue Georges Morel, 49071, Beaucouzé Cedex, France
| | - Rosine De Paepe
- Institute of Plant Sciences Paris-Saclay, UMR 9213/UMR1403, Université Paris Sud, CNRS-INRA, Université d'Evry, Université Paris-Diderot, Bâtiment 630, 91405, Orsay Cedex, France
| | - Guillaume Tcherkez
- Research School of Biology, Australian National University, ANU College of Science, 2601, Canberra, ACT, Australia
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Fink D, Dobbelstein E, Barbian A, Lohaus G. Ratio of sugar concentrations in the phloem sap and the cytosol of mesophyll cells in different tree species as an indicator of the phloem loading mechanism. PLANTA 2018; 248:661-673. [PMID: 29882156 DOI: 10.1007/s00425-018-2933-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 06/01/2018] [Indexed: 05/28/2023]
Abstract
Sucrose concentration in phloem sap was several times higher than in the cytosol of mesophyll cells. The results suggest that phloem loading involves active steps in the analyzed tree species. Phloem loading in source leaves is a key step for carbon partitioning and passive symplastic loading has been proposed for several tree species. However, experimental evidence to prove the potential for sucrose diffusion from mesophyll to phloem is rare. Here, we analyzed three tree species (two angiosperms, Fagus sylvatica, Magnolia kobus, and one gymnosperm, Gnetum gnemon) to investigate the proposed phloem loading mechanism. For this purpose, the minor vein structure and the sugar concentrations in phloem sap as well as in the subcellular compartments of mesophyll cells were investigated. The analyzed tree species belong to the open type minor vein subcategory. The sucrose concentration in the cytosol of mesophyll cells ranged between 75 and 165 mM and was almost equal to the vacuolar concentration. Phloem sap could be collected from F. sylvatica and M. kobus and the concentration of sucrose in phloem sap was about five- and 11-fold higher, respectively, than in the cytosol of mesophyll cells. Sugar exudation of cut leaves was decreased by p-chloromercuribenzenesulfonic acid, an inhibitor of sucrose-proton transporter. The results suggest that phloem loading of sucrose in the analyzed tree species involves active steps, and apoplastic phloem loading seems more likely.
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Affiliation(s)
- Daniel Fink
- Molecular Plant Science/Plant Biochemistry, University of Wuppertal, Wuppertal, Germany
| | - Elena Dobbelstein
- Molecular Plant Science/Plant Biochemistry, University of Wuppertal, Wuppertal, Germany
| | - Andreas Barbian
- Core Facility Electron Microscopy, UKD, Heinrich Heine University Düsseldorf, Düsseldorf, Germany
| | - Gertrud Lohaus
- Molecular Plant Science/Plant Biochemistry, University of Wuppertal, Wuppertal, Germany.
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Abstract
Dynamic systems modeling is a method to study systematic properties of a complex system. The basic principles, procedures, and tools available to develop a dynamic systems model of complex metabolic processes are detailed. Here, a photosynthetic carbon metabolism model, which includes the Calvin Benson cycle, photorespiration, and starch and sucrose synthesis pathways, is used as an example to illustrate the whole process of model development.
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Affiliation(s)
- Honglong Zhao
- Plant Systems Biology Group, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Fenglin Road 500, Shanghai, 200032, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yi Xiao
- Plant Systems Biology Group, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Fenglin Road 500, Shanghai, 200032, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xin-Guang Zhu
- Plant Systems Biology Group, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Fenglin Road 500, Shanghai, 200032, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
- Plant Systems Biology Groups, CAS Key Laboratory for Computational Biology, CAS-MPG Partner Institute for Computational Biology, CAS, Room 102, Physiology Building, Yueyang Road 320, Shanghai, 200031, China.
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Allwood JW, Chandra S, Xu Y, Dunn WB, Correa E, Hopkins L, Goodacre R, Tobin AK, Bowsher CG. Profiling of spatial metabolite distributions in wheat leaves under normal and nitrate limiting conditions. PHYTOCHEMISTRY 2015; 115:99-111. [PMID: 25680480 PMCID: PMC4518043 DOI: 10.1016/j.phytochem.2015.01.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 01/10/2015] [Accepted: 01/15/2015] [Indexed: 05/06/2023]
Abstract
The control and interaction between nitrogen and carbon assimilatory pathways is essential in both photosynthetic and non-photosynthetic tissue in order to support metabolic processes without compromising growth. Physiological differences between the basal and mature region of wheat (Triticum aestivum) primary leaves confirmed that there was a change from heterotrophic to autotrophic metabolism. Fourier Transform Infrared (FT-IR) spectroscopy confirmed the suitability and phenotypic reproducibility of the leaf growth conditions. Principal Component-Discriminant Function Analysis (PC-DFA) revealed distinct clustering between base, and tip sections of the developing wheat leaf, and from plants grown in the presence or absence of nitrate. Gas Chromatography-Time of Flight/Mass Spectrometry (GC-TOF/MS) combined with multivariate and univariate analyses, and Bayesian network (BN) analysis, distinguished different tissues and confirmed the physiological switch from high rates of respiration to photosynthesis along the leaf. The operation of nitrogen metabolism impacted on the levels and distribution of amino acids, organic acids and carbohydrates within the wheat leaf. In plants grown in the presence of nitrate there was reduced levels of a number of sugar metabolites in the leaf base and an increase in maltose levels, possibly reflecting an increase in starch turnover. The value of using this combined metabolomics analysis for further functional investigations in the future are discussed.
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Affiliation(s)
- J William Allwood
- School of Chemistry, Manchester Institute of Biotechnology, 131 Princess Street, Manchester M1 7DN, UK; School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Surya Chandra
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK
| | - Yun Xu
- School of Chemistry, Manchester Institute of Biotechnology, 131 Princess Street, Manchester M1 7DN, UK
| | - Warwick B Dunn
- School of Chemistry, Manchester Institute of Biotechnology, 131 Princess Street, Manchester M1 7DN, UK; Manchester Centre for Integrative Systems Biology, Manchester Institute of Biotechnology, 131 Princess Street, Manchester M1 7DN, UK; Centre for Advanced Discovery and Experimental Therapeutics (CADET), Central Manchester University Hospitals NHS Foundation Trust, York Place, Oxford Road, Manchester M13 9WL, UK; School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
| | - Elon Correa
- School of Chemistry, Manchester Institute of Biotechnology, 131 Princess Street, Manchester M1 7DN, UK
| | - Laura Hopkins
- School of Biology, Biomolecular Sciences Building, University of St Andrews, St Andrews, Fife, KY16 9ST Scotland, UK
| | - Royston Goodacre
- School of Chemistry, Manchester Institute of Biotechnology, 131 Princess Street, Manchester M1 7DN, UK; Manchester Centre for Integrative Systems Biology, Manchester Institute of Biotechnology, 131 Princess Street, Manchester M1 7DN, UK
| | - Alyson K Tobin
- Vice Chancellor's Office, York St John University, Lord Mayor's Walk, York YO31 7EX, UK
| | - Caroline G Bowsher
- Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PL, UK.
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14
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Suzuki Y, Fujimori T, Kanno K, Sasaki A, Ohashi Y, Makino A. Metabolome analysis of photosynthesis and the related primary metabolites in the leaves of transgenic rice plants with increased or decreased Rubisco content. PLANT, CELL & ENVIRONMENT 2012; 35:1369-79. [PMID: 22321318 DOI: 10.1111/j.1365-3040.2012.02494.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Because the comprehensive effects on metabolism by genetic manipulation of leaf Rubisco content are unknown, metabolome analysis was carried out on transgenic rice plants with increased or decreased Rubisco content using the capillary electrophoresis-time-of-flight mass spectrometry (CE-TOFMS) technique. In RBCS-sense plants, an increase in Rubisco content did not improve light-saturated photosynthesis. Glyceraldehyde 3-phosphate and sedoheputulose 7-phosphate levels increased, but ribulose bisphosphate (RuBP), ATP and ADP levels were not affected. It is considered from these results that RuBP regeneration independent of ATP supply became a bottleneck for photosynthesis. In RBCS-antisense plants, a decline in Rubisco content decreased photosynthesis with a substantial accumulation of RuBP. ATP and ADP levels also increased and were associated with increases in the diphosphate and triphosphate compounds of other nucleosides. These results imply that a decline in Rubisco content slowed down the Calvin cycle and that the resultant excess energy of ATP was transferred to other nucleoside diphosphates and triphosphates. The levels of amino acids tended to decline in RBCS-sense plants and increase in RBCS-antisense plants, probably reflecting the demand for Rubisco synthesis. Starch and carbohydrate levels decreased only in RBCS-antisense plants. Thus, genetic manipulation of Rubisco contents widely affected C and N metabolism in rice.
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Affiliation(s)
- Yuji Suzuki
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Sendai 981-8555, Japan.
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15
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Tiessen A, Nerlich A, Faix B, Hümmer C, Fox S, Trafford K, Weber H, Weschke W, Geigenberger P. Subcellular analysis of starch metabolism in developing barley seeds using a non-aqueous fractionation method. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:2071-87. [PMID: 22200665 PMCID: PMC3295393 DOI: 10.1093/jxb/err408] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 11/17/2011] [Accepted: 11/21/2011] [Indexed: 05/20/2023]
Abstract
Compartmentation of metabolism in developing seeds is poorly understood due to the lack of data on metabolite distributions at the subcellular level. In this report, a non-aqueous fractionation method is described that allows subcellular concentrations of metabolites in developing barley endosperm to be calculated. (i) Analysis of subcellular volumes in developing endosperm using micrographs shows that plastids and cytosol occupy 50.5% and 49.9% of the total cell volume, respectively, while vacuoles and mitochondria can be neglected. (ii) By using non-aqueous fractionation, subcellular distribution between the cytosol and plastid of the levels of metabolites involved in sucrose degradation, starch synthesis, and respiration were determined. With the exception of ADP and AMP which were mainly located in the plastid, most other metabolites of carbon and energy metabolism were mainly located outside the plastid in the cytosolic compartment. (iii) In developing barley endosperm, the ultimate precursor of starch, ADPglucose (ADPGlc), was mainly located in the cytosol (80-90%), which was opposite to the situation in growing potato tubers where ADPGlc was almost exclusively located in the plastid (98%). This reflects the different subcellular distribution of ADPGlc pyrophosphorylase (AGPase) in these tissues. (iv) Cytosolic concentrations of ADPGlc were found to be close to the published K(m) values of AGPase and the ADPGlc/ADP transporter at the plastid envelope. Also the concentrations of the reaction partners glucose-1-phosphate, ATP, and inorganic pyrophosphate were close to the respective K(m) values of AGPase. (v) Knock-out of cytosolic AGPase in Riso16 mutants led to a strong decrease in ADPGlc level, in both the cytosol and plastid, whereas knock-down of the ADPGlc/ADP transporter led to a large shift in the intracellular distribution of ADPGlc. (v) The thermodynamic structure of the pathway of sucrose to starch was determined by calculating the mass-action ratios of all the steps in the pathway. The data show that AGPase is close to equilibrium, in both the cytosol and plastid, whereas the ADPGlc/ADP transporter is strongly displaced from equilibrium in vivo. This is in contrast to most other tissues, including leaves and potato tubers. (vi) Results indicate transport rather than synthesis of ADPGlc to be the major regulatory site of starch synthesis in barley endosperm. The reversibility of AGPase in the plastid has important implications for the regulation of carbon partitioning between different biosynthetic pathways.
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Affiliation(s)
- Axel Tiessen
- Departamento de Ingeniería Genética, CINVESTAV, Campus Guanajuato, 36821 Irapuato, México
- Ludwig-Maximilians-Universität München, Department Biologie I, Grosshaderner Str. 2–4, D-82152 Martinsried, Germany
| | - Annika Nerlich
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, D-14476 Golm, Germany
| | - Benjamin Faix
- Ludwig-Maximilians-Universität München, Department Biologie I, Grosshaderner Str. 2–4, D-82152 Martinsried, Germany
| | - Christine Hümmer
- Ludwig-Maximilians-Universität München, Department Biologie I, Grosshaderner Str. 2–4, D-82152 Martinsried, Germany
| | - Simon Fox
- John Innes Centre, Norwich Research Park, Colney, Norwich, UK
| | - Kay Trafford
- John Innes Centre, Norwich Research Park, Colney, Norwich, UK
| | - Hans Weber
- Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), D-06466 Gatersleben, Germany
| | - Winfriede Weschke
- Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), D-06466 Gatersleben, Germany
| | - Peter Geigenberger
- Ludwig-Maximilians-Universität München, Department Biologie I, Grosshaderner Str. 2–4, D-82152 Martinsried, Germany
- To whom correspondence should be addressed. E-mail:
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16
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Okumoto S, Pilot G. Amino acid export in plants: a missing link in nitrogen cycling. MOLECULAR PLANT 2011; 4:453-63. [PMID: 21324969 PMCID: PMC3143828 DOI: 10.1093/mp/ssr003] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Accepted: 12/24/2010] [Indexed: 05/17/2023]
Abstract
The export of nutrients from source organs to parts of the body where they are required (e.g. sink organs) is a fundamental biological process. Export of amino acids, one of the most abundant nitrogen species in plant long-distance transport tissues (i.e. xylem and phloem), is an essential process for the proper distribution of nitrogen in the plant. Physiological studies have detected the presence of multiple amino acid export systems in plant cell membranes. Yet, surprisingly little is known about the molecular identity of amino acid exporters, partially due to the technical difficulties hampering the identification of exporter proteins. In this short review, we will summarize our current knowledge about amino acid export systems in plants. Several studies have described plant amino acid transporters capable of bi-directional, facilitative transport, reminiscent of activities identified by earlier physiological studies. Moreover, recent expansion in the number of available amino acid transporter sequences have revealed evolutionary relationships between amino acid exporters from other organisms with a number of uncharacterized plant proteins, some of which might also function as amino acid exporters. In addition, genes that may regulate export of amino acids have been discovered. Studies of these putative transporter and regulator proteins may help in understanding the elusive molecular mechanisms of amino acid export in plants.
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Affiliation(s)
- Sakiko Okumoto
- 549 Latham Hall, Virginia Tech, Blacksburg, VA 24061, USA.
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17
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Keerberg O, Ivanova H, Keerberg H, Pärnik T, Talts P, Gardeström P. Quantitative analysis of photosynthetic carbon metabolism in protoplasts and intact leaves of barley. Determination of carbon fluxes and pool sizes of metabolites in different cellular compartments. Biosystems 2011; 103:291-301. [DOI: 10.1016/j.biosystems.2010.10.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 10/21/2010] [Accepted: 10/22/2010] [Indexed: 11/29/2022]
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18
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Nunes-Nesi A, Fernie AR, Stitt M. Metabolic and signaling aspects underpinning the regulation of plant carbon nitrogen interactions. MOLECULAR PLANT 2010; 3:973-96. [PMID: 20926550 DOI: 10.1093/mp/ssq049] [Citation(s) in RCA: 410] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
In addition to light and water, CO(2) and mineral elements are required for plant growth and development. Among these factors, nitrogen is critical, since it is needed to synthesize amino acids, which are the building elements of protein, nucleotides, chlorophyll, and numerous other metabolites and cellular components. Therefore, nitrogen is required by plants in higher quantities and this investment in nitrogen supports the use of CO(2), water, and inorganic nitrogen to produce sugars, organic acids, and amino acids, the basic building blocks of biomass accumulation. This system is maintained by complex metabolic machinery, which is regulated at different levels according to environmental factors such as light, CO(2), and nutrient availability. Plants integrate these signals via a signaling network, which involves metabolites as well as nutrient-sensing proteins. Due to its importance, much research effort has been expended to understand how carbon and nitrogen metabolism are integrated and regulated according to the rates of photosynthesis, photorespiration, and respiration. Thus, in this article, we both discuss recent advances in carbon/nitrogen metabolisms as well as sensing and signaling systems in illuminated leaves of C3-plants and provide a perspective of the type of experiments that are now required in order to take our understanding to a higher level.
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Affiliation(s)
- Adriano Nunes-Nesi
- Max Planck Institute for Molecular Plant Physiology, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
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19
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Krueger S, Donath A, Lopez-Martin MC, Hoefgen R, Gotor C, Hesse H. Impact of sulfur starvation on cysteine biosynthesis in T-DNA mutants deficient for compartment-specific serine-acetyltransferase. Amino Acids 2010; 39:1029-42. [PMID: 20379751 DOI: 10.1007/s00726-010-0580-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Accepted: 03/22/2010] [Indexed: 12/22/2022]
Abstract
Sulfur plays a pivotal role in the cellular metabolism of many organisms. In plants, the uptake and assimilation of sulfate is strongly regulated at the transcriptional level. Regulatory factors are the demand of reduced sulfur in organic or non-organic form and the level of O-acetylserine (OAS), the carbon precursor for cysteine biosynthesis. In plants, cysteine is synthesized by action of the cysteine-synthase complex (CSC) containing serine acetyltransferase (SAT) and O-acetylserine-(thiol)-lyase (OASTL). Both enzymes are located in plastids, mitochondria and the cytosol. The function of the compartmentation of the CSC to regulate sulfate uptake and assimilation is still not clearly resolved. To address this question, we analyzed Arabidopsis thaliana mutants for the plastidic and cytosolic SAT isoenzymes under sulfur starvation conditions. In addition, subcellular metabolite analysis by non-aqueous fractionation revealed distinct changes in subcellular metabolite distribution upon short-term sulfur starvation. Metabolite and transcript analyses of SERAT1.1 and SERAT2.1 mutants [previously analyzed in Krueger et al. (Plant Cell Environ 32:349-367, 2009)] grown under sulfur starvation conditions indicate that both isoenzymes do not contribute directly to the transcriptional regulation of genes involved in sulfate uptake and assimilation. Here, we summarize the current knowledge about the regulation of cysteine biosynthesis and the contribution of the different compartments to this metabolic process. We relate hypotheses and views of the regulation of cysteine biosynthesis with our results of applying sulfur starvation to mutants impaired in compartment-specific cysteine biosynthetic enzymes.
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Affiliation(s)
- Stephan Krueger
- Max Planck Institut für Molekulare Pflanzenphysiologie, Potsdam-Golm, Germany
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20
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Schneider T, Keller F. Raffinose in chloroplasts is synthesized in the cytosol and transported across the chloroplast envelope. PLANT & CELL PHYSIOLOGY 2009; 50:2174-82. [PMID: 19880397 DOI: 10.1093/pcp/pcp151] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In chloroplasts, several water-soluble carbohydrates have been suggested to act as stress protectants. The trisaccharide raffinose (alpha-1,6-galactosyl sucrose) is such a carbohydrate but has received little attention. We here demonstrate by compartmentation analysis of leaf mesophyll protoplasts that raffinose is clearly (to about 20%) present in chloroplasts of cold-treated common bugle (Ajuga reptans L.), spinach (Spinacia oleracea L.) and Arabidopsis [Arabidopsis thaliana (L.) Heynh.] plants. The two dedicated enzymes needed for raffinose synthesis, galactinol synthase and raffinose synthase, were found to be extra-chloroplastic (probably cytosolic) in location, suggesting that the chloroplast envelope contains a raffinose transporter. Uptake experiments with isolated Ajuga and Arabidopsis chloroplasts clearly demonstrated that raffinose is indeed transported across the chloroplast envelope by a raffinose transporter, probably actively. Raffinose uptake into Ajuga chloroplasts was a saturable process with apparent K(m) and v(max) values of 27.8 mM and 3.3 micromol mg(-1) Chl min(-1), respectively.
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Affiliation(s)
- Thomas Schneider
- Molekulare Pflanzenphysiologie, Institut für Pflanzenbiologie, Universität Zürich, Zollikerstrasse 107, 8008 Zürich, Switzerland
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21
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Krueger S, Niehl A, Lopez Martin MC, Steinhauser D, Donath A, Hildebrandt T, Romero LC, Hoefgen R, Gotor C, Hesse H. Analysis of cytosolic and plastidic serine acetyltransferase mutants and subcellular metabolite distributions suggests interplay of the cellular compartments for cysteine biosynthesis in Arabidopsis. PLANT, CELL & ENVIRONMENT 2009; 32:349-367. [PMID: 19143986 DOI: 10.1111/j.1365-3040.2009.01928.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In plants, the enzymes for cysteine synthesis serine acetyltransferase (SAT) and O-acetylserine-(thiol)-lyase (OASTL) are present in the cytosol, plastids and mitochondria. However, it is still not clearly resolved to what extent the different compartments are involved in cysteine biosynthesis and how compartmentation influences the regulation of this biosynthetic pathway. To address these questions, we analysed Arabidopsis thaliana T-DNA insertion mutants for cytosolic and plastidic SAT isoforms. In addition, the subcellular distribution of enzyme activities and metabolite concentrations implicated in cysteine and glutathione biosynthesis were revealed by non-aqueous fractionation (NAF). We demonstrate that cytosolic SERAT1.1 and plastidic SERAT2.1 do not contribute to cysteine biosynthesis to a major extent, but may function to overcome transport limitations of O-acetylserine (OAS) from mitochondria. Substantiated by predominantly cytosolic cysteine pools, considerable amounts of sulphide and presence of OAS in the cytosol, our results suggest that the cytosol is the principal site for cysteine biosynthesis. Subcellular metabolite analysis further indicated efficient transport of cysteine, gamma-glutamylcysteine and glutathione between the compartments. With respect to regulation of cysteine biosynthesis, estimation of subcellular OAS and sulphide concentrations established that OAS is limiting for cysteine biosynthesis and that SAT is mainly present bound in the cysteine-synthase complex.
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Affiliation(s)
- Stephan Krueger
- Max Planck Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, France
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22
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Farre EM, Fernie AR, Willmitzer L. Analysis of subcellular metabolite levels of potato tubers (Solanum tuberosum) displaying alterations in cellular or extracellular sucrose metabolism. Metabolomics 2008; 4:161-170. [PMID: 19816536 PMCID: PMC2758360 DOI: 10.1007/s11306-008-0107-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2007] [Accepted: 02/01/2008] [Indexed: 11/29/2022]
Abstract
The expression of a heterologous invertase in potato tubers (Solanum tuberosum) in either the cytosol or apoplast leads to a decrease in total sucrose content and to an increase in glucose. Depending on the targeting of the enzyme different changes in phenotype and metabolism of the tubers occur: the cytosolic invertase expressing tubers show an increase in the glycolytic flux, accumulation of amino acids and organic acids, and the appearance of novel disaccharides; however, these changes are not observed when the enzyme is expressed in the apoplast [Roessner et al. (2001). Plant Cell, 13, 11-29]. The analysis of these lines raised several questions concerning the regulation of compartmentation of metabolites in potato tubers. In the current study we addressed these questions by performing comparative subcellular metabolite profiling. We demonstrate that: (i) hexoses accumulate in the vacuole independently of their site of production, but that the cytosolic invertase expression led to a strong increase in the cytosolic glucose concentration and decrease in cytosolic sucrose, whereas these effects were more moderate in the apoplastic expressors; (ii) three out of four of the novel compounds found in the cytosolic overexpressors accumulate in the same compartment; (iii) despite changes in absolute cellular content the subcellular distribution of amino acids was invariant in the invertase overexpressing tubers. These results are discussed in the context of current models of the compartmentation of primary metabolism in heterotrophic plant tissues. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11306-008-0107-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Eva M. Farre
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
- Department of Developmental and Cell Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093 USA
| | - Alisdair R. Fernie
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
| | - Lothar Willmitzer
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
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23
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Nadwodnik J, Lohaus G. Subcellular concentrations of sugar alcohols and sugars in relation to phloem translocation in Plantago major, Plantago maritima, Prunus persica, and Apium graveolens. PLANTA 2008; 227:1079-89. [PMID: 18188589 PMCID: PMC2270920 DOI: 10.1007/s00425-007-0682-0] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2007] [Accepted: 12/07/2007] [Indexed: 05/18/2023]
Abstract
Sugar and sugar alcohol concentrations were analyzed in subcellular compartments of mesophyll cells, in the apoplast, and in the phloem sap of leaves of Plantago major (common plantain), Plantago maritima (sea plantain), Prunus persica (peach) and Apium graveolens (celery). In addition to sucrose, common plantain, sea plantain, and peach also translocated substantial amounts of sorbitol, whereas celery translocated mannitol as well. Sucrose was always present in vacuole and cytosol of mesophyll cells, whereas sorbitol and mannitol were found in vacuole, stroma, and cytosol in all cases except for sea plantain. The concentration of sorbitol, mannitol and sucrose in phloem sap was 2- to 40-fold higher than that in the cytosol of mesophyll cells. Apoplastic carbohydrate concentrations in all species tested were in the low millimolar range versus high millimolar concentrations in symplastic compartments. Therefore, the concentration ratios between the apoplast and the phloem were very strong, ranging between 20- to 100-fold for sorbitol and mannitol, and between 200- and 2000-fold for sucrose. The woody species, peach, showed the smallest concentration ratios between the cytosol of mesophyll cells and the phloem as well as between the apoplast and the phloem, suggesting a mixture of apoplastic and symplastic phloem loading, in contrast to the herbal plant species (common plantain, sea plantain, celery) which likely exhibit an active loading mode for sorbitol and mannitol as well as sucrose from the apoplast into the phloem.
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Affiliation(s)
- Jan Nadwodnik
- Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Biochemie der Pflanze, Universität Göttingen, Untere Karspüle 2, 37073 Gottingen, Germany
| | - Gertrud Lohaus
- Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Biochemie der Pflanze, Universität Göttingen, Untere Karspüle 2, 37073 Gottingen, Germany
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24
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Liu YJ, Norberg FEB, Szilágyi A, De Paepe R, Akerlund HE, Rasmusson AG. The mitochondrial external NADPH dehydrogenase modulates the leaf NADPH/NADP+ ratio in transgenic Nicotiana sylvestris. PLANT & CELL PHYSIOLOGY 2008; 49:251-63. [PMID: 18182402 DOI: 10.1093/pcp/pcn001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Plant mitochondria contain alternative external NAD(P)H dehydrogenases, which oxidize cytosolic NADH or NADPH and reduce ubiquinone without inherent linkage to proton pumping and ATP production. In potato, St-NDB1 is an external Ca2+-dependent NADPH dehydrogenase. The physiological function of this enzyme was investigated in homozygous Nicotiana sylvestris lines overexpressing St-ndb1 and co-suppressing St-ndb1 and an N. sylvestris ndb1. In leaf mitochondria isolated from the overexpressor lines, higher activity of alternative oxidase (AOX) was detected. However, the AOX induction was substantially weaker than in the complex I-deficient CMSII mutant, previously shown to contain elevated amounts of NAD(P)H dehydrogenases and AOX. An aox1b and an aox2 gene were up-regulated in CMSII, but only aox1b showed a response, albeit smaller, in the transgenic lines, indicating differences in AOX activation between the genotypes. As in CMSII, the increase of AOX in the overexpressing lines was not due to a general oxidative stress. The lines overexpressing St-ndb1 had consistently lowered leaf NADPH/NADP+ ratios in the light and variably decreased levels in darkness, but unchanged NADH/NAD+ ratios. CMSII instead had similar NADPH/NADP+ and lower NADH/NAD+ ratios than the wild type. These results demonstrate that St-NDB1 is able to modulate the cellular balance of NADPH and NADP+ at least in the day and that reduction of NADP(H) and NAD(H) is independently controlled. Similar growth rates, chloroplast malate dehydrogenase activation and xanthophyll ratios indicate that the change in reduction does not communicate to the chloroplast, and that the cell tolerates significant changes in NADP(H) reduction without deleterious effects.
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Affiliation(s)
- Yun-Jun Liu
- Lund University, Department of Cell and Organism Biology, Sölvegatan 35B, SE-22362 Lund, Sweden
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25
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Zhu XG, de Sturler E, Long SP. Optimizing the distribution of resources between enzymes of carbon metabolism can dramatically increase photosynthetic rate: a numerical simulation using an evolutionary algorithm. PLANT PHYSIOLOGY 2007; 145:513-26. [PMID: 17720759 PMCID: PMC2048738 DOI: 10.1104/pp.107.103713] [Citation(s) in RCA: 238] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Accepted: 07/22/2007] [Indexed: 05/16/2023]
Abstract
The distribution of resources between enzymes of photosynthetic carbon metabolism might be assumed to have been optimized by natural selection. However, natural selection for survival and fecundity does not necessarily select for maximal photosynthetic productivity. Further, the concentration of a key substrate, atmospheric CO(2), has changed more over the past 100 years than the past 25 million years, with the likelihood that natural selection has had inadequate time to reoptimize resource partitioning for this change. Could photosynthetic rate be increased by altered partitioning of resources among the enzymes of carbon metabolism? This question is addressed using an "evolutionary" algorithm to progressively search for multiple alterations in partitioning that increase photosynthetic rate. To do this, we extended existing metabolic models of C(3) photosynthesis by including the photorespiratory pathway (PCOP) and metabolism to starch and sucrose to develop a complete dynamic model of photosynthetic carbon metabolism. The model consists of linked differential equations, each representing the change of concentration of one metabolite. Initial concentrations of metabolites and maximal activities of enzymes were extracted from the literature. The dynamics of CO(2) fixation and metabolite concentrations were realistically simulated by numerical integration, such that the model could mimic well-established physiological phenomena. For example, a realistic steady-state rate of CO(2) uptake was attained and then reattained after perturbing O(2) concentration. Using an evolutionary algorithm, partitioning of a fixed total amount of protein-nitrogen between enzymes was allowed to vary. The individual with the higher light-saturated photosynthetic rate was selected and used to seed the next generation. After 1,500 generations, photosynthesis was increased substantially. This suggests that the "typical" partitioning in C(3) leaves might be suboptimal for maximizing the light-saturated rate of photosynthesis. An overinvestment in PCOP enzymes and underinvestment in Rubisco, sedoheptulose-1,7-bisphosphatase, and fructose-1,6-bisphosphate aldolase were indicated. Increase in sink capacity, such as increase in ADP-glucose pyrophosphorylase, was also indicated to lead to increased CO(2) uptake rate. These results suggest that manipulation of partitioning could greatly increase carbon gain without any increase in the total protein-nitrogen investment in the apparatus for photosynthetic carbon metabolism.
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Affiliation(s)
- Xin-Guang Zhu
- Department of Plant Biology and Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Kruger NJ, Le Lay P, Ratcliffe RG. Vacuolar compartmentation complicates the steady-state analysis of glucose metabolism and forces reappraisal of sucrose cycling in plants. PHYTOCHEMISTRY 2007; 68:2189-96. [PMID: 17524437 DOI: 10.1016/j.phytochem.2007.04.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2007] [Revised: 03/30/2007] [Accepted: 04/03/2007] [Indexed: 05/02/2023]
Abstract
Steady-state stable isotope labelling provides a method for generating flux maps of the compartmented network of central metabolism in heterotrophic plant tissues. Theoretical analysis of the contribution of the vacuole to the regeneration of glucose by endogenous processes shows that numerical fitting of isotopomeric data will only generate an accurate map of the fluxes involving intracellular glucose if information is available on the labelling of both the cytosolic and vacuolar glucose pools. In the absence of this information many of the calculated fluxes are at best unreliable or at worst indeterminate. This result suggests that the anomalously high rates of sucrose cycling and glucose resynthesis that have been reported in earlier steady-state analyses of tissues labelled with (13)C-glucose precursors may be an artefact of assuming that the labelling pattern of extracted glucose reflected the labelling of the cytosolic pool. The analysis emphasises that although subcellular information can sometimes be deduced from a steady-state analysis without recourse to subcellular fractionation, the success of this procedure depends critically on the structure of the metabolic network. It is concluded that methods need to be implemented that will allow measurement of the subcellular labelling pattern of glucose and other metabolites, as part of the routine analysis of the redistribution of label in steady-state stable isotope labelling experiments, if the true potential of network flux analysis for generating metabolic phenotypes is to be realized.
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Affiliation(s)
- Nicholas J Kruger
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
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Gagneul D, Aïnouche A, Duhazé C, Lugan R, Larher FR, Bouchereau A. A reassessment of the function of the so-called compatible solutes in the halophytic plumbaginaceae Limonium latifolium. PLANT PHYSIOLOGY 2007; 144:1598-611. [PMID: 17468212 PMCID: PMC1914112 DOI: 10.1104/pp.107.099820] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The compatible solute hypothesis posits that maintaining osmotic equilibrium under conditions of high salinity requires synthesis of organic compounds, uptake of potassium ions, and partial exclusion of NaCl. To assess whether osmotic adaptation in Limonium latifolium proceeds according to this hypothesis, a comprehensive analysis of solute accumulation during NaCl treatments was conducted. Determination of prevailing inorganic ions and establishment of the metabolic profiles for low M(r) organic substances revealed that contrary to the mentioned hypothesis the major contributors to osmolarity were constituted by inorganic solutes. Independent of salinity, only 25% of this osmolarity resulted from organic solutes such as Suc and hexoses. Proline (Pro), beta-alanine betaine, and choline-O-sulfate were minor contributors to osmolarity. Compatible inositols also occurred, especially chiro-inositol, characterized for the first time in this species, to our knowledge. Principal component analysis showed that only a limited number of metabolic reconfigurations occurred in response to dynamic changes in salinity. Under such conditions only sugars, chiro-inositol, and Pro behave as active osmobalancers. Analysis of metabolic profiles during acclimatization to either mild salinity or nonsaline conditions showed that organic solute accumulation is predominantly controlled by constitutive developmental programs, some of which might be slightly modulated by salinity. Osmolarity provided under such conditions can be sufficient to maintain turgor in salinized seedlings. Compartmental analysis of Pro and beta-alanine betaine in leaf tissues demonstrated that these solutes, mainly located in vacuoles under nonsaline conditions, could be partly directed to the cytosol in response to salinization. Thus they did not conform with the predictions of the compatible solute hypothesis.
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Affiliation(s)
- David Gagneul
- Unité Mixte de Recherche 6026 Interactions Cellulaires et Moléculaires and Unité Mixte de Recherche 6553 Ecosystèmes, Biodiversité, Evolution , Université de Rennes 1, Centre National de la Recherche Scientifique, Campus de Beaulieu, Rennes Cedex, France
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Fritz C, Mueller C, Matt P, Feil R, Stitt M. Impact of the C-N status on the amino acid profile in tobacco source leaves. PLANT, CELL & ENVIRONMENT 2006; 29:2055-76. [PMID: 17081241 DOI: 10.1111/j.1365-3040.2006.01580.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
This paper investigates the influence of the carbon (C) and nitrogen (N) status on the amino acid profile in tobacco source leaves. Treatments used included growing plants at different light intensities, using an antisense RBCS (small subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase) construct to inhibit Rubisco activity, growing plants on 12 or 0.5 mM nitrate, comparing wild-types with genotypes that have small and large decreases in nitrate reductase (NIA) activity, and sampling plants at different times during the diurnal cycle. This combination of experiments provides information on how amino acid levels respond to several inputs including the C and N status, nitrate, excess light and light-dark transitions. The data set was analysed using principal component analysis, regression analysis and by normalizing the level of each individual amino acid on the total amino acid pool. Most amino acids show a downward trend when the C or the N status is decreased, and rise during day and fall at night during the diurnal cycle. However, individual amino acids often showed deviating responses. Furthermore, no evidence was found for feedback inhibition of minor amino acid synthesis, either within or between pathways, when 18 individual amino acids were supplied to detached leaves. Results indicate that regulation of amino acid metabolism, for example by the C and N status, leads to qualitatively similar responses of many amino acids, but homeostatic mechanisms involving feedback inhibition within or between individual amino acid biosynthesis pathways are not stringent. All of the above inputs affect the level of phenylalanine, an amino acid that is also the substrate for an important sector of secondary metabolism. The levels of glutamate were remarkably constant, indicating that unknown mechanisms stabilize the concentration of this key central amino acid. Analyses of metabolite levels and feeding experiments indicated that 2-oxoglutarate plays an important role in regulating glutamate levels. Glutamate was the most effective inhibitor of NIA activity when 18 individual amino acids were supplied to detached leaves. Feeding glutamate, and other downstream amino acids, led to an increase of glutamine, indicating glutamate exerts feedback regulation on ammonium metabolism.
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Affiliation(s)
- Christina Fritz
- Max Planck Institute for Molecular Plant Physiology, Am Muehlenberg 1, 14474 Golm, Germany
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Voitsekhovskaja OV, Koroleva OA, Batashev DR, Knop C, Tomos AD, Gamalei YV, Heldt HW, Lohaus G. Phloem loading in two Scrophulariaceae species. What can drive symplastic flow via plasmodesmata? PLANT PHYSIOLOGY 2006; 140:383-95. [PMID: 16377750 PMCID: PMC1326059 DOI: 10.1104/pp.105.068312] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2005] [Revised: 10/31/2005] [Accepted: 11/03/2005] [Indexed: 05/05/2023]
Abstract
To determine the driving forces for symplastic sugar flux between mesophyll and phloem, gradients of sugar concentrations and osmotic pressure were studied in leaf tissues of two Scrophulariaceae species, Alonsoa meridionalis and Asarina barclaiana. A. meridionalis has a typical symplastic configuration of minor-vein phloem, i.e. intermediary companion cells with highly developed plasmodesmal connections to bundle-sheath cells. In A. barclaiana, two types of companion cells, modified intermediary cells and transfer cells, were found in minor-vein phloem, giving this species the potential to have a complex phloem-loading mode. We identified all phloem-transported carbohydrates in both species and analyzed the levels of carbohydrates in chloroplasts, vacuoles, and cytoplasm of mesophyll cells by nonaqueous fractionation. Osmotic pressure was measured in single epidermal and mesophyll cells and in whole leaves and compared with calculated values for phloem sap. In A. meridionalis, a 2-fold concentration gradient for sucrose between mesophyll and phloem was found. In A. barclaiana, the major transported carbohydrates, sucrose and antirrhinoside, were present in the phloem in 22- and 6-fold higher concentrations, respectively, than in the cytoplasm of mesophyll cells. The data show that diffusion of sugars along their concentration gradients is unlikely to be the major mechanism for symplastic phloem loading if this were to occur in these species. We conclude that in both A. meridionalis and A. barclaiana, apoplastic phloem loading is an indispensable mechanism and that symplastic entrance of solutes into the phloem may occur by mass flow. The conditions favoring symplastic mass flow into the phloem are discussed.
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Affiliation(s)
- Olga V Voitsekhovskaja
- Albrecht-von-Haller-Institute for Plant Sciences, Plant Biochemistry, 37077 Goettingen, Germany.
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Hudson AO, Singh BK, Leustek T, Gilvarg C. An LL-diaminopimelate aminotransferase defines a novel variant of the lysine biosynthesis pathway in plants. PLANT PHYSIOLOGY 2006; 140:292-301. [PMID: 16361515 PMCID: PMC1326051 DOI: 10.1104/pp.105.072629] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Although lysine (Lys) biosynthesis in plants is known to occur by way of a pathway that utilizes diaminopimelic acid (DAP) as a central intermediate, the available evidence suggests that none of the known DAP-pathway variants found in nature occur in plants. A new Lys biosynthesis pathway has been identified in Arabidopsis (Arabidopsis thaliana) that utilizes a novel transaminase that specifically catalyzes the interconversion of tetrahydrodipicolinate and LL-diaminopimelate, a reaction requiring three enzymes in the DAP-pathway variant found in Escherichia coli. The LL-DAP aminotransferase encoded by locus At4g33680 was able to complement the dapD and dapE mutants of E. coli. This result, in conjunction with the kinetic properties and substrate specificity of the enzyme, indicated that LL-DAP aminotransferase functions in the Lys biosynthetic direction under in vivo conditions. Orthologs of At4g33680 were identified in all the cyanobacterial species whose genomes have been sequenced. The Synechocystis sp. ortholog encoded by locus sll0480 showed the same functional properties as At4g33680. These results demonstrate that the Lys biosynthesis pathway in plants and cyanobacteria is distinct from the pathways that have so far been defined in microorganisms.
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Affiliation(s)
- André O Hudson
- Biotech Center and Department of Plant Biology and Pathology, Rutgers University, New Brunswick, New Jersey 08901, USA
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Abstract
Isoprenoids represent the oldest class of known low molecular-mass natural products synthesized by plants. Their biogenesis in plastids, mitochondria and the endoplasmic reticulum-cytosol proceed invariably from the C5 building blocks, isopentenyl diphosphate and/or dimethylallyl diphosphate according to complex and reiterated mechanisms. Compounds derived from the pathway exhibit a diverse spectrum of biological functions. This review centers on advances obtained in the field based on combined use of biochemical, molecular biology and genetic approaches. The function and evolutionary implications of this metabolism are discussed in relation with seminal informations gathered from distantly but related organisms.
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Affiliation(s)
- Florence Bouvier
- Institut de Biologie Moléculaire des Plantes du CNRS (UPR2357) et Université Louis Pasteur, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France
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Deuschle K, Fehr M, Hilpert M, Lager I, Lalonde S, Looger LL, Okumoto S, Persson J, Schmidt A, Frommer WB. Genetically encoded sensors for metabolites. Cytometry A 2005; 64:3-9. [PMID: 15688353 PMCID: PMC2752217 DOI: 10.1002/cyto.a.20119] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Metabolomics, i.e., the multiparallel analysis of metabolite changes occurring in a cell or an organism, has become feasible with the development of highly efficient mass spectroscopic technologies. Functional genomics as a standard tool helped to identify the function of many of the genes that encode important transporters and metabolic enzymes over the past few years. Advanced expression systems and analysis technologies made it possible to study the biochemical properties of the corresponding proteins in great detail. We begin to understand the biological functions of the gene products by systematic analysis of mutants using systematic PTGS/RNAi, knockout and TILLING approaches. However, one crucial set of data especially relevant in the case of multicellular organisms is lacking: the knowledge of the spatial and temporal profiles of metabolite levels at cellular and subcellular levels. METHODS We therefore developed genetically encoded nanosensors for several metabolites to provide a basic set of tools for the determination of cytosolic and subcellular metabolite levels in real time by using fluorescence microscopy. RESULTS Prototypes of these sensors were successfully used in vitro and also in vivo, i.e., to measure sugar levels in fungal and animal cells. CONCLUSIONS One of the future goals will be to expand the set of sensors to a wider spectrum of substrates by using the natural spectrum of periplasmic binding proteins from bacteria and by computational design of proteins with altered binding pockets in conjunction with mutagenesis. This toolbox can then be applied for four-dimensional imaging of cells and tissues to elucidate the spatial and temporal distribution of metabolites as a discovery tool in functional genomics, as a tool for high-throughput, high-content screening for drugs, to test metabolic models, and to analyze the interplay of cells in a tissue or organ.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Wolf B. Frommer
- Correspondence to: Wolf B. Frommer, Ph.D., Carnegie Institution of Washington, 260 Panama Street, Stanford, CA 94305-4101., E-mail:
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Zhou R, Cheng L. Binding of 3-phosphoglycerate leads to both activation and stabilisation of ADP-glucose pyrophosphorylase from apple leaves. FUNCTIONAL PLANT BIOLOGY : FPB 2005; 32:839-848. [PMID: 32689181 DOI: 10.1071/fp05055] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2005] [Accepted: 05/04/2005] [Indexed: 06/11/2023]
Abstract
Apple leaf ADP-glucose pyrophosphorylase was purified 1436-fold to apparent homogeneity with a specific activity of 58.9 units mg-1. The enzyme was activated by 3-phosphoglycerate (PGA) and inhibited by inorganic phosphate (Pi) in the ADPG synthesis direction. In the pyrophosphorolytic direction, however, high concentrations of PGA (> 2.5 mm) inhibited the enzyme activity. The enzyme was resistant to thermal inactivation with a T0.5 (temperature at which 50% of the enzyme activity is lost after 5 min incubation) of 52°C. Incubation with 2 mm PGA or 2 mm Pi increased T0.5 to 68°C. Incubation with 2 mm dithiothreitol (DTT) decreased T0.5 to 42°C, whereas inclusion of 2 mm PGA in the DTT incubation maintained T0.5 at 52°C. DTT-induced decrease in thermal stability was accompanied by monomerisation of the small subunits. Presence of PGA in the DTT incubation did not alter the monomerisation of the small subunits of the enzyme induced by DTT. These findings indicate that binding of PGA renders apple leaf AGPase with a conformation that is not only more efficient in catalysis but also more stable to heat treatment. The physiological significance of the protective effect of PGA on thermal inactivation of AGPase is discussed.
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Affiliation(s)
- Rui Zhou
- Department of Horticulture, Cornell University, Ithaca, NY 14853, USA
| | - Lailiang Cheng
- Department of Horticulture, Cornell University, Ithaca, NY 14853, USA
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Tilsner J, Kassner N, Struck C, Lohaus G. Amino acid contents and transport in oilseed rape (Brassica napus L.) under different nitrogen conditions. PLANTA 2005; 221:328-38. [PMID: 15599760 DOI: 10.1007/s00425-004-1446-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2004] [Accepted: 11/03/2004] [Indexed: 05/03/2023]
Abstract
Oilseed rape (Brassica napus L.) needs very high nitrogen fertilizer inputs. Significant amounts of this nitrogen are lost during early leaf shedding and are a source of environmental and economic concern. The objective of this study was to investigate whether the remobilization of leaf amino acids could be limiting for nitrogen use efficiency. Therefore, amino acid concentrations were analyzed in subcellular compartments of leaf mesophyll cells of plants grown under low (0.5 mM NO3-) and high (4 mM NO3-) nitrogen supply. With high nitrogen supply, young leaves showed an elevated amino acid content, mainly in vacuoles. In old leaves, however, subcellular concentrations were similar under high and low nitrogen conditions, showing that the excess nitrogen had been exported during leaf development. The phloem sap contained up to 650 mM amino acids, more than four times as much than the cytosol of mesophyll cells, indicating a very efficient phloem-loading process. Three amino acid permeases, BnAAP1, BnAAP2, and BnAAP6, were identified and characterized. BnAAP1 and BnAAP6 mediated uptake of neutral and acidic amino acids into Xenopus laevis oocytes at the actual apoplastic substrate concentrations. All three transporters were expressed in leaves and the expression was still detectable during leaf senescence, with BnAAP1 and BnAAP2 mRNA levels increasing from mature to old leaves. We conclude that phloem loading of amino acids is not limiting for nitrogen remobilization from senescing leaves in oilseed rape.
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Affiliation(s)
- Jens Tilsner
- Biochemie der Pflanze, Göttinger Zentrum für Molekulare Biowissenschaften, Universität Göttingen, Justus-von-Liebig-Weg 11, 37077, Göttingen, Germany
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Fehr M, Okumoto S, Deuschle K, Lager I, Looger LL, Persson J, Kozhukh L, Lalonde S, Frommer WB. Development and use of fluorescent nanosensors for metabolite imaging in living cells. Biochem Soc Trans 2005; 33:287-90. [PMID: 15667328 DOI: 10.1042/bst0330287] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
To understand metabolic networks, fluxes and regulation, it is crucial to be able to determine the cellular and subcellular levels of metabolites. Methods such as PET and NMR imaging have provided us with the possibility of studying metabolic processes in living organisms. However, at present these technologies do not permit measuring at the subcellular level. The cameleon, a fluorescence resonance energy transfer (FRET)-based nanosensor uses the ability of the calcium-bound form of calmodulin to interact with calmodulin binding polypeptides to turn the corresponding dramatic conformational change into a change in resonance energy transfer between two fluorescent proteins attached to the fusion protein. The cameleon and its derivatives were successfully used to follow calcium changes in real time not only in isolated cells, but also in living organisms. To provide a set of tools for real-time measurements of metabolite levels with subcellular resolution, protein-based nanosensors for various metabolites were developed. The metabolite nanosensors consist of two variants of the green fluorescent protein fused to bacterial periplasmic binding proteins. Different from the cameleon, a conformational change in the binding protein is directly detected as a change in FRET efficiency. The prototypes are able to detect various carbohydrates such as ribose, glucose and maltose as purified proteins in vitro. The nanosensors can be expressed in yeast and in mammalian cell cultures and were used to determine carbohydrate homeostasis in living cells with subcellular resolution. One future goal is to expand the set of sensors to cover a wider spectrum of metabolites by using the natural spectrum of bacterial periplasmic binding proteins and by computational design of the binding pockets of the prototype sensors.
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Affiliation(s)
- M Fehr
- Carnegie Institution, Plant Biology, 260 Panama St., Stanford, CA 94305, USA
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Fehr M, Ehrhardt DW, Lalonde S, Frommer WB. Minimally invasive dynamic imaging of ions and metabolites in living cells. CURRENT OPINION IN PLANT BIOLOGY 2004; 7:345-51. [PMID: 15134757 DOI: 10.1016/j.pbi.2004.03.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
By 2010, it is expected that biochemical functions will be assigned to many of the products of the approximately 30,000 Arabidopsis genes. Moreover, systematic analysis of mutants will provide insight into the biological function of the gene products. Metabolomic technologies complement these approaches by testing for changes in cellular ion and metabolite patterns, providing essential information for the construction of cellular and whole-plant models of metabolism. However, one important set of information that is especially relevant for multicellular organisms is still lacking, that is, knowledge of the cellular and subcellular variation in metabolite levels. The recent development of protein-based nanosensors for metabolites will help to close this gap by providing a set of tools that can be used to determine cytosolic and subcellular metabolite levels in real time using fluorescence-based microscopy. A major challenge for the future is the application of these nanosensors to quantify metabolite levels in plant cells and tissues.
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Affiliation(s)
- Marcus Fehr
- Carnegie Institution of Washington, Plant Biology, 260 Panama Street, Stanford, California 94305, USA
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Lalonde S, Wipf D, Frommer WB. Transport mechanisms for organic forms of carbon and nitrogen between source and sink. ANNUAL REVIEW OF PLANT BIOLOGY 2004; 55:341-72. [PMID: 15377224 DOI: 10.1146/annurev.arplant.55.031903.141758] [Citation(s) in RCA: 240] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Sugars and amino acids are generated in plants by assimilation from inorganic forms. Assimilated forms cross multiple membranes on their way from production sites to storage or use locations. Specific transport systems are responsible for vacuolar uptake and release, for efflux from the cells, and for uptake into the vasculature. Detailed phylogenetic analyses suggest that only proton-coupled cotransporters involved in phloem loading have been identified to date, whereas systems for vacuolar transport and efflux still await identification. Novel imaging approaches may provide the means to characterize the cellular events and elucidate whole plant control of assimilate partitioning and allocation.
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Knop C, Stadler R, Sauer N, Lohaus G. AmSUT1, a sucrose transporter in collection and transport phloem of the putative symplastic phloem loader Alonsoa meridionalis. PLANT PHYSIOLOGY 2004; 134:204-14. [PMID: 14730068 PMCID: PMC316300 DOI: 10.1104/pp.103.029264] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Revised: 09/10/2003] [Accepted: 10/05/2003] [Indexed: 05/19/2023]
Abstract
A sucrose (Suc) transporter cDNA has been cloned from Alonsoa meridionalis, a member of the Scrophulariaceae. This plant species has an open minor vein configuration and translocates mainly raffinose and stachyose in addition to Suc in the phloem (C. Knop, O. Voitsekhovskaja, G. Lohaus [2001] Planta 213: 80-91). These are typical properties of symplastic phloem loaders. For functional characterization, AmSUT1 cDNA was expressed in bakers' yeast (Saccharomyces cerevisiae). Substrate and inhibitor specificities, energy dependence, and Km value of the protein agree well with the properties measured for other Suc transporters of apoplastic phloem loaders. A polyclonal antiserum against the 17 N-terminal amino acids of the A. meridionalis Suc transporter AmSUT1 was used to determine the cellular localization of the AmSUT1 protein. Using fluorescence labeling on sections from A. meridionalis leaves and stems, AmSUT1 was localized exclusively in phloem cells. Further histological characterization identified these cells as companion cells and sieve elements. p-Chloromercuribenzenesulfonic acid affected the sugar exudation of cut leaves in such a way that the exudation rates of Suc and hexoses decreased, whereas those of raffinose and stachyose increased. The data presented indicate that phloem loading of Suc and retrieval of Suc in A. meridionalis are at least partly mediated by the activity of AmSUT1 in addition to symplastic phloem loading.
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Affiliation(s)
- Christian Knop
- Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Abteilung Biochemie der Pflanze, Universität Göttingen, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
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Igamberdiev AU, Gardeström P. Regulation of NAD- and NADP-dependent isocitrate dehydrogenases by reduction levels of pyridine nucleotides in mitochondria and cytosol of pea leaves. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1606:117-25. [PMID: 14507432 DOI: 10.1016/s0005-2728(03)00106-3] [Citation(s) in RCA: 171] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Regulation of NAD- and NADP-dependent isocitrate dehydrogenases (NAD-ICDH, EC 1.1.1.41, and NADP-ICDH, EC 1.1.1.42) by the level of reduced and oxidized pyridine nucleotides has been investigated in pea (Pisum sativum L.) leaves. The affinities of mitochondrial and cytosolic ICDH enzymes to substrates and inhibitors were determined on partially purified preparations in forward and reverse directions. From the kinetic data, it follows that NADP(+)- and NAD(+)-dependent isocitrate dehydrogenases in mitochondria represent a system strongly responding to the intramitochondrial NADPH and NADH levels. The NADPH, NADP(+), NADH and NAD(+) concentrations were determined by subcellular fractionation of pea leaf protoplasts using membrane filtration in mitochondria and cytosol in darkness and in the light under saturating and limiting CO(2) conditions. The cytosolic NADPH/NADP ratio was about 1 and almost constant both in darkness and in the light. In mitochondria, the NADPH/NADP ratio was low in darkness (0.2) and increased in the light, reaching 3 in limiting CO(2) conditions compared to 1 in saturating CO(2). At high reduction levels of NADP and NAD observed at limiting CO(2) in the light, i.e. when photorespiratory glycine is the main mitochondrial substrate, isocitrate oxidation in mitochondria will be suppressed and citrate will be transported to the cytosol ('citrate valve'), where the cytosolic NADP-ICDH supplies 2-oxoglutarate for the photorespiratory ammonia refixation.
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Affiliation(s)
- Abir U Igamberdiev
- Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, 901 87 Umeå, Sweden.
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Rademacher T, Häusler RE, Hirsch HJ, Zhang L, Lipka V, Weier D, Kreuzaler F, Peterhänsel C. An engineered phosphoenolpyruvate carboxylase redirects carbon and nitrogen flow in transgenic potato plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 32:25-39. [PMID: 12366798 DOI: 10.1046/j.1365-313x.2002.01397.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Phosphoenolpyruvate carboxylase (PEPC) plays a central role in the anaplerotic provision of carbon skeletons for amino acid biosynthesis in leaves of C3 plants. Furthermore, in both C4 and CAM plants photosynthetic isoforms are pivotal for the fixation of atmospheric CO2. Potato PEPC was mutated either by modifications of the N-terminal phosphorylation site or by an exchange of an internal cDNA segment for the homologous sequence of PEPC from the C4 plant Flaveria trinervia. Both modifications resulted in enzymes with lowered sensitivity to malate inhibition and an increased affinity for PEP. These effects were enhanced by a combination of both mutated sequences and pulse labelling with 14CO2 in vivo revealed clearly increased fixation into malate for this genotype. Activity levels correlated well with protein levels of the mutated PEPC. Constitutive overexpression of PEPC carrying both N-terminal and internal modifications strongly diminished plant growth and tuber yield. Metabolite analysis showed that carbon flow was re-directed from soluble sugars and starch to organic acids (malate) and amino acids, which increased four-fold compared with the wild type. The effects on leaf metabolism indicate that the engineered enzyme provides an optimised starting point for the installation of a C4-like photosynthetic pathway in C3 plants.
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Affiliation(s)
- Thomas Rademacher
- Aachen University, Institute for Biology I, Worringer Weg 1, 52056 Aachen, Germany
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41
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Rosenstiel TN, Fisher AJ, Fall R, Monson RK. Differential accumulation of dimethylallyl diphosphate in leaves and needles of isoprene- and methylbutenol-emitting and nonemitting species. PLANT PHYSIOLOGY 2002; 129:1276-84. [PMID: 12114581 PMCID: PMC166521 DOI: 10.1104/pp.002717] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2002] [Accepted: 03/06/2002] [Indexed: 05/20/2023]
Abstract
The biosynthesis and emission of volatile plant terpenoids, such as isoprene and methylbutenol (MBO), depend on the chloroplastic production of dimethylallyl diphosphate (DMAPP). To date, it has been difficult to study the relationship of cellular DMAPP levels to emission of these volatiles because of the lack of a sensitive assay for DMAPP in plant tissues. Using a recent DMAPP assay developed in our laboratories, we report that species with the highest potential for isoprene and MBO production also exhibit elevated light-dependent DMAPP production, ranging from 110% to 1,063%. Even species that do not produce significant amounts of volatile terpenoids, however, exhibit some potential for light-dependent production of DMAPP. We used a nonaqueous fractionation technique to determine the intracellular distribution of DMAPP in isoprene-emitting cottonwood (Populus deltoides) leaves; approximately 65% to 70% of the DMAPP recovered at midday occurred in the chloroplasts, indicating that most of the light-dependent production of DMAPP was chloroplastic in origin. The midday concentration of chloroplastic DMAPP in cottonwood leaves is estimated to be 0.13 to 3.0 mM, which is consistent with the relatively high K(m)s that have been reported for isoprene synthases (0.5-8 mM). The results provide support for the hypothesis that the light dependence of isoprene and MBO emissions is in part due to controls over DMAPP production.
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Affiliation(s)
- Todd N Rosenstiel
- Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, Colorado 80309-0334, USA
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42
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Weber A, Flügge UI. Interaction of cytosolic and plastidic nitrogen metabolism in plants. JOURNAL OF EXPERIMENTAL BOTANY 2002; 53:865-874. [PMID: 11912229 DOI: 10.1093/jexbot/53.370.865] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In angiosperms, the assimilation of ammonia resulting from nitrate reduction and from photorespiration depends on the operation of the plastidic GS/GOGAT cycle. The precursor for ammonia assimilation, 2-oxoglutarate, is synthesized in the mitochondria and in the cytosol. It is imported into the plastid by a 2-oxoglutarate/malate translocator (DiT1). In turn, the product of ammonia assimilation, glutamate, is exported from the plastids by a glutamate/malate translocator (DiT2). These transport processes link plastidic and cytosolic nitrogen metabolism and are essential for plant metabolism. DiT1 was purified to homogeneity from spinach chloroplast envelope membranes and identified as a protein with an apparent molecular mass of 45 kDa. Peptide sequences were obtained from the protein and the corresponding cDNA was cloned. The function of the DiT1 protein and its substrate specificity were confirmed by expression of the cDNA in yeast cells and functional reconstitution of the recombinant protein into liposomes. Recent advances in the molecular cloning of DiT2 and in the analysis of the in vivo function of DiT1 by antisense repression in transgenic tobacco plants will be discussed. In non-green tissues, the reducing equivalents required for glutamate formation by NADH-GOGAT are supplied by the oxidative pentose phosphate pathway. Glucose 6-phosphate, the immediate precursor of the oxidative pentose phosphate pathway is generated in the cytosol and imported into the plastids by the plastidic glucose 6-phosphate/phosphate translocator.
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Affiliation(s)
- Andreas Weber
- Universität zu Köln, Lehrstuhl Botanik II, Gyrhofstr. 15, D-50931 Köln, Germany.
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43
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Noctor G, Novitskaya L, Lea PJ, Foyer CH. Co-ordination of leaf minor amino acid contents in crop species: significance and interpretation. JOURNAL OF EXPERIMENTAL BOTANY 2002; 53:939-945. [PMID: 11912236 DOI: 10.1093/jexbot/53.370.939] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The question of whether general control of amino acid synthesis exists in plants remains to be resolved. It is not known whether there is overall co-ordination of the biosynthesis of amino acids that are formed through distinct pathways. In this work, amino acid contents were measured in a large number of samples taken from wheat, potato and barley leaves under different photosynthetic conditions. The variability in total soluble amino acid contents between samples was approximately 6-fold in wheat and potato. Subtracting the major amino acids from the total soluble amino acids showed that the variability in summed minor amino acid contents was approximately 20-fold. This variability was not correlated with short-term changes in primary carbon and nitrogen metabolism, and only poorly correlated with total leaf amino acids. By contrast, striking linear relationships between the contents of most minor amino acids were observed, demonstrating that the contents of many minor amino acids vary in concert. These observations show that amino acid contents are co-ordinated across biosynthetic families. While these data might be interpreted as an indication of cross-pathway regulation of the expression of key biosynthetic enzymes, the impact of factors such as protein degradation and storage cannot be ignored.
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Affiliation(s)
- Graham Noctor
- Biochemistry and Physiology Department, IACR Rothamsted, Harpenden, Hertfordshire AL5 2JQ, UK.
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44
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Fischer WN, Loo DDF, Koch W, Ludewig U, Boorer KJ, Tegeder M, Rentsch D, Wright EM, Frommer WB. Low and high affinity amino acid H+-cotransporters for cellular import of neutral and charged amino acids. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2002; 29:717-31. [PMID: 12148530 DOI: 10.1046/j.1365-313x.2002.01248.x] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Amides and acidic amino acids represent the major long distance transport forms of organic nitrogen. Six amino acid permeases (AAPs) from Arabidopsis mediating transport of a wide spectrum of amino acids were isolated. AAPs are distantly related to plasma membrane amino acid transport systems N and A and to vesicular transporters such as VGAT from mammals. A detailed comparison of the properties by electrophysiology after heterologous expression in Xenopus oocytes shows that, although capable of recognizing and transporting a wide spectrum of amino acids, individual AAPs differ with respect to specificity. Apparent substrate affinities are influenced by structure and net charge and vary by three orders of magnitude. AAPs mediate cotransport of neutral amino acids with one proton. Uncharged forms of acidic and basic amino acids are cotransported with one proton. Since all AAPs are differentially expressed, different tissues may be supplied with a different spectrum of amino acids. AAP3 and AAP5 are the only transporters mediating efficient transport of the basic amino acids. In vivo competition shows that the capability to transport basic amino acids in planta might be overruled by excess amides and acidic amino acids in the apoplasm. With the exception of AAP6, AAPs do not recognize aspartate; only AAP6 has an affinity for aspartate in the physiologically relevant range. This property is due to an overall higher affinity of AAP6 for neutral and acidic amino acids. Thus AAP6 may serve a different role either in cooperating with the lower affinity systems to acquire amino acids in the low concentration range, as a system responsible for aspartate transport or as an uptake system from the xylem. In agreement, a yeast mutant deficient in acidic amino acid uptake at low aspartate concentrations was complemented only by AAP6. Taken together, the AAPs transport neutral, acidic and cationic amino acids, including the major transport forms, i.e. glutamine, asparagine and glutamate. Increasing proton concentrations strongly activate transport of amino acids. Thus the actual apoplasmic concentration of amino acids and the pH will determine what is transported in vivo, i.e. major amino acids such as glutamine, asparagine, and glutamate will be mobilized preferentially.
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Affiliation(s)
- Wolf-N Fischer
- Plant Physiology, Zentrum für Molekularbiologie der Pflanzen, Tübingen, Germany.
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Zeeman SC, Smith SM, Smith AM. The priming of amylose synthesis in Arabidopsis leaves. PLANT PHYSIOLOGY 2002; 128:1069-76. [PMID: 11891261 PMCID: PMC152218 DOI: 10.1104/pp.010640] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2001] [Revised: 10/16/2001] [Accepted: 11/28/2001] [Indexed: 05/20/2023]
Abstract
We investigated the mechanism of amylose synthesis in Arabidopsis leaves using (14)C-labeling techniques. First, we tested the hypothesis that short malto-oligosaccharides (MOS) may act as primers for granule-bound starch synthase I. We found increased amylose synthesis in isolated starch granules supplied with ADP[(14)C]glucose (ADP[(14)C]Glc) and MOS compared with granules supplied with ADP[(14)C]Glc but no MOS. Furthermore, using a MOS-accumulating mutant (dpe1), we found that more amylose was synthesized than in the wild type, correlating with the amount of MOS in vivo. When wild-type and mutant plants were tested in conditions where both lines had similar MOS contents, no difference in amylose synthesis was observed. We also tested the hypothesis that branches of amylopectin might serve as the primers for granule-bound starch synthase I. In this model, elongated branches of amylopectin are subsequently cleaved to form amylose. We conducted pulse-chase experiments, supplying a pulse of ADP[(14)C]Glc to isolated starch granules or (14)CO(2) to intact plants, followed by a chase period in unlabeled substrate. We detected no transfer of label from the amylopectin fraction to the amylose fraction of starch either in isolated starch granules or in intact leaves, despite varying the time course of the experiments and using a mutant line (sex4) in which high-amylose starch is synthesized. We therefore find no evidence for amylopectin-primed amylose synthesis in Arabidopsis. We propose that MOS are the primers for amylose synthesis in Arabidopsis leaves.
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Affiliation(s)
- Samuel C Zeeman
- Institute of Plant Sciences, University of Bern, Switzerland.
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46
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Farré EM, Tiessen A, Roessner U, Geigenberger P, Trethewey RN, Willmitzer L. Analysis of the compartmentation of glycolytic intermediates, nucleotides, sugars, organic acids, amino acids, and sugar alcohols in potato tubers using a nonaqueous fractionation method. PLANT PHYSIOLOGY 2001; 127:685-700. [PMID: 11598242 PMCID: PMC125103 DOI: 10.1104/pp.010280] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2001] [Revised: 05/29/2001] [Accepted: 06/22/2001] [Indexed: 05/17/2023]
Abstract
The compartmentation of metabolism in heterotrophic plant tissues is poorly understood due to the lack of data on metabolite distributions and fluxes between subcellular organelles. The main reason for this is the lack of suitable experimental methods with which intracellular metabolism can be measured. Here, we describe a nonaqueous fractionation method that allows the subcellular distributions of metabolites in developing potato (Solanum tuberosum L. cv Desiree) tubers to be calculated. In addition, we have coupled this fractionation method to a recently described gas chromatography-mass spectrometry procedure that allows the measurement of a wide range of small metabolites. To calculate the subcellular metabolite concentrations, we have analyzed organelle volumes in growing potato tubers using electron microscopy. The relative volume distributions in tubers are very similar to the ones for source leaves. More than 60% of most sugars, sugar alcohols, organic acids, and amino acids were found in the vacuole, although the concentrations of these metabolites is often higher in the cytosol. Significant amounts of the substrates for starch biosynthesis, hexose phosphates, and ATP were found in the plastid. However, pyrophosphate was located almost exclusively in the cytosol. Calculation of the mass action ratios of sucrose synthase, UDP-glucose pyrophosphorylase, phosphoglucosisomerase, and phosphoglucomutase indicate that these enzymes are close to equilibrium in developing potato tubers. However, due to the low plastidic pyrophosphate concentration, the reaction catalyzed by ADP-glucose pyrophosphorylase was estimated to be far removed from equilibrium.
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Affiliation(s)
- E M Farré
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Golm, Germany.
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Li X, Wanek W, Nehls U, Popp M, Hampp R, Rennenberg H, Einig W. Phosphoenolpyruvate carboxylase in mistletoe leaves: Regulation of gene expression, protein content, and covalent modification. PHYSIOLOGIA PLANTARUM 2001; 112:343-352. [PMID: 11473691 DOI: 10.1034/j.1399-3054.2001.1120307.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Seasonal changes in the activity of phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31), a key enzyme in the interaction of carbohydrate and nitrogen metabolism, were studied in leaves of the C3 semiparasitic mistletoe, Viscum album, growing on different host trees. Maximum extractable PEPCase activities were higher in leaves of mistletoes growing on Betula pendula and Alnus glutinosa hosts compared with those on the conifers, Abies alba and Larix decidua. Independent of host, maximum extractable PEPCase activities were high in spring and autumn while low in summer. Samples with higher PEPCase activities showed higher amounts of PEPCase protein and higher PEPCase mRNA levels. A curvilinear correlation between leaf total nitrogen content and the maximum extractable PEPCase activity as well as PEPCase mRNA level suggested that nitrogen might affect the activity of PEPCase of mistletoe by up-regulating gene expression. In addition to extractable activity, seasonal changes of the PEPCase activation state, the ratio of activities resulting from limited:non-limited assays, were found, which was correlated to the variation of malate content in leaves of mistletoe. ATP-dependent activation of PEPCase was characterized by an increase in I0.5(L-malate), indicating that PEPCase of leaves of mistletoes is probably regulated via phosphorylation.
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Affiliation(s)
- Xuemei Li
- Lehrstuhl für Physiologische Ökologie der Pflanzen, Universität Tübingen, Auf der Morgenstelle 1, D-72076, Tübingen, Germany; Institut für Ökologie und Naturschutz, Universität Wien, Althanstr. 14, POB 285, A-1091 Wien, Austria; Albert-Ludwigs-Universität Freiburg, Institut für Forstbotanik und Baumphysiologie, Professur für Baumphysiologie, Am Flughafen 17, D-79110 Freiburg i. Br., Germany
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48
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Polle A. Dissecting the superoxide dismutase-ascorbate-glutathione-pathway in chloroplasts by metabolic modeling. Computer simulations as a step towards flux analysis. PLANT PHYSIOLOGY 2001; 126:445-62. [PMID: 11351106 PMCID: PMC102317 DOI: 10.1104/pp.126.1.445] [Citation(s) in RCA: 194] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2000] [Revised: 12/15/2000] [Accepted: 02/14/2001] [Indexed: 05/18/2023]
Abstract
The present study introduces metabolic modeling as a new tool to analyze the network of redox reactions composing the superoxide dismutase-ascorbate (Asc)-glutathione (GSH) cycle. Based on previously determined concentrations of antioxidants and defense enzymes in chloroplasts, kinetic properties of antioxidative enzymes, and nonenzymatic rate constants of antioxidants with reactive oxygen, models were constructed to simulate oxidative stress and calculate changes in concentrations and fluxes of oxidants and antioxidants. Simulated oxidative stress in chloroplasts did not result in a significant accumulation of O2*- and H2O2 when the supply with reductant was sufficient. Model results suggest that the coupling between Asc- and GSH-related redox systems was weak because monodehydroascorbate radical reductase prevented dehydroascorbate (DHA) formation efficiently. DHA reductase activity was dispensable. Glutathione reductase was mainly required for the recycling of GSH oxidized in nonenzymatic reactions. In the absence of monodehydroascorbate radical reductase and DHA reductase, glutathione reductase and GSH were capable to maintain the Asc pool more than 99% reduced. This suggests that measured DHA/Asc ratios do not reflect a redox balance related to the Asc-GSH-cycle. Decreases in Asc peroxidase resulted in marked H2O2 accumulation without significant effects on the redox balance of Asc/DHA or GSH/GSSG. Simulated loss of SOD resulted in higher H2O2 production rates, thereby affecting all subsequent steps of the Asc-GSH-cycle. In conclusion, modeling approaches contribute to the theoretical understanding of the functioning of antioxidant systems by pointing out questions that need to be validated and provide additional information that is useful to develop breeding strategies for higher stress resistance in plants.
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Affiliation(s)
- A Polle
- Georg-August Universitaet, Forstbotanisches Institut, Abteilung I, Forstbotanik und Baumphysiologie, Buesgenweg 2, 37077 Goettingen, Germany.
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49
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Lohaus G, Pennewiss K, Sattelmacher B, Hussmann M, Hermann Muehling K. Is the infiltration-centrifugation technique appropriate for the isolation of apoplastic fluid? A critical evaluation with different plant species. PHYSIOLOGIA PLANTARUM 2001; 111:457-465. [PMID: 11299010 DOI: 10.1034/j.1399-3054.2001.1110405.x] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The suitability of the infiltration-centrifugation method for collection of apoplastic fluid from intact leaves was evaluated for different plant species. Large differences with respect to infiltrability of the leaves, which correlated inversely with stomatal and mesophyll resistance, became apparent. Osmolality of infiltration medium (deionised water, 0.2 mM CaCl2, 10 mM KCl, 180 mM 2-[N-morpholino]ethane-sulphonic acid) and incubation time, time passed between onset of infiltration and end of centrifugation, revealed relatively little influence on the composition of the apoplastic washing fluid (AWF). In contrast, the pH of the infiltrated solution highly influenced the concentration of sucrose and hexoses. With increasing centrifugation force, hexosephosphate isomerase (HPI) activity in the AWF, which was taken as an indication for cytoplasmic contamination, increased. At the same time, Ca2+ concentration in the AWF increased even more. Since Ca2+ cannot originate from the cytoplasm, the suitability of HPI as marker for cytoplasmic contamination is questioned. From the composition of the AWF, it is concluded that, if centrifugation force does not exceed 1 000 g, cytoplasmic contamination is negligible and that the infiltration-centrifugation technique reveals an easy and inexpensive way to study apoplastic solutes. The infiltration-centrifugation method was also suitable to determine apoplastic air volume (Vair) and apoplastic water volume (Vwater), which are necessary for the calculation of the ion concentration in the leaf apoplast. It could be shown that the leaves of different species and the apical and basal leaves of single plants differ in Vair and Vwater.
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Affiliation(s)
- Gertrud Lohaus
- Albrecht-von-Haller Institut für Pflanzenwissenschaften, Biochemie der Pflanze, Untere Karspüle 2, D-37073 Goettingen, Germany; Institute for Plant Nutrition and Soil Science, Christian-Albrechts University, Olshausenstrasse 40, D-24098 Kiel, Germany; Present address: University of California, Department of Land, Air and Water Resources, One Shields Avenue, Davis, California 95616-8627, USA
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50
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Sattelmacher B. The apoplast and its significance for plant mineral nutrition. THE NEW PHYTOLOGIST 2001; 149:167-192. [PMID: 33874640 DOI: 10.1046/j.1469-8137.2001.00034.x] [Citation(s) in RCA: 188] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It has only recently become apparent that the apoplast plays a major role in a diverse range of processes, including intercellular signalling, plant-microbe interactions and both water and nutrient transport. Broadly defined, the apoplast constitutes all compartments beyond the plasmalemma - the interfibrillar and intermicellar space of the cell walls, and the xylem, including its gas- and water-filled intercellular space - extending to the rhizoplane and cuticle of the outer plant surface. The physico-chemical properties of cell walls influence plant mineral nutrition, as nutrients do not simply pass through the apoplast to the plasmalemma but can also be adsorbed or fixed to cell-wall components. Here, current progress in understanding the significance of the apoplast in plant mineral nutrition is reviewed. The contribution of the root apoplast to short-distance transport and nutrient uptakes is examined particularly in relation to Na+ toxicity and Al3+ tolerance. The review extends to long-distance transport and the role of the apoplast as a habitat for microorganisms. In the leaf, the apoplast might have benefits over the vacuole as a site for short-term nutrient storage and solute exchange with the atmosphere. Contents Summary 167 I. Introduction 168 II. The properties of the apoplast and its implication for solute movement 168 1. The middle lamella 168 2. The primary wall 168 3. The secondary cell wall 169 III. The root apoplast - nutrient uptake and short-distance transport 170 IV. The apoplast as a compartment for long distance transport 174 V. The apoplast - habitat for microorganisms 175 VI. The apoplast of leaves - a compartment of storage and of reactions 177 1. Transport routes in the leaf apoplast 177 2. Methods of studying apoplastic solutes 177 3. Solute relations in the leaf apoplast 178 4. Concentration gradients in the leaf apoplast 179 5. Ion relations in the leaf apoplast and symptoms of deficiency and toxicity 179 6. Ion relations in the leaf apoplast - influence of nutrient supply 180 7. The leaf apoplast - compartment for transient ion storage 180 8. Ion fluxes between apoplast and symplast 181 9. Apoplastic ion balance 181 10. Leaf apoplast - interaction with the atmosphere 183 VII. Conclusions 183 Acknowledgements 183 References 183.
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Affiliation(s)
- Burkhard Sattelmacher
- Institute for Plant Nutrition and Soil Science, University Kiel, Oshausenstr. 40 D-24118 Kiel, Germany
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