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Abadie C, Lalande J, Dourmap C, Limami AM, Tcherkez G. Leaf day respiration involves multiple carbon sources and depends on previous dark metabolism. PLANT, CELL & ENVIRONMENT 2024; 47:2146-2162. [PMID: 38444114 DOI: 10.1111/pce.14871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 02/06/2024] [Accepted: 02/20/2024] [Indexed: 03/07/2024]
Abstract
Day respiration (Rd) is the metabolic, nonphotorespiratory process by which illuminated leaves liberate CO2 during photosynthesis. Rd is used routinely in photosynthetic models and is thus critical for calculations. However, metabolic details associated with Rd are poorly known, and this can be problematic to predict how Rd changes with environmental conditions and relates to night respiration. It is often assumed that day respiratory CO2 release just reflects 'ordinary' catabolism (glycolysis and Krebs 'cycle'). Here, we carried out a pulse-chase experiment, whereby a 13CO2 pulse in the light was followed by a chase period in darkness and then in the light. We took advantage of nontargeted, isotope-assisted metabolomics to determine non-'ordinary' metabolism, detect carbon remobilisation and compare light and dark 13C utilisation. We found that several concurrent metabolic pathways ('ordinary' catabolism, oxidative pentose phosphates pathway, amino acid production, nucleotide biosynthesis and secondary metabolism) took place in the light and participated in net CO2 efflux associated with day respiration. Flux reconstruction from metabolomics leads to an underestimation of Rd, further suggesting the contribution of a variety of CO2-evolving processes. Also, the cornerstone of the Krebs 'cycle', citrate, is synthetised de novo from photosynthates mostly in darkness, and remobilised or synthesised from stored material in the light. Collectively, our data provides direct evidence that leaf day respiration (i) involves several CO2-producing reactions and (ii) is fed by different carbon sources, including stored carbon disconnected from current photosynthates.
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Affiliation(s)
- Cyril Abadie
- Institut de recherche en horticulture et semences, INRAe, Université d'Angers, Beaucouzé, France
- Ecophysiologie et génomique fonctionnelle de la vigne, Institut des Sciences de la Vigne et du Vin, INRAe, Université de Bordeaux, Villenave-d'Ornon, France
| | - Julie Lalande
- Institut de recherche en horticulture et semences, INRAe, Université d'Angers, Beaucouzé, France
| | - Corentin Dourmap
- Institut de recherche en horticulture et semences, INRAe, Université d'Angers, Beaucouzé, France
| | - Anis M Limami
- Institut de recherche en horticulture et semences, INRAe, Université d'Angers, Beaucouzé, France
| | - Guillaume Tcherkez
- Institut de recherche en horticulture et semences, INRAe, Université d'Angers, Beaucouzé, France
- Research School of Biology, ANU College of Science, Australian National University, Canberra, Australia
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2
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Gai W, Yuan L, Yang F, Ahiakpa JK, Li F, Ge P, Zhang X, Tao J, Wang F, Yang Y, Zhang Y. Genome-wide variants and optimal allelic combinations for citric acid in tomato. HORTICULTURE RESEARCH 2024; 11:uhae070. [PMID: 38725459 PMCID: PMC11079488 DOI: 10.1093/hr/uhae070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 02/25/2024] [Indexed: 05/12/2024]
Abstract
Citric acid (CA) plays a crucial role as a fruit flavor enhancer and serves as a mediator in multiple metabolic pathways in tomato fruit development. Understanding factors influencing CA metabolism is essential for enhancing fruit flavor and CA-mediated biological processes. The accumulation of CA, however, is influenced by a complex interplay of genetic and environmental factors, leading to challenges in accurately predicting and regulating its levels. In this study, we conducted a genome-wide association study (GWAS) on CA, employing six landmark models based on genome-wide variations including structural variants, insertions and deletions, and single nucleotide polymorphisms. The identification of 11 high-confidence candidate genes was further facilitated by leveraging linkage disequilibrium and causal variants associated with CA. The transcriptome data from candidate genes were examined, revealing higher correlations between the expression of certain candidate genes and changes in CA metabolism. Three CA-associated genes exerted a positive regulatory effect on CA accumulation, while the remaining genes exhibited negative impacts based on gene cluster and correlation analyses. The CA content of tomatoes is primarily influenced by improvement sweeps with minimal influence from domestication sweeps in the long-term breeding history, as evidenced by population differentiation and variants distribution. The presence of various causal variants within candidate genes is implicated in the heterogeneity of CA content observed among the tomato accessions. This observation suggests a potential correlation between the number of alternative alleles and CA content. This study offers significant function-based markers that can be utilized in marker-assisted breeding, thereby enhancing their value and applicability.
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Affiliation(s)
- Wenxian Gai
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Liangdan Yuan
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Fan Yang
- College of Horticulture, Northwest A&F University, Yangling 712100, China
| | - John Kojo Ahiakpa
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Fangman Li
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Pingfei Ge
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Xingyu Zhang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Jinbao Tao
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Fei Wang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Yang Yang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
| | - Yuyang Zhang
- National Key Laboratory for Germplasm Innovation & Utilization of Horticultural Crops, Huazhong Agricultural University, Wuhan 430070, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
- Shenzhen Institute of Nutrition and Health, Huazhong Agricultural University, Wuhan 430070, China
- Shenzhen Branch, Guangdong Laboratory for Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen 518000, China
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Burgos A, Miranda E, Vilaprinyo E, Meza-Canales ID, Alves R. CAM Models: Lessons and Implications for CAM Evolution. FRONTIERS IN PLANT SCIENCE 2022; 13:893095. [PMID: 35812979 PMCID: PMC9260309 DOI: 10.3389/fpls.2022.893095] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
The evolution of Crassulacean acid metabolism (CAM) by plants has been one of the most successful strategies in response to aridity. On the onset of climate change, expanding the use of water efficient crops and engineering higher water use efficiency into C3 and C4 crops constitute a plausible solution for the problems of agriculture in hotter and drier environments. A firm understanding of CAM is thus crucial for the development of agricultural responses to climate change. Computational models on CAM can contribute significantly to this understanding. Two types of models have been used so far. Early CAM models based on ordinary differential equations (ODE) reproduced the typical diel CAM features with a minimal set of components and investigated endogenous day/night rhythmicity. This line of research brought to light the preponderant role of vacuolar malate accumulation in diel rhythms. A second wave of CAM models used flux balance analysis (FBA) to better understand the role of CO2 uptake in flux distribution. They showed that flux distributions resembling CAM metabolism emerge upon constraining CO2 uptake by the system. We discuss the evolutionary implications of this and also how CAM components from unrelated pathways could have integrated along evolution.
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Affiliation(s)
- Asdrubal Burgos
- Laboratorio de Biotecnología, CUCBA, Universidad de Guadalajara, Guadalajara, Mexico
| | - Enoc Miranda
- Laboratorio de Biotecnología, CUCBA, Universidad de Guadalajara, Guadalajara, Mexico
| | - Ester Vilaprinyo
- Institute of Biomedical Research of Lleida, IRBLleida, Lleida, Spain
- Departament de Ciències Mèdiques Bàsiques, Universitat de Lleida, Lleida, Spain
| | - Iván David Meza-Canales
- Departamento de Ecología Aplicada, CUCBA, Universidad de Guadalajara, Guadalajara, Mexico
- Unidad de Biología Molecular, Genómica y Proteómica, ITRANS-CUCEI, Universidad de Guadalajara, Guadalajara, Mexico
| | - Rui Alves
- Institute of Biomedical Research of Lleida, IRBLleida, Lleida, Spain
- Departament de Ciències Mèdiques Bàsiques, Universitat de Lleida, Lleida, Spain
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Dondini L, Domenichini C, Dong Y, Gennari F, Bassi D, Foschi S, Lama M, Adami M, De Franceschi P, Cervellati C, Bergonzoni L, Alessandri S, Tartarini S. Quantitative Trait Loci Mapping and Identification of Candidate Genes Linked to Fruit Acidity in Apricot ( Prunus armeniaca L.). FRONTIERS IN PLANT SCIENCE 2022; 13:838370. [PMID: 35371156 PMCID: PMC8972129 DOI: 10.3389/fpls.2022.838370] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 02/14/2022] [Indexed: 06/14/2023]
Abstract
Apricot breeding programs could be strongly improved by the availability of molecular markers linked to the main fruit quality traits. Fruit acidity is one of the key factors in consumer acceptance, but despite its importance, the molecular bases of this trait are still poorly understood. In order to increase the genetic knowledge on the fruit acidity, an F1 apricot population ('Lito' × 'BO81604311') has been phenotyped for titratable acidity and juice pH for the three following years. In addition, the contents of the main organic acids of the juice (malate, citrate, and quinate) were also evaluated. A Gaussian distribution was observed for most of the traits in this progeny, confirming their quantitative inheritance. An available simple sequence repeat (SSR)-based molecular map, implemented with new markers in specific genomic regions, was used to perform a quantitative trait loci (QTL) analysis. The molecular map was also anchored to the recently published apricot genome sequence of 'Stella.' Several major QTLs linked to fruit acidity-related traits have been identified both in the 'Lito' (no. 21) and 'BO81604311' (no. 13), distributed in five linkage groups (LG 4, 5, 6, 7, and 8). Some of these QTLs show good stability between years and their linked markers were used to identify candidate genes in specific QTLs genomic regions.
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Affiliation(s)
- Luca Dondini
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Cecilia Domenichini
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Yonghui Dong
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Fabio Gennari
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Daniele Bassi
- Department of Agricultural and Environmental Sciences (DISAA), University of Milan, Milan, Italy
| | | | | | - Marco Adami
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Paolo De Franceschi
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Claudia Cervellati
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Lorenzo Bergonzoni
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Sara Alessandri
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
| | - Stefano Tartarini
- Department of Agricultural and Food Sciences, Alma Mater Studiorum – University of Bologna, Bologna, Italy
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5
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Huang XY, Wang CK, Zhao YW, Sun CH, Hu DG. Mechanisms and regulation of organic acid accumulation in plant vacuoles. HORTICULTURE RESEARCH 2021; 8:227. [PMID: 34697291 PMCID: PMC8546024 DOI: 10.1038/s41438-021-00702-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/09/2021] [Accepted: 09/24/2021] [Indexed: 06/13/2023]
Abstract
In fleshy fruits, organic acids are the main source of fruit acidity and play an important role in regulating osmotic pressure, pH homeostasis, stress resistance, and fruit quality. The transport of organic acids from the cytosol to the vacuole and their storage are complex processes. A large number of transporters carry organic acids from the cytosol to the vacuole with the assistance of various proton pumps and enzymes. However, much remains to be explored regarding the vacuolar transport mechanism of organic acids as well as the substances involved and their association. In this review, recent advances in the vacuolar transport mechanism of organic acids in plants are summarized from the perspectives of transporters, channels, proton pumps, and upstream regulators to better understand the complex regulatory networks involved in fruit acid formation.
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Affiliation(s)
- Xiao-Yu Huang
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China
| | - Chu-Kun Wang
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China
| | - Yu-Wen Zhao
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China
| | - Cui-Hui Sun
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China.
| | - Da-Gang Hu
- National Key Laboratory of Crop Biology; Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production; College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China.
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6
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Igamberdiev AU. Citrate valve integrates mitochondria into photosynthetic metabolism. Mitochondrion 2020; 52:218-230. [PMID: 32278088 DOI: 10.1016/j.mito.2020.04.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 03/21/2020] [Accepted: 04/07/2020] [Indexed: 12/31/2022]
Abstract
While in heterotrophic cells and in darkness mitochondria serve as main producers of energy, during photosynthesis this function is transferred to chloroplasts and the main role of mitochondria in bioenergetics turns to be the balance of the level of phosphorylation of adenylates and of reduction of pyridine nucleotides to avoid over-energization of the cell and optimize major metabolic fluxes. This is achieved via the establishment and regulation of local equilibria of the tricarboxylic acid (TCA) cycle enzymes malate dehydrogenase and fumarase in one branch and aconitase and isocitrate dehydrogenase in another branch. In the conditions of elevation of redox level, the TCA cycle is transformed into a non-cyclic open structure (hemicycle) leading to the export of the tricarboxylic acid (citrate) to the cytosol and to the accumulation of the dicarboxylic acids (malate and fumarate). While the buildup of NADPH in chloroplasts provides operation of the malate valve leading to establishment of NADH/NAD+ ratios in different cell compartments, the production of NADH by mitochondria drives citrate export by establishing conditions for the operation of the citrate valve. The latter regulates the intercompartmental NADPH/NADP+ ratio and contributes to the biosynthesis of amino acids and other metabolic products during photosynthesis.
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Affiliation(s)
- Abir U Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John's, NL A1B 3X9, Canada.
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7
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Stevens GG, Pérez-Fernández MA, Morcillo RJL, Kleinert A, Hills P, Brand DJ, Steenkamp ET, Valentine AJ. Roots and Nodules Response Differently to P Starvation in the Mediterranean-Type Legume Virgilia divaricata. FRONTIERS IN PLANT SCIENCE 2019; 10:73. [PMID: 30804964 PMCID: PMC6370976 DOI: 10.3389/fpls.2019.00073] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Accepted: 01/17/2019] [Indexed: 06/09/2023]
Abstract
Virgilia divaricata is a tree legume that grows in the Cape Floristic Region (CFA) in poor nutrient soils. A comparison between high and low phosphate growth conditions between roots and nodules was conducted and evaluated for the plants ability to cope under low phosphate stress conditions in V. divaricata. We proved that the plant copes with low phosphate stress through an increased allocation of resources, reliance on BNF and enhanced enzyme activity, especially PEPC. Nodules had a lower percentage decline in P compared to roots to uphold its metabolic functions. These strategies partly explain how V. divaricata can sustain growth despite LP conditions. Although the number of nodules declined with LP, their biomass remained unchanged in spite of a plant decline in dry weight. This is achieved via the high efficiency of BNF under P stress. During LP, nodules had a lower % decline at 34% compared to the roots at 88%. We attribute this behavior to P conservation strategies in LP nodules that imply an increase in a metabolic bypass that operates at the PEP branch point in glycolysis. The enhanced activities of nodule PEPC, MDH, and ME, whilst PK declines, suggests that under LP conditions an adenylate bypass was in operation either to synthesize more organic acids or to mediate pyruvate via a non-adenylate requiring metabolic route. Both possibilities represent a P-stress adaptation route and this is the first report of its kind for legume trees that are indigenous to low P, acid soils. Although BNF declined by a small percentage during LP, this P conservation was evident in the unchanged BNF efficiency per weight, and the increase in BNF efficiency per mol of P. It appears that legumes that are indigenous to acid soils, may be able to continue their reliance on BNF via increased allocation to nodules and also due to increase their efficiency for BNF on a P basis, owing to P-saving mechanisms such as the organic acid routes.
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Affiliation(s)
- Gary G. Stevens
- Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa
| | | | - Rafael J. L. Morcillo
- Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai, China
| | - Aleysia Kleinert
- Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa
| | - Paul Hills
- Institute for Plant Biotechnology, Stellenbosch University, Matieland, South Africa
| | - D. Jacobus Brand
- NMR Unit, Central Analytical Facility, Stellenbosch University, Matieland, South Africa
| | - Emma T. Steenkamp
- Department of Microbiology and Plant Pathology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria, South Africa
| | - Alex J. Valentine
- Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa
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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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9
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Zhang W, Zhang X, Wang Y, Zhang N, Guo Y, Ren X, Zhao Z. Potassium fertilization arrests malate accumulation and alters soluble sugar metabolism in apple fruit. Biol Open 2018; 7:bio024745. [PMID: 30404903 PMCID: PMC6310881 DOI: 10.1242/bio.024745] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 10/31/2018] [Indexed: 12/28/2022] Open
Abstract
Effects of different potassium (K) levels, which were K0 (no fertilizer), K1 (71.5 g KCl plant-1 year-1), K2 (286.7 g KCl plant-1 year-1), and K3 (434 g KCl plant-1 year-1), were evaluated based on sugar and organic acid metabolism levels from 70-126 days after bloom (DAB) in the developing fruit of potted five-year-old apple (Malus domestica, Borkh.) trees. The results indicate that K fertilization promoted greater fruit mass, higher Ca2+ and soluble solid levels, and lower titratable acid levels, as well as increased pH values at harvest. With the application of different levels of K fertilizer, fructose, sorbitol, glucose and sucrose accumulation rates significantly changed during fruit development. Fruit in the K2 group had higher fructose, sucrose and glucose levels than those in other treatment groups at 126 DAB. These changes in soluble sugar are related to the activity of metabolic enzymes. Sucrose synthase (SS) and sorbitol dehydrogenase (SDH) activity in the K2 treated fruit was significantly higher than those in other treatment groups from 70-126 DAB. Malate levels in K-supplemented fruit were notably lower than those in non K-supplemented fruit, and K3 treated fruit had the lowest malate levels during fruit development. Cytosolic malic enzyme (ME) and phosphoenolpyruvate carboxykinase (PEPCK) activity significantly increased in fruit under the K2 treatment during 112-126 DAB and 98-126 DAB, respectively. In addition, Ca2+ concentration increased with increasing K fertilization levels, which promoted a maximum of 11.72 mg g-1 dry weight in apple fruit. These results show that K levels can alter soluble sugar and malate levels due to the interaction between sugars and acid-metabolic enzymes in fruit.
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Affiliation(s)
- Wen Zhang
- College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Xian Zhang
- College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Yufei Wang
- College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Nishang Zhang
- Key Laboratory of Horticulture Plant Biology and Germplasm Innovation in Northwest China, Ministry of Agriculture, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Yanping Guo
- College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China
- Key Laboratory of Horticulture Plant Biology and Germplasm Innovation in Northwest China, Ministry of Agriculture, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Xiaolin Ren
- College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, China
| | - Zhengyang Zhao
- Shaanxi Engineering Research Center for Apple, Northwest A&F University, Yangling 712100, Shaanxi, China
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10
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Ting MKY, She YM, Plaxton WC. Transcript profiling indicates a widespread role for bacterial-type phosphoenolpyruvate carboxylase in malate-accumulating sink tissues. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:5857-5869. [PMID: 29240945 PMCID: PMC5854131 DOI: 10.1093/jxb/erx399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Phosphoenolpyruvate carboxylase (PEPC) is an important regulatory enzyme situated at a key branch point of central plant metabolism. Plant genomes encode several plant-type PEPC (PTPC) isozymes, along with a distantly related bacterial-type PEPC (BTPC). BTPC is expressed at high levels in developing castor oil seeds where it tightly interacts with co-expressed PTPC polypeptides to form unusual hetero-octameric Class-2 PEPC complexes that are desensitized to allosteric inhibition by L-malate. Analysis of RNA-Seq and microarray transcriptome datasets revealed two distinct patterns of tissue-specific BTPC expression in vascular plants. Species such as Arabidopsis thaliana, strawberry, rice, maize, and poplar mainly exhibited pollen- or floral-specific BTPC expression. By contrast, BTPC transcripts were relatively abundant in developing castor, cotton, and soybean seeds, cassava tubers, as well as immature tomato, cucumber, grape, and avocado fruit. Immunoreactive 118 kDa BTPC polypeptides were detected on immunoblots of cucumber and tomato fruit extracts. Co-immunoprecipitation established that as in castor, BTPCs physically interact with endogenous PTPCs to form Class-2 PEPC complexes in tomato and cucumber fruit. We hypothesize that Class-2 PEPCs simultaneously maintain rapid anaplerotic PEP carboxylation and respiratory CO2 refixation in diverse, biosynthetically active sinks that accumulate high malate levels.
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Affiliation(s)
- Michael K Y Ting
- Department of Biology, Queen’s University, Kingston, Ontario, Canada
| | - Yi-Min She
- Centre for Biologics Evaluation Biologics and Genetic Therapies Directorate, Health Canada, Ottawa, Ontario, Canada
| | - William C Plaxton
- Department of Biology, Queen’s University, Kingston, Ontario, Canada
- Department of Biomedical and Molecular Sciences, Queen’s University, Kingston, Ontario, Canada
- Correspondence:
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11
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Abadie C, Lothier J, Boex-Fontvieille E, Carroll A, Tcherkez G. Direct assessment of the metabolic origin of carbon atoms in glutamate from illuminated leaves using 13 C-NMR. THE NEW PHYTOLOGIST 2017; 216:1079-1089. [PMID: 28771732 DOI: 10.1111/nph.14719] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 06/25/2017] [Indexed: 05/21/2023]
Abstract
Glutamate (Glu) is the cornerstone of nitrogen assimilation and photorespiration in illuminated leaves. Despite this crucial role, our knowledge of the flux to Glu de novo synthesis is rather limited. Here, we used isotopic labelling with 13 CO2 and 13 C-NMR analyses to examine the labelling pattern and the appearance of multi-labelled species of Glu molecules to trace the origin of C-atoms found in Glu. We also compared this with 13 C-labelling patterns in Ala and Asp, which reflect citrate (and thus Glu) precursors, that is, pyruvate and oxaloacetate. Glu appeared to be less 13 C-labelled than Asp and Ala, showing that the Glu pool was mostly formed by 'old' carbon atoms. There were modest differences in intramolecular 13 C-13 C couplings between Glu C-2 and Asp C-3, showing that oxaloacetate metabolism to Glu biosynthesis did not involve C-atom redistribution by the Krebs cycle. The apparent carbon allocation increased with carbon net photosynthesis. However, when expressed relative to CO2 fixation, it was clearly higher at low CO2 while it did not change in 2% O2 , as compared to standard conditions. We conclude that Glu production from current photosynthetic carbon represents a small flux that is controlled by the gaseous environment, typically upregulated at low CO2 .
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Affiliation(s)
- Cyril Abadie
- Research School of Biology, College of Medicine, Biology and Environment, Australian National University, Canberra, ACT, 2601, Australia
| | - Jérémy Lothier
- IRHS, Agrocampus-Ouest, INRA, Université d'Angers, SFR 4207 QuaSaV, 42 Rue Georges Morel, Beaucouzé, 49071, France
| | - Edouard Boex-Fontvieille
- Laboratoire de Police Scientifique de Lyon, Institut National de Police Scientifique, 31 Avenue Franklin Roosevelt, Écully Cedex, 69134, France
| | - Adam Carroll
- Research School of Biology, College of Medicine, Biology and Environment, Australian National University, Canberra, ACT, 2601, Australia
| | - Guillaume Tcherkez
- Research School of Biology, College of Medicine, Biology and Environment, Australian National University, Canberra, ACT, 2601, Australia
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12
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Hu DG, Li YY, Zhang QY, Li M, Sun CH, Yu JQ, Hao YJ. The R2R3-MYB transcription factor MdMYB73 is involved in malate accumulation and vacuolar acidification in apple. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 91:443-454. [PMID: 28423209 DOI: 10.1111/tpj.13579] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 04/07/2017] [Accepted: 04/12/2017] [Indexed: 05/19/2023]
Abstract
Malate, the predominant organic acid in many fruits, is a crucial component of the organoleptic quality of fruit, including taste and flavor. The genetic and environmental mechanisms affecting malate metabolism in fruit cells have been studied extensively. However, the transcriptional regulation of malate-metabolizing enzymes and vacuolar transporters remains poorly understood. Our previous studies demonstrated that MdMYB1 modulates anthocyanin accumulation and vacuolar acidification by directly activating vacuolar transporters, including MdVHA-B1, MdVHA-E, MdVHP1 and MdtDT. Interestingly, we isolated and identified a MYB transcription factor, MdMYB73, a distant relative of MdMYB1 in this study. It was subsequently found that MdMYB73 protein bound directly to the promoters of MdALMT9 (aluminum-activated malate transporter 9), MdVHA-A (vacuolar ATPase subunit A) and MdVHP1 (vacuolar pyrophosphatase 1), transcriptionally activating their expression and thereby enhancing their activities. Analyses of transgenic apple calli demonstrated that MdMYB73 influenced malate accumulation and vacuolar pH. Furthermore, MdCIbHLH1 interacted with MdMYB73 and enhanced its activity upon downstream target genes. These findings help to elucidate how MdMYB73 directly modulates the vacuolar transport system to affect malate accumulation and vacuolar pH in apple.
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Affiliation(s)
- Da-Gang Hu
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, 271018, China
| | - Yuan-Yuan Li
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, 271018, China
| | - Quan-Yan Zhang
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, 271018, China
| | - Ming Li
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, 271018, China
| | - Cui-Hui Sun
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, 271018, China
| | - Jian-Qiang Yu
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, 271018, China
| | - Yu-Jin Hao
- National Key Laboratory of Crop Biology, MOA Key Laboratory of Horticultural Crop Biology and Germplasm Innovation, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai-An, Shandong, 271018, China
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13
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Misra BB, Yin Z, Geng S, de Armas E, Chen S. Metabolomic Responses of Arabidopsis Suspension Cells to Bicarbonate under Light and Dark Conditions. Sci Rep 2016; 6:35778. [PMID: 27762345 PMCID: PMC5071901 DOI: 10.1038/srep35778] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 10/05/2016] [Indexed: 11/25/2022] Open
Abstract
Global CO2 level presently recorded at 400 ppm is expected to reach 550 ppm in 2050, an increment likely to impact plant growth and productivity. Using targeted LC-MS and GC-MS platforms we quantified 229 and 29 metabolites, respectively in a time-course study to reveal short-term responses to different concentrations (1, 3, and 10 mM) of bicarbonate (HCO3−) under light and dark conditions. Results indicate that HCO3− treatment responsive metabolomic changes depend on the HCO3− concentration, time of treatment, and light/dark. Interestingly, 3 mM HCO3− concentration treatment induced more significantly changed metabolites than either lower or higher concentrations used. Flavonoid biosynthesis and glutathione metabolism were common to both light and dark-mediated responses in addition to showing concentration-dependent changes. Our metabolomics results provide insights into short-term plant cellular responses to elevated HCO3− concentrations as a result of ambient increases in CO2 under light and dark.
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Affiliation(s)
- Biswapriya B Misra
- Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32610, USA
| | - Zepeng Yin
- Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32610, USA.,Alkali Soil Natural Environmental Science Center, Northeast Forestry University, Key Laboratory of Saline-alkali Vegetation Ecology Restoration in Oil Field, Ministry of Education, Harbin 150040, China
| | - Sisi Geng
- Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32610, USA
| | - Evaldo de Armas
- Training Institute, Thermo Fisher Scientific, 1400 North point Parkway, Ste 10., West Palm Beach, FL 33407, USA
| | - Sixue Chen
- Department of Biology, Genetics Institute, Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32610, USA.,Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL 32610, USA
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Lehmann MM, Wegener F, Werner RA, Werner C. Diel variations in carbon isotopic composition and concentration of organic acids and their impact on plant dark respiration in different species. PLANT BIOLOGY (STUTTGART, GERMANY) 2016; 18:776-84. [PMID: 27086877 DOI: 10.1111/plb.12464] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 04/13/2016] [Indexed: 05/19/2023]
Abstract
Leaf respiration in the dark and its C isotopic composition (δ(13) CR ) contain information about internal metabolic processes and respiratory substrates. δ(13) CR is known to be less negative compared to potential respiratory substrates, in particular shortly after darkening during light enhanced dark respiration (LEDR). This phenomenon might be driven by respiration of accumulated (13) C-enriched organic acids, however, studies simultaneously measuring δ(13) CR during LEDR and potential respiratory substrates are rare. We determined δ(13) CR and respiration rates (R) during LEDR, as well as δ(13) C and concentrations of potential respiratory substrates using compound-specific isotope analyses. The measurements were conducted throughout the diel cycle in several plant species under different environmental conditions. δ(13) CR and R patterns during LEDR were strongly species-specific and showed an initial peak, which was followed by a progressive decrease in both values. The species-specific differences in δ(13) CR and R during LEDR may be partially explained by the isotopic composition of organic acids (e.g., oxalate, isocitrate, quinate, shikimate, malate), which were (13) C-enriched compared to other respiratory substrates (e.g., sugars and amino acids). However, the diel variations in both δ(13) C and concentrations of the organic acids were generally low. Thus, additional factors such as the heterogeneous isotope distribution in organic acids and the relative contribution of the organic acids to respiration are required to explain the strong (13) C enrichment in leaf dark-respired CO2 .
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Affiliation(s)
- M M Lehmann
- Laboratory of Atmospheric Chemistry, Paul Scherrer Institute (PSI), Villigen, Switzerland
- Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland
| | - F Wegener
- Ecosystem Physiology, University Freiburg, Freiburg, Germany
| | - R A Werner
- Institute of Agricultural Sciences, ETH Zurich, Zurich, Switzerland
| | - C Werner
- Ecosystem Physiology, University Freiburg, Freiburg, Germany
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15
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The evolution of citrate metabolism in acidic and acidless citrus genotypes during fruit development and ripening. ACTA ACUST UNITED AC 2016. [DOI: 10.17660/actahortic.2016.1135.7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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16
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Lehmann MM, Wegener F, Barthel M, Maurino VG, Siegwolf RTW, Buchmann N, Werner C, Werner RA. Metabolic Fate of the Carboxyl Groups of Malate and Pyruvate and their Influence on δ(13)C of Leaf-Respired CO2 during Light Enhanced Dark Respiration. FRONTIERS IN PLANT SCIENCE 2016; 7:739. [PMID: 27375626 PMCID: PMC4891945 DOI: 10.3389/fpls.2016.00739] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Accepted: 05/13/2016] [Indexed: 05/03/2023]
Abstract
The enhanced CO2 release of illuminated leaves transferred into darkness, termed "light enhanced dark respiration (LEDR)", is often associated with an increase in the carbon isotope ratio of the respired CO2 (δ(13)CLEDR). The latter has been hypothesized to result from different respiratory substrates and decarboxylation reactions in various metabolic pathways, which are poorly understood so far. To provide a better insight into the underlying metabolic processes of δ(13)CLEDR, we fed position-specific (13)C-labeled malate and pyruvate via the xylem stream to leaves of species with high and low δ(13)CLEDR values (Halimium halimifolium and Oxalis triangularis, respectively). During respective label application, we determined label-derived leaf (13)CO2 respiration using laser spectroscopy and the (13)C allocation to metabolic fractions during light-dark transitions. Our results clearly show that both carboxyl groups (C-1 and C-4 position) of malate similarly influence respiration and metabolic fractions in both species, indicating possible isotope randomization of the carboxyl groups of malate by the fumarase reaction. While C-2 position of pyruvate was only weakly respired, the species-specific difference in natural δ(13)CLEDR patterns were best reflected by the (13)CO2 respiration patterns of the C-1 position of pyruvate. Furthermore, (13)C label from malate and pyruvate were mainly allocated to amino and organic acid fractions in both species and only little to sugar and lipid fractions. In summary, our results suggest that respiration of both carboxyl groups of malate (via fumarase) by tricarboxylic acid cycle reactions or by NAD-malic enzyme influences δ(13)CLEDR. The latter supplies the pyruvate dehydrogenase reaction, which in turn determines natural δ(13)CLEDR pattern by releasing the C-1 position of pyruvate.
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Affiliation(s)
- Marco M. Lehmann
- Laboratory of Atmospheric Chemistry, Paul Scherrer InstituteVilligen, Switzerland
- Institute of Agricultural Sciences, ETH ZurichZurich, Switzerland
| | | | - Matti Barthel
- Institute of Agricultural Sciences, ETH ZurichZurich, Switzerland
| | - Veronica G. Maurino
- Plant Molecular Physiology and Biotechnology Group, Institute of Developmental and Molecular Biology of Plants, Heinrich Heine University and Cluster of Excellence on Plant Sciences (CEPLAS)Düsseldorf, Germany
| | - Rolf T. W. Siegwolf
- Laboratory of Atmospheric Chemistry, Paul Scherrer InstituteVilligen, Switzerland
| | - Nina Buchmann
- Institute of Agricultural Sciences, ETH ZurichZurich, Switzerland
| | | | - Roland A. Werner
- Institute of Agricultural Sciences, ETH ZurichZurich, Switzerland
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17
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Igamberdiev AU, Eprintsev AT. Organic Acids: The Pools of Fixed Carbon Involved in Redox Regulation and Energy Balance in Higher Plants. FRONTIERS IN PLANT SCIENCE 2016; 7:1042. [PMID: 27471516 PMCID: PMC4945632 DOI: 10.3389/fpls.2016.01042] [Citation(s) in RCA: 187] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 07/04/2016] [Indexed: 05/18/2023]
Abstract
Organic acids are synthesized in plants as a result of the incomplete oxidation of photosynthetic products and represent the stored pools of fixed carbon accumulated due to different transient times of conversion of carbon compounds in metabolic pathways. When redox level in the cell increases, e.g., in conditions of active photosynthesis, the tricarboxylic acid (TCA) cycle in mitochondria is transformed to a partial cycle supplying citrate for the synthesis of 2-oxoglutarate and glutamate (citrate valve), while malate is accumulated and participates in the redox balance in different cell compartments (via malate valve). This results in malate and citrate frequently being the most accumulated acids in plants. However, the intensity of reactions linked to the conversion of these compounds can cause preferential accumulation of other organic acids, e.g., fumarate or isocitrate, in higher concentrations than malate and citrate. The secondary reactions, associated with the central metabolic pathways, in particularly with the TCA cycle, result in accumulation of other organic acids that are derived from the intermediates of the cycle. They form the additional pools of fixed carbon and stabilize the TCA cycle. Trans-aconitate is formed from citrate or cis-aconitate, accumulation of hydroxycitrate can be linked to metabolism of 2-oxoglutarate, while 4-hydroxy-2-oxoglutarate can be formed from pyruvate and glyoxylate. Glyoxylate, a product of either glycolate oxidase or isocitrate lyase, can be converted to oxalate. Malonate is accumulated at high concentrations in legume plants. Organic acids play a role in plants in providing redox equilibrium, supporting ionic gradients on membranes, and acidification of the extracellular medium.
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Affiliation(s)
- Abir U. Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John’sNL, Canada
- *Correspondence: Abir U. Igamberdiev,
| | - Alexander T. Eprintsev
- Department of Biochemistry and Cell Physiology, Voronezh State UniversityVoronezh, Russia
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18
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Maurino VG, Engqvist MKM. 2-Hydroxy Acids in Plant Metabolism. THE ARABIDOPSIS BOOK 2015; 13:e0182. [PMID: 26380567 PMCID: PMC4568905 DOI: 10.1199/tab.0182] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Glycolate, malate, lactate, and 2-hydroxyglutarate are important 2-hydroxy acids (2HA) in plant metabolism. Most of them can be found as D- and L-stereoisomers. These 2HA play an integral role in plant primary metabolism, where they are involved in fundamental pathways such as photorespiration, tricarboxylic acid cycle, glyoxylate cycle, methylglyoxal pathway, and lysine catabolism. Recent molecular studies in Arabidopsis thaliana have helped elucidate the participation of these 2HA in in plant metabolism and physiology. In this chapter, we summarize the current knowledge about the metabolic pathways and cellular processes in which they are involved, focusing on the proteins that participate in their metabolism and cellular/intracellular transport in Arabidopsis.
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Affiliation(s)
- Veronica G. Maurino
- institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich Heine University, Universitätsstraße 1, and Cluster of Excellence on Plant Sciences (CEPLAS), 40225 Düsseldorf, Germany
| | - Martin K. M. Engqvist
- institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich Heine University, Universitätsstraße 1, and Cluster of Excellence on Plant Sciences (CEPLAS), 40225 Düsseldorf, Germany
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19
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Etienne A, Génard M, Bugaud C. A Process-Based Model of TCA Cycle Functioning to Analyze Citrate Accumulation in Pre- and Post-Harvest Fruits. PLoS One 2015; 10:e0126777. [PMID: 26042830 PMCID: PMC4456289 DOI: 10.1371/journal.pone.0126777] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 04/07/2015] [Indexed: 11/19/2022] Open
Abstract
Citrate is one of the most important organic acids in many fruits and its concentration plays a critical role in organoleptic properties. The regulation of citrate accumulation throughout fruit development, and the origins of the phenotypic variability of the citrate concentration within fruit species remain to be clarified. In the present study, we developed a process-based model of citrate accumulation based on a simplified representation of the TCA cycle to predict citrate concentration in fruit pulp during the pre- and post-harvest stages. Banana fruit was taken as a reference because it has the particularity of having post-harvest ripening, during which citrate concentration undergoes substantial changes. The model was calibrated and validated on the two stages, using data sets from three contrasting cultivars in terms of citrate accumulation, and incorporated different fruit load, potassium supply, and harvest dates. The model predicted the pre and post-harvest dynamics of citrate concentration with fairly good accuracy for the three cultivars. The model suggested major differences in TCA cycle functioning among cultivars during post-harvest ripening of banana, and pointed to a potential role for NAD-malic enzyme and mitochondrial malate carriers in the genotypic variability of citrate concentration. The sensitivity of citrate accumulation to growth parameters and temperature differed among cultivars during post-harvest ripening. Finally, the model can be used as a conceptual basis to study citrate accumulation in fleshy fruits and may be a powerful tool to improve our understanding of fruit acidity.
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Affiliation(s)
- Audrey Etienne
- UMR QUALISUD, Centre de Coopération International en Recherche Agronomique pour le Développement (CIRAD), Campus Agro-Environnemental Caraïbe, Lamentin, France
| | - Michel Génard
- UR 1115 Plantes et Systèmes de Cultures Horticoles, INRA, Avignon, France
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20
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Allen DK, Evans BS, Libourel IGL. Analysis of isotopic labeling in peptide fragments by tandem mass spectrometry. PLoS One 2014; 9:e91537. [PMID: 24626471 PMCID: PMC3953442 DOI: 10.1371/journal.pone.0091537] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 02/13/2014] [Indexed: 01/18/2023] Open
Abstract
Phenotype in multicellular organisms is the consequence of dynamic metabolic events that occur in a spatially dependent fashion. This spatial and temporal complexity presents challenges for investigating metabolism; creating a need for improved methods that effectively probe biochemical events such as amino acid biosynthesis. Isotopic labeling can provide a temporal-spatial recording of metabolic events through, for example, the description of enriched amino acids in the protein pool. Proteins are therefore an important readout of metabolism and can be assessed with modern mass spectrometers. We compared the measurement of isotopic labeling in MS2 spectra obtained from tandem mass spectrometry under either higher energy collision dissociation (HCD) or collision induced dissociation (CID) at varied energy levels. Developing soybean embryos cultured with or without 13C-labeled substrates, and Escherichia coli MG1655 enriched by feeding 7% uniformly labeled glucose served as a source of biological material for protein evaluation. CID with low energies resulted in a disproportionate amount of heavier isotopologues remaining in the precursor isotopic distribution. HCD resulted in fewer quantifiable products; however deviation from predicted distributions were small relative to the CID-based comparisons. Fragment ions have the potential to provide information on the labeling of amino acids in peptides, but our results indicate that without further development the use of this readout in quantitative methods such as metabolic flux analysis is limited.
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Affiliation(s)
- Doug K. Allen
- United States Department of Agriculture, Agricultural Research Service, Plant Genetic Research Unit, St. Louis, Missouri, United States of America
- Donald Danforth Plant Science Center, St. Louis, Missouri, United States of America
| | - Bradley S. Evans
- Donald Danforth Plant Science Center, St. Louis, Missouri, United States of America
| | - Igor G. L. Libourel
- Department of Plant Biology, University of Minnesota, St. Paul, Minnesota, United States of America
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21
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Du J, Yan C, Li Z. Phosphorus and cadmium interactions in Kandelia obovata (S. L.) in relation to cadmium tolerance. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2014; 21:355-365. [PMID: 23775005 DOI: 10.1007/s11356-013-1910-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Accepted: 06/04/2013] [Indexed: 06/02/2023]
Abstract
This study focused on the cadmium (Cd) tolerance of mangroves with application of phosphate (P) in order to explore whether exogenous P can alleviate Cd stress on these intertidal species. Kandelia obovata (S. L.) seedlings were cultivated in rhizoboxes under different levels of Cd and P concentrations. The speciation distributions of Cd in the rhizosphere and non-rhizosphere sediments were examined by sequential extraction procedures; organic acid in plant tissues and soil solution was measured by high-performance liquid chromatography; Cd and P accumulation in the plants was also determined. Results showed that considerable differences existed in Cd speciation distributions between rhizosphere and non-rhizosphere sediments. Root activity influenced the dynamics of Cd, P application increased the organic acid content in root tissues, P also increased Cd accumulation in roots whilst lowering Cd translocation from root to the above-ground tissues, and a significant positive correlation was found between Cd and P in roots (r = 0.905). It is postulated that Cd detoxification of K. obovata (S. L.) is associated with higher Cd immobilization in the presence of higher P and organic acid contents in root tissue.
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Affiliation(s)
- Jingna Du
- Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, Xiamen University, Xiamen, 361005, China
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22
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Etienne A, Génard M, Lobit P, Mbeguié-A-Mbéguié D, Bugaud C. What controls fleshy fruit acidity? A review of malate and citrate accumulation in fruit cells. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:1451-69. [PMID: 23408829 DOI: 10.1093/jxb/ert035] [Citation(s) in RCA: 260] [Impact Index Per Article: 23.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Fleshy fruit acidity is an important component of fruit organoleptic quality and is mainly due to the presence of malic and citric acids, the main organic acids found in most ripe fruits. The accumulation of these two acids in fruit cells is the result of several interlinked processes that take place in different compartments of the cell and appear to be under the control of many factors. This review combines analyses of transcriptomic, metabolomic, and proteomic data, and fruit process-based simulation models of the accumulation of citric and malic acids, to further our understanding of the physiological mechanisms likely to control the accumulation of these two acids during fruit development. The effects of agro-environmental factors, such as the source:sink ratio, water supply, mineral nutrition, and temperature, on citric and malic acid accumulation in fruit cells have been reported in several agronomic studies. This review sheds light on the interactions between these factors and the metabolism and storage of organic acids in the cell.
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Affiliation(s)
- A Etienne
- Centre de Coopération International en Recherche Agronomique pour le Développement (CIRAD), UMR QUALISUD, Pôle de Recherche Agronomique de Martinique, BP 214, 97 285 Lamentin Cedex 2, France
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23
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Allen DK, Young JD. Carbon and nitrogen provisions alter the metabolic flux in developing soybean embryos. PLANT PHYSIOLOGY 2013; 161:1458-75. [PMID: 23314943 PMCID: PMC3585609 DOI: 10.1104/pp.112.203299] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Accepted: 01/09/2013] [Indexed: 05/19/2023]
Abstract
Soybean (Glycine max) seeds store significant amounts of their biomass as protein, levels of which reflect the carbon and nitrogen received by the developing embryo. The relationship between carbon and nitrogen supply during filling and seed composition was examined through a series of embryo-culturing experiments. Three distinct ratios of carbon to nitrogen supply were further explored through metabolic flux analysis. Labeling experiments utilizing [U-(13)C5]glutamine, [U-(13)C4]asparagine, and [1,2-(13)C2]glucose were performed to assess embryo metabolism under altered feeding conditions and to create corresponding flux maps. Additionally, [U-(14)C12]sucrose, [U-(14)C6]glucose, [U-(14)C5]glutamine, and [U-(14)C4]asparagine were used to monitor differences in carbon allocation. The analyses revealed that: (1) protein concentration as a percentage of total soybean embryo biomass coincided with the carbon-to-nitrogen ratio; (2) altered nitrogen supply did not dramatically impact relative amino acid or storage protein subunit profiles; and (3) glutamine supply contributed 10% to 23% of the carbon for biomass production, including 9% to 19% of carbon to fatty acid biosynthesis and 32% to 46% of carbon to amino acids. Seed metabolism accommodated different levels of protein biosynthesis while maintaining a consistent rate of dry weight accumulation. Flux through ATP-citrate lyase, combined with malic enzyme activity, contributed significantly to acetyl-coenzyme A production. These fluxes changed with plastidic pyruvate kinase to maintain a supply of pyruvate for amino and fatty acids. The flux maps were independently validated by nitrogen balancing and highlight the robustness of primary metabolism.
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Affiliation(s)
- Doug K Allen
- United States Department of Agriculture-Agricultural Research Service, Plant Genetic Research Unit, St. Louis, MO 63132, USA.
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24
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Arias CL, Andreo CS, Drincovich MF, Gerrard Wheeler MC. Fumarate and cytosolic pH as modulators of the synthesis or consumption of C(4) organic acids through NADP-malic enzyme in Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 2013; 81:297-307. [PMID: 23242919 DOI: 10.1007/s11103-012-9999-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Accepted: 12/06/2012] [Indexed: 05/13/2023]
Abstract
Arabidopsis thaliana is a plant species that accumulates high levels of organic acids and uses them as carbon, energy and reducing power sources. Among the enzymes that metabolize these compounds, one of the most important ones is malic enzyme (ME). A. thaliana contains four malic enzymes (NADP-ME 1-4) to catalyze the reversible oxidative decarboxylation of malate in the presence of NADP. NADP-ME2 is the only one located in the cell cytosol of all Arabidopsis organs providing most of the total NADP-ME activity. In the present work, the regulation of this key enzyme by fumarate was investigated by kinetic assays, structural analysis and a site-directed mutagenesis approach. The final effect of this metabolite on NADP-ME2 forward activity not only depends on fumarate and substrate concentrations but also on the pH of the reaction medium. Fumarate produced an increase in NADP-ME2 activity by binding to an allosteric site. However at higher concentrations, fumarate caused a competitive inhibition, excluding the substrate malate from binding to the active site. The characterization of ME2-R115A mutant, which is not activated by fumarate, confirms this hypothesis. In addition, the reverse reaction (reductive carboxylation of pyruvate) is also modulated by fumarate, but in a different way. The results indicate pH-dependence of the fumarate modulation with opposite behavior on the two activities analyzed. Thereby, the coordinated action of fumarate over the direct and reverse reactions would allow a precise and specific modulation of the metabolic flux through this enzyme, leading to the synthesis or degradation of C(4) compounds under certain conditions. Thus, the physiological context might be exerting an accurate control of ME activity in planta, through changes in metabolite and substrate concentrations and cytosolic pH.
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Affiliation(s)
- Cintia Lucía Arias
- Centro de Estudios Fotosintéticos y Bioquímicos, Universidad Nacional de Rosario, Suipacha 531, Rosario, Argentina
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Tcherkez G, Mahé A, Guérard F, Boex-Fontvieille ERA, Gout E, Lamothe M, Barbour MM, Bligny R. Short-term effects of CO(2) and O(2) on citrate metabolism in illuminated leaves. PLANT, CELL & ENVIRONMENT 2012; 35:2208-2220. [PMID: 22646810 DOI: 10.1111/j.1365-3040.2012.02550.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Although there is now a considerable literature on the inhibition of leaf respiration (CO(2) evolution) by light, little is known about the effect of other environmental conditions on day respiratory metabolism. In particular, CO(2) and O(2) mole fractions are assumed to cause changes in the tricarboxylic acid pathway (TCAP) but the amplitude and even the direction of such changes are still a matter of debate. Here, we took advantage of isotopic techniques, new simple equations and instant freeze sampling to follow respiratory metabolism in illuminated cocklebur leaves (Xanthium strumarium L.) under different CO(2) /O(2) conditions. Gas exchange coupled to online isotopic analysis showed that CO(2) evolved by leaves in the light came from 'old' carbon skeletons and there was a slight decrease in (13) C natural abundance when [CO(2) ] increased. This suggested the involvement of enzymatic steps fractionating more strongly against (13) C and thus increasingly limiting for the metabolic respiratory flux as [CO(2) ] increased. Isotopic labelling with (13) C(2) -2,4-citrate lead to (13) C-enriched Glu and 2-oxoglutarate (2OG), clearly demonstrating poor metabolism of citrate by the TCAP. There was a clear relationship between the ribulose-1,5-bisphosphate oxygenation-to-carboxylation ratio (v(o) /v(c) ) and the (13) C commitment to 2OG, demonstrating that 2OG and Glu synthesis via the TCAP is positively influenced by photorespiration.
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Affiliation(s)
- Guillaume Tcherkez
- Institut de Biologie des Plantes, CNRS UMR8618, Université Paris-Sud, 91405 Orsay Cedex, France.
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Abstract
For optimal plant growth and development, cellular nitrogen (N) metabolism must be closely coordinated with other metabolic pathways, and mitochondria are thought to play a central role in this process. Recent studies using genetically modified plants have provided insight into the role of mitochondria in N metabolism. Mitochondrial metabolism is linked with N assimilation by amino acid, carbon (C) and redox metabolism. Mitochondria are not only an important source of C skeletons for N incorporation, they also produce other necessary metabolites and energy used in N remobilization processes. Nitric oxide of mitochondrial origin regulates respiration and influences primary N metabolism. Here, we discuss the changes in mitochondrial metabolism during ammonium or nitrate nutrition and under low N conditions. We also describe the involvement of mitochondria in the redistribution of N during senescence. The aim of this review was to demonstrate the role of mitochondria as an integration point of N cellular metabolism.
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Affiliation(s)
- Bożena Szal
- Institute of Experimental Plant Biology and Biotechnology, Faculty of Biology, University of Warsaw, Warsaw, Poland.
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27
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Etxeberria E, Pozueta-Romero J, Gonzalez P. In and out of the plant storage vacuole. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2012; 190:52-61. [PMID: 22608519 DOI: 10.1016/j.plantsci.2012.03.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Revised: 03/15/2012] [Accepted: 03/29/2012] [Indexed: 05/08/2023]
Abstract
The plant storage vacuole is involved in a wide variety of metabolic functions a great many of which necessitate the transport of substances across the tonoplast. Some solutes, depending on the origin, have to cross the plasma membrane as well. The cell is equipped with a complex web of transport systems, cellular routes, and unique intracellular environments that support their transport and accumulation against a concentration gradient. These are capable of processing a diverse nature of substances of distinct sizes, chemical properties, and origins. In this review we describe the various mechanism involved in solute transport into the vacuole of storage cells with special emphasis placed on solutes arriving through the apoplast. Transport of solutes from the cytosol to the vacuole is carried out by tonoplast-bound ABC transporters, solute/H(+) antiporters, and ion channels whereas transport from the apoplast requires additional plasma membrane-bound solute/H(+) symporters and fluid-phase endocytosis. In addition, and based on new evidence accumulated within the last decade, we re-evaluate the current notion of extracellular solute uptake as partially based on facilitated diffusion, and offer an alternative interpretation that involves membrane bound transporters and fluid-phase endocytosis. Finally, we make several assertions in regards to solute export from the vacuole as predicted by the limited available data suggesting that both membrane-bound carriers and vesicle mediated exocytosis are involved during solute mobilization.
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Affiliation(s)
- Ed Etxeberria
- University of Florida/IFAS, Department of Horticultural Sciences, Citrus Research and Education Center, 700 Experiment Station Road, Lake Alfred, FL 33850, USA.
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28
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Kueger S, Steinhauser D, Willmitzer L, Giavalisco P. High-resolution plant metabolomics: from mass spectral features to metabolites and from whole-cell analysis to subcellular metabolite distributions. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 70:39-50. [PMID: 22449042 DOI: 10.1111/j.1365-313x.2012.04902.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The main goal of metabolomics is the comprehensive qualitative and quantitative analysis of the time- and space-resolved distribution of all metabolites present in a given biological system. Because metabolite structures, in contrast to transcript and protein sequences, are not directly deducible from the genomic DNA sequence, the massive increase in genomic information is only indirectly of use to metabolomics, leaving compound annotation as a key problem to be solved by the available analytical techniques. Furthermore, as metabolites vary widely in both concentration and chemical behavior, there is no single analytical procedure allowing the unbiased and comprehensive structural elucidation and determination of all metabolites present in a given biological system. In this review the different approaches for targeted and non-targeted metabolomics analysis will be described with special emphasis on mass spectrometry-based techniques. Particular attention is given to approaches which can be employed for the annotation of unknown compounds. In the second part, the different experimental approaches aimed at tissue-specific or subcellular analysis of metabolites are discussed including a range of non-mass spectrometry based technologies.
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Affiliation(s)
- Stephan Kueger
- Botanical Institute II, University of Cologne, Zülpicherstrasse 47b, Cologne, Germany
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29
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Boisson AM, Gout E, Bligny R, Rivasseau C. A simple and efficient method for the long-term preservation of plant cell suspension cultures. PLANT METHODS 2012; 8:4. [PMID: 22289515 PMCID: PMC3284881 DOI: 10.1186/1746-4811-8-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2011] [Accepted: 01/30/2012] [Indexed: 05/04/2023]
Abstract
BACKGROUND The repeated weekly subculture of plant cell suspension is labour intensive and increases the risk of variation from parental cells lines. Most of the procedures to preserve cultures are based on controlled freezing/thawing and storage in liquid nitrogen. However, cells viability after unfreezing is uncertain. The long-term storage and regeneration of plant cell cultures remains a priority. RESULTS Sycamore (Acer pseudoplatanus) and Arabidopsis cell were preserved over six months as suspensions cultures in a phosphate-free nutrient medium at 5°C. The cell recovery monitored via gas exchange measurements and metabolic profiling using in vitro and in vivo 13C- and 31P-NMR took a couple of hours, and cell growth restarted without appreciable delay. No measurable cell death was observed. CONCLUSION We provide a simple method to preserve physiologically homogenous plant cell cultures without subculture over several months. The protocol based on the blockage of cell growth and low culture temperature is robust for heterotrophic and semi-autotrophic cells and should be adjustable to cell lines other than those utilised in this study. It requires no specialized equipment and is suitable for routine laboratory use.
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Affiliation(s)
- Anne-Marie Boisson
- Commissariat à l'Energie Atomique, institut de Recherche en Technologies et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Unité Mixte de Recherche 5168 CNRS, UJF, INRA, CEA, F-38054 Grenoble, France
| | - Elisabeth Gout
- Commissariat à l'Energie Atomique, institut de Recherche en Technologies et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Unité Mixte de Recherche 5168 CNRS, UJF, INRA, CEA, F-38054 Grenoble, France
| | - Richard Bligny
- Commissariat à l'Energie Atomique, institut de Recherche en Technologies et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Unité Mixte de Recherche 5168 CNRS, UJF, INRA, CEA, F-38054 Grenoble, France
| | - Corinne Rivasseau
- Commissariat à l'Energie Atomique, institut de Recherche en Technologies et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Unité Mixte de Recherche 5168 CNRS, UJF, INRA, CEA, F-38054 Grenoble, France
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30
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Walker RP, Battistelli A, Moscatello S, Chen ZH, Leegood RC, Famiani F. Phosphoenolpyruvate carboxykinase in cherry (Prunus avium L.) fruit during development. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:5357-65. [PMID: 21908472 DOI: 10.1093/jxb/err189] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In this study the abundance and location of phosphoenolpyruvate carboxykinase (PEPCK) was determined in the flesh and skin of the sweet cherry (Prunus avium L.) cultivar Durone Nero II during development. PEPCK was not present in young fruit but appeared in both tissues as the fruit increased in size. In these there was no net dissimilation of malic acid, which accounts for the bulk of their organic acid contents when PEPCK was present. To assist in understanding the function of PEPCK, the abundance of a number of other enzymes was determined. These enzymes were aspartate aminotransferase (AspAT), glutamine synthetase (GS), phosphoenolpyruvate carboxylase (PEPC), pyruvate, orthophosphate dikinase (PPDK), and ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco). A potential role for PEPCK in the regulation of pH and the utilization of malate in gluconeogenesis in the flesh and skin of cherries is presented.
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Affiliation(s)
- Robert P Walker
- Dipartimento di Scienze Agrarie e Ambientali, Università degli Studi di Perugia, Borgo XX Giugno, 74, I-06121, Perugia, Italy.
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31
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Tcherkez G, Mahé A, Boex-Fontvieille E, Gout E, Guérard F, Bligny R. Experimental evidence of phosphoenolpyruvate resynthesis from pyruvate in illuminated leaves. PLANT PHYSIOLOGY 2011; 157:86-95. [PMID: 21730197 PMCID: PMC3165900 DOI: 10.1104/pp.111.180711] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 06/30/2011] [Indexed: 05/18/2023]
Abstract
Day respiration is the cornerstone of nitrogen assimilation since it provides carbon skeletons to primary metabolism for glutamate (Glu) and glutamine synthesis. However, recent studies have suggested that the tricarboxylic acid pathway is rate limiting and mitochondrial pyruvate dehydrogenation is partly inhibited in the light. Pyruvate may serve as a carbon source for amino acid (e.g. alanine) or fatty acid synthesis, but pyruvate metabolism is not well documented, and neither is the possible resynthesis of phosphoenolpyruvate (PEP). Here, we examined the capacity of pyruvate to convert back to PEP using (13)C and (2)H labeling in illuminated cocklebur (Xanthium strumarium) leaves. We show that the intramolecular labeling pattern in Glu, 2-oxoglutarate, and malate after (13)C-3-pyruvate feeding was consistent with (13)C redistribution from PEP via the PEP-carboxylase reaction. Furthermore, the deuterium loss in Glu after (2)H(3)-(13)C-3-pyruvate feeding suggests that conversion to PEP and back to pyruvate washed out (2)H atoms to the solvent. Our results demonstrate that in cocklebur leaves, PEP resynthesis occurred as a flux from pyruvate, approximately 0.5‰ of the net CO(2) assimilation rate. This is likely to involve pyruvate inorganic phosphate dikinase and the fundamental importance of this flux for PEP and inorganic phosphate homeostasis is discussed.
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Affiliation(s)
- Guillaume Tcherkez
- Institut de Biologie des Plantes, Centre National de la Recherche Scientifique Unité Mixte de Recherche 8618, France.
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32
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Wahrheit J, Nicolae A, Heinzle E. Eukaryotic metabolism: measuring compartment fluxes. Biotechnol J 2011; 6:1071-85. [PMID: 21910257 DOI: 10.1002/biot.201100032] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 07/18/2011] [Accepted: 07/26/2011] [Indexed: 12/21/2022]
Abstract
Metabolic compartmentation represents a major characteristic of eukaryotic cells. The analysis of compartmented metabolic networks is complicated by separation and parallelization of pathways, intracellular transport, and the need for regulatory systems to mediate communication between interdependent compartments. Metabolic flux analysis (MFA) has the potential to reveal compartmented metabolic events, although it is a challenging task requiring demanding experimental techniques and sophisticated modeling. At present no ready-made solution can be provided to cope with the complexity of compartmented metabolic networks, but new powerful tools are emerging. This review gives an overview of different strategies to approach this issue, focusing on different MFA methods and highlighting the additional information that should be included to improve the outcome of an experiment and associate estimation procedures.
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Affiliation(s)
- Judith Wahrheit
- Biochemical Engineering, Saarland University, Saarbrücken, Germany
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33
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Werner RA, Buchmann N, Siegwolf RTW, Kornexl BE, Gessler A. Metabolic fluxes, carbon isotope fractionation and respiration--lessons to be learned from plant biochemistry. THE NEW PHYTOLOGIST 2011; 191:10-15. [PMID: 21521226 DOI: 10.1111/j.1469-8137.2011.03741.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Affiliation(s)
- Roland A Werner
- Institute of Agricultural Sciences, ETH Zurich, Universitaetsstrasse 2, 8092 Zurich, Switzerland
- (Author for correspondence: tel: +41 44 632 6754; email )
| | - Nina Buchmann
- Institute of Agricultural Sciences, ETH Zurich, Universitaetsstrasse 2, 8092 Zurich, Switzerland
| | - Rolf T W Siegwolf
- Lab for Atmospheric Chemistry, Stable Isotopes and Ecosystem Fluxes, Paul Scherrer Institute, 5232 Villigen PSI, Switzerland
| | - Barbara E Kornexl
- Institute of Agricultural Sciences, ETH Zurich, Universitaetsstrasse 2, 8092 Zurich, Switzerland
| | - Arthur Gessler
- Institute for Landscape Biogeochemistry, Leibniz-Centre for Agricultural Landscape Research (ZALF), Eberswalderstr. 84, 15374 Müncheberg, Germany
- Professorship for Landscape Biogeochemistry, Humboldt-University at Berlin, Lentze-Allee 75, 14195 Berlin, Germany
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34
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Araújo WL, Nunes-Nesi A, Fernie AR. Fumarate: Multiple functions of a simple metabolite. PHYTOCHEMISTRY 2011; 72:838-43. [PMID: 21440919 DOI: 10.1016/j.phytochem.2011.02.028] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Revised: 02/25/2011] [Accepted: 02/28/2011] [Indexed: 05/19/2023]
Abstract
Although much is now known about fumarate metabolism, our knowledge of some aspects of its biological function remain far from comprehensive. In this short review we begin with an introductory overview of the role of fumarate in both plant and non-plant systems. We next highlight the relative importance of fumarate in relation to cell type and circumstance in contrast to other chemically similar organic acids. Considerable cumulative evidence is suggestive of a role for fumarate in pH regulation during nitrate assimilation and that fumarate has similar effects as malate during stomatal movement. Indeed it is currently difficult to separate the biological function of fumarate from malate under certain circumstances. However, in other cases this can be easily performed. This physiological complexity notwithstanding it remains possible that the engineering of fumarate metabolism may provide opportunities to improve plant growth and performance.
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Affiliation(s)
- Wagner L Araújo
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany
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35
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Gout E, Bligny R, Douce R, Boisson AM, Rivasseau C. Early response of plant cell to carbon deprivation: in vivo 31P-NMR spectroscopy shows a quasi-instantaneous disruption on cytosolic sugars, phosphorylated intermediates of energy metabolism, phosphate partitioning, and intracellular pHs. THE NEW PHYTOLOGIST 2011; 189:135-47. [PMID: 20819175 DOI: 10.1111/j.1469-8137.2010.03449.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
• In plant cells, sugar starvation triggers a cascade of effects at the scale of 1-2 days. However, very early metabolic response has not yet been investigated. • Soluble phosphorus (P) compounds and intracellular pHs were analysed each 2.5 min intervals in heterotrophic sycamore (Acer pseudoplatanus) cells using in vivo phosphorus nuclear magnetic resonance ((31)P-NMR). • Upon external-sugar withdrawal, the glucose 6-P concentration dropped in the cytosol, but not in plastids. The released inorganic phosphate (Pi) accumulated transiently in the cytosol before influx into the vacuole; nucleotide triphosphate concentration doubled, intracellular pH increased and cell respiration decreased. It was deduced that the cytosolic free-sugar concentration was low, corresponding to only 0.5 mM sucrose in sugar-supplied cells. • The release of sugar from the vacuole and from plastids is insufficient to fully sustain the cell metabolism during starvation, particularly in the very short term. Similarly to Pi-starvation, the cell's first response to sugar starvation occurs in the cytosol and is of a metabolic nature. Unlike the cytoplasm, cytosolic homeostasis is not maintained during starvation. The important metabolic changes following cytosolic sugar exhaustion deliver early endogenous signals that may contribute to trigger rescue metabolism.
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Affiliation(s)
- Elisabeth Gout
- Commissariat à l'Energie Atomique, institut de Recherche en Technologies et Sciences pour le Vivant, Unité Mixte de Recherche 5168 CNRS, UJF, INRA, CEA, Grenoble, France
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36
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Sweetlove LJ, Beard KFM, Nunes-Nesi A, Fernie AR, Ratcliffe RG. Not just a circle: flux modes in the plant TCA cycle. TRENDS IN PLANT SCIENCE 2010; 15:462-70. [PMID: 20554469 DOI: 10.1016/j.tplants.2010.05.006] [Citation(s) in RCA: 497] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 05/09/2010] [Accepted: 05/17/2010] [Indexed: 05/20/2023]
Abstract
The tricarboxylic acid (TCA) cycle is one of the iconic pathways in metabolism. The cycle is commonly thought of in terms of energy metabolism, being responsible for the oxidation of respiratory substrates to drive ATP synthesis. However, the reactions of carboxylic acid metabolism are embedded in a larger metabolic network and the conventional TCA cycle is only one way in which the component reactions can be organised. Recent evidence from labelling studies and metabolic network models suggest that the organisation of carboxylic acid metabolism in plants is highly dependent on the metabolic and physiological demands of the cell. Thus, alternative, non-cyclic flux modes occur in leaves in the light, in some developing oilseeds, and under specific physiological circumstances such as anoxia.
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Affiliation(s)
- Lee J Sweetlove
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX13RB, UK.
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37
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Pracharoenwattana I, Zhou W, Keech O, Francisco PB, Udomchalothorn T, Tschoep H, Stitt M, Gibon Y, Smith SM. Arabidopsis has a cytosolic fumarase required for the massive allocation of photosynthate into fumaric acid and for rapid plant growth on high nitrogen. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 62:785-95. [PMID: 20202172 DOI: 10.1111/j.1365-313x.2010.04189.x] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The Arabidopsis genome has two fumarase genes, one of which encodes a protein with mitochondrial targeting information (FUM1) while the other (FUM2) does not. We show that a FUM1-green fluorescent protein fusion is directed to mitochondria while FUM2-red fluorescent protein remains in the cytosol. While mitochondrial FUM1 is an essential gene, cytosolic FUM2 is not required for plant growth. However FUM2 is required for the massive accumulation of carbon into fumarate that occurs in Arabidopsis leaves during the day. In fum2 knock-out mutants, fumarate levels remain low while malate increases, and these changes can be reversed with a FUM2 transgene. The fum2 mutant has lower levels of many amino acids in leaves during the day compared with the wild type, but higher levels at night, consistent with a link between fumarate and amino acid metabolism. To further test this relationship we grew plants in the absence or presence of nitrogen fertilizer. The amount of fumarate in leaves increased several fold in response to nitrogen in wild-type plants, but not in fum2. Malate increased to a small extent in the wild type but to a greater extent in fum2. Growth of fum2 plants was similar to that of the wild type in low nitrogen but much slower in the presence of high nitrogen. Activities of key enzymes of nitrogen assimilation were similar in both genotypes. We conclude that FUM2 is required for the accumulation of fumarate in leaves, which is in turn required for rapid nitrogen assimilation and growth on high nitrogen.
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Affiliation(s)
- Itsara Pracharoenwattana
- Centres of Excellence for Plant Metabolomics and Plant Energy Biology, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
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38
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Gauthier PPG, Bligny R, Gout E, Mahé A, Nogués S, Hodges M, Tcherkez GGB. In folio isotopic tracing demonstrates that nitrogen assimilation into glutamate is mostly independent from current CO2 assimilation in illuminated leaves of Brassica napus. THE NEW PHYTOLOGIST 2010; 185:988-99. [PMID: 20070539 DOI: 10.1111/j.1469-8137.2009.03130.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
*Nitrogen assimilation in leaves requires primary NH(2) acceptors that, in turn, originate from primary carbon metabolism. Respiratory metabolism is believed to provide such acceptors (such as 2-oxoglutarate), so that day respiration is commonly seen as a cornerstone for nitrogen assimilation into glutamate in illuminated leaves. However, both glycolysis and day respiratory CO(2) evolution are known to be inhibited by light, thereby compromising the input of recent photosynthetic carbon for glutamate production. *In this study, we carried out isotopic labelling experiments with (13)CO(2) and (15)N-ammonium nitrate on detached leaves of rapeseed (Brassica napus), and performed (13)C- and (15)N-nuclear magnetic resonance analyses. *Our results indicated that the production of (13)C-glutamate and (13)C-glutamine under a (13)CO(2) atmosphere was very weak, whereas (13)C-glutamate and (13)C-glutamine appeared in both the subsequent dark period and the next light period under a (12)CO(2) atmosphere. Consistently, the analysis of heteronuclear ((13)C-(15)N) interactions within molecules indicated that most (15)N-glutamate and (15)N-glutamine molecules were not (13)C labelled after (13)C/(15)N double labelling. That is, recent carbon atoms (i.e. (13)C) were hardly incorporated into glutamate, but new glutamate molecules were synthesized, as evidenced by (15)N incorporation. *We conclude that the remobilization of night-stored molecules plays a significant role in providing 2-oxoglutarate for glutamate synthesis in illuminated rapeseed leaves, and therefore the natural day : night cycle seems critical for nitrogen assimilation.
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Affiliation(s)
- Paul P G Gauthier
- Institut de Biotechnologie des Plantes, Bâtiment 630, Université Paris-Sud XI, Orsay, France.
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39
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Zell MB, Fahnenstich H, Maier A, Saigo M, Voznesenskaya EV, Edwards GE, Andreo C, Schleifenbaum F, Zell C, Drincovich MF, Maurino VG. Analysis of Arabidopsis with highly reduced levels of malate and fumarate sheds light on the role of these organic acids as storage carbon molecules. PLANT PHYSIOLOGY 2010; 152:1251-62. [PMID: 20107023 PMCID: PMC2832245 DOI: 10.1104/pp.109.151795] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 01/23/2010] [Indexed: 05/18/2023]
Abstract
While malate and fumarate participate in a multiplicity of pathways in plant metabolism, the function of these organic acids as carbon stores in C(3) plants has not been deeply addressed. Here, Arabidopsis (Arabidopsis thaliana) plants overexpressing a maize (Zea mays) plastidic NADP-malic enzyme (MEm plants) were used to analyze the consequences of sustained low malate and fumarate levels on the physiology of this C(3) plant. When grown in short days (sd), MEm plants developed a pale-green phenotype with decreased biomass and increased specific leaf area, with thin leaves having lower photosynthetic performance. These features were absent in plants growing in long days. The analysis of metabolite levels of rosettes from transgenic plants indicated similar disturbances in both sd and long days, with very low levels of malate and fumarate. Determinations of the respiratory quotient by the end of the night indicated a shift from carbohydrates to organic acids as the main substrates for respiration in the wild type, while MEm plants use more reduced compounds, like fatty acids and proteins, to fuel respiration. It is concluded that the alterations observed in sd MEm plants are a consequence of impairment in the supply of carbon skeletons during a long dark period. This carbon starvation phenotype observed at the end of the night demonstrates a physiological role of the C(4) acids, which may be a constitutive function in plants.
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Allen DK, Libourel IGL, Shachar-Hill Y. Metabolic flux analysis in plants: coping with complexity. PLANT, CELL & ENVIRONMENT 2009; 32:1241-57. [PMID: 19422611 DOI: 10.1111/j.1365-3040.2009.01992.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Theory and experience in metabolic engineering both show that metabolism operates at the network level. In plants, this complexity is compounded by a high degree of compartmentation and the synthesis of a very wide array of secondary metabolic products. A further challenge to understanding and predicting plant metabolic function is posed by our ignorance about the structure of metabolic networks even in well-studied systems. Metabolic flux analysis (MFA) provides tools to measure and model the functioning of metabolism, and is making significant contributions to coping with their complexity. This review gives an overview of different MFA approaches, the measurements required to implement them and the information they yield. The application of MFA methods to plant systems is then illustrated by several examples from the recent literature. Next, the challenges that plant metabolism poses for MFA are discussed together with ways that these can be addressed. Lastly, new developments in MFA are described that can be expected to improve the range and reliability of plant MFA in the coming years.
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Affiliation(s)
- Doug K Allen
- Michigan State University, Plant Biology Department, East Lansing, MI 48824, USA.
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Using small molecules to facilitate exchange of bicarbonate and chloride anions across liposomal membranes. Nat Chem 2009; 1:138-44. [DOI: 10.1038/nchem.178] [Citation(s) in RCA: 175] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Accepted: 03/11/2009] [Indexed: 11/09/2022]
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Bathellier C, Tcherkez G, Bligny R, Gout E, Cornic G, Ghashghaie J. Metabolic origin of the delta13C of respired CO2 in roots of Phaseolus vulgaris. THE NEW PHYTOLOGIST 2009; 181:387-399. [PMID: 19021866 DOI: 10.1111/j.1469-8137.2008.02679.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Root respiration is a major contributor to soil CO2 efflux, and thus an important component of ecosystem respiration. But its metabolic origin, in relation to the carbon isotope composition (delta13C), remains poorly understood. Here, 13C analysis was conducted on CO2 and metabolites under typical conditions or under continuous darkness in French bean (Phaseolus vulgaris) roots. 13C contents were measured either under natural abundance or following pulse-chase labeling with 13C-enriched glucose or pyruvate, using isotope ratio mass spectrometer (IRMS) and nuclear magnetic resonance (NMR) techniques. In contrast to leaves, no relationship was found between the respiratory quotient and the delta13C of respired CO2, which stayed constant at a low value (c. -27.5 per thousand) under continuous darkness. With labeling experiments, it is shown that such a pattern is explained by the 13C-depleting effect of the pentose phosphate pathway; and the involvement of the Krebs cycle fueled by either the glycolytic input or the lipid/protein recycling. The anaplerotic phosphoenolpyruvate carboxylase (PEPc) activity sustained glutamic acid (Glu) synthesis, with no net effect on respired CO2. These results indicate that the root delta13C signal does not depend on the availability of root respiratory substrates and it is thus plausible that, unless the 13C photosynthetic fractionation varies at the leaf level, the root delta13C signal hardly changes under a range of natural environmental conditions.
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Affiliation(s)
- Camille Bathellier
- Laboratoire d'Ecologie, Systématique et Evolution (ESE), CNRS-UMR 8079 - IFR 87, Bâtiment 362, Université Paris-Sud, 91405-Orsay Cedex, France;Plateforme Métabolisme-Métabolome, IFR87 La Plante et son Environnement, Institut de Biotechnologie des Plantes, Bâtiment 630, Université Paris-Sud, 91405-Orsay Cedex, France;Laboratoire de Physiologie Cellulaire Végétale CEA-Grenoble 17, rue des Martyrs, 38054 Grenoble Cedex 9, France
| | - Guillaume Tcherkez
- Laboratoire d'Ecologie, Systématique et Evolution (ESE), CNRS-UMR 8079 - IFR 87, Bâtiment 362, Université Paris-Sud, 91405-Orsay Cedex, France;Plateforme Métabolisme-Métabolome, IFR87 La Plante et son Environnement, Institut de Biotechnologie des Plantes, Bâtiment 630, Université Paris-Sud, 91405-Orsay Cedex, France;Laboratoire de Physiologie Cellulaire Végétale CEA-Grenoble 17, rue des Martyrs, 38054 Grenoble Cedex 9, France
| | - Richard Bligny
- Laboratoire d'Ecologie, Systématique et Evolution (ESE), CNRS-UMR 8079 - IFR 87, Bâtiment 362, Université Paris-Sud, 91405-Orsay Cedex, France;Plateforme Métabolisme-Métabolome, IFR87 La Plante et son Environnement, Institut de Biotechnologie des Plantes, Bâtiment 630, Université Paris-Sud, 91405-Orsay Cedex, France;Laboratoire de Physiologie Cellulaire Végétale CEA-Grenoble 17, rue des Martyrs, 38054 Grenoble Cedex 9, France
| | - Elizabeth Gout
- Laboratoire d'Ecologie, Systématique et Evolution (ESE), CNRS-UMR 8079 - IFR 87, Bâtiment 362, Université Paris-Sud, 91405-Orsay Cedex, France;Plateforme Métabolisme-Métabolome, IFR87 La Plante et son Environnement, Institut de Biotechnologie des Plantes, Bâtiment 630, Université Paris-Sud, 91405-Orsay Cedex, France;Laboratoire de Physiologie Cellulaire Végétale CEA-Grenoble 17, rue des Martyrs, 38054 Grenoble Cedex 9, France
| | - Gabriel Cornic
- Laboratoire d'Ecologie, Systématique et Evolution (ESE), CNRS-UMR 8079 - IFR 87, Bâtiment 362, Université Paris-Sud, 91405-Orsay Cedex, France;Plateforme Métabolisme-Métabolome, IFR87 La Plante et son Environnement, Institut de Biotechnologie des Plantes, Bâtiment 630, Université Paris-Sud, 91405-Orsay Cedex, France;Laboratoire de Physiologie Cellulaire Végétale CEA-Grenoble 17, rue des Martyrs, 38054 Grenoble Cedex 9, France
| | - Jaleh Ghashghaie
- Laboratoire d'Ecologie, Systématique et Evolution (ESE), CNRS-UMR 8079 - IFR 87, Bâtiment 362, Université Paris-Sud, 91405-Orsay Cedex, France;Plateforme Métabolisme-Métabolome, IFR87 La Plante et son Environnement, Institut de Biotechnologie des Plantes, Bâtiment 630, Université Paris-Sud, 91405-Orsay Cedex, France;Laboratoire de Physiologie Cellulaire Végétale CEA-Grenoble 17, rue des Martyrs, 38054 Grenoble Cedex 9, France
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Endler A, Reiland S, Gerrits B, Schmidt UG, Baginsky S, Martinoia E. In vivo phosphorylation sites of barley tonoplast proteins identified by a phosphoproteomic approach. Proteomics 2009; 9:310-21. [DOI: 10.1002/pmic.200800323] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Tronconi MA, Fahnenstich H, Gerrard Weehler MC, Andreo CS, Flügge UI, Drincovich MF, Maurino VG. Arabidopsis NAD-malic enzyme functions as a homodimer and heterodimer and has a major impact on nocturnal metabolism. PLANT PHYSIOLOGY 2008; 146:1540-52. [PMID: 18223148 PMCID: PMC2287332 DOI: 10.1104/pp.107.114975] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Accepted: 01/23/2008] [Indexed: 05/18/2023]
Abstract
Although the nonphotosynthetic NAD-malic enzyme (NAD-ME) was assumed to play a central role in the metabolite flux through the tricarboxylic acid cycle, the knowledge on this enzyme is still limited. Here, we report on the identification and characterization of two genes encoding mitochondrial NAD-MEs from Arabidopsis (Arabidopsis thaliana), AtNAD-ME1 and AtNAD-ME2. The encoded proteins can be grouped into the two clades found in the plant NAD-ME phylogenetic tree. AtNAD-ME1 belongs to the clade that includes known alpha-subunits with molecular masses of approximately 65 kD, while AtNAD-ME2 clusters with the known beta-subunits with molecular masses of approximately 58 kD. The separated recombinant proteins showed NAD-ME activity, presented comparable kinetic properties, and are dimers in their active conformation. Native electrophoresis coupled to denaturing electrophoresis revealed that in vivo AtNAD-ME forms a dimer of nonidentical subunits in Arabidopsis. Further support for this conclusion was obtained by reconstitution of the active heterodimer in vitro. The characterization of loss-of-function mutants for both AtNAD-MEs indicated that both proteins also exhibit enzymatic activity in vivo. Neither the single nor the double mutants showed a growth or developmental phenotype, suggesting that NAD-ME activity is not essential for normal autotrophic development. Nevertheless, metabolic profiling of plants completely lacking NAD-ME activity revealed differential patterns of modifications in light and dark periods and indicates a major role for NAD-MEs during nocturnal metabolism.
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Affiliation(s)
- Marcos A Tronconi
- Centro de Estudios Fotosintéticos y Bioquímicos, Universidad Nacional de Rosario, 2000 Rosario, Argentina
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Tcherkez G, Bligny R, Gout E, Mahé A, Hodges M, Cornic G. Respiratory metabolism of illuminated leaves depends on CO2 and O2 conditions. Proc Natl Acad Sci U S A 2008; 105:797-802. [PMID: 18184808 PMCID: PMC2206616 DOI: 10.1073/pnas.0708947105] [Citation(s) in RCA: 156] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2007] [Indexed: 11/18/2022] Open
Abstract
Day respiration is the process by which nonphotorespiratory CO2 is produced by illuminated leaves. The biological function of day respiratory metabolism is a major conundrum of plant photosynthesis research: because the rate of CO2 evolution is partly inhibited in the light, it is viewed as either detrimental to plant carbon balance or necessary for photosynthesis operation (e.g., in providing cytoplasmic ATP for sucrose synthesis). Systematic variations in the rate of day respiration under contrasting environmental conditions have been used to elucidate the metabolic rationale of respiration in the light. Using isotopic techniques, we show that both glycolysis and the tricarboxylic acid cycle activities are inversely related to the ambient CO2/O2 ratio: day respiratory metabolism is enhanced under high photorespiratory (low CO2) conditions. Such a relationship also correlates with the dihydroxyacetone phosphate/Glc-6-P ratio, suggesting that photosynthetic products exert a control on day respiration. Thus, day respiration is normally inhibited by phosphoryl (ATP/ADP) and reductive (NADH/NAD) poise but is up-regulated by photorespiration. Such an effect may be related to the need for NH2 transfers during the recovery of photorespiratory cycle intermediates.
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Affiliation(s)
- Guillaume Tcherkez
- Plateforme Métabolisme-Métabolome, Institut Fédératif de Recherche 87, Bâtiment 630, 91405 Orsay Cedex, France.
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Abstract
Research into plant metabolism has a long history, and analytical approaches of ever-increasing breadth and sophistication have been brought to bear. We now have access to vast repositories of data concerning enzymology and regulatory features of enzymes, as well as large-scale datasets containing profiling information of transcripts, protein and metabolite levels. Nevertheless, despite this wealth of data, we remain some way off from being able to rationally engineer plant metabolism or even to predict metabolic responses. Within the past 18 months, rapid progress has been made, with several highly informative plant network interrogations being discussed in the literature. In the present review we will appraise the current state of the art regarding plant metabolic network analysis and attempt to outline what the necessary steps are in order to further our understanding of network regulation.
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Kovermann P, Meyer S, Hörtensteiner S, Picco C, Scholz-Starke J, Ravera S, Lee Y, Martinoia E. The Arabidopsis vacuolar malate channel is a member of the ALMT family. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 52:1169-80. [PMID: 18005230 DOI: 10.1111/j.1365-313x.2007.03367.x] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In plants, malate is a central metabolite and fulfills a large number of functions. Vacuolar malate may reach very high concentrations and fluctuate rapidly, whereas cytosolic malate is kept at a constant level allowing optimal metabolism. Recently, a vacuolar malate transporter (Arabidopsis thaliana tonoplast dicarboxylate transporter, AttDT) was identified that did not correspond to the well-characterized vacuolar malate channel. We therefore hypothesized that a member of the aluminum-activated malate transporter (ALMT) gene family could code for a vacuolar malate channel. Using GFP fusion constructs, we could show that AtALMT9 (A. thaliana ALMT9) is targeted to the vacuole. Promoter-GUS fusion constructs demonstrated that this gene is expressed in all organs, but is cell-type specific as GUS activity in leaves was detected nearly exclusively in mesophyll cells. Patch-clamp analysis of an Atalmt9 T-DNA insertion mutant exhibited strongly reduced vacuolar malate channel activity. In order to functionally characterize AtALMT9 as a malate channel, we heterologously expressed this gene in tobacco and in oocytes. Overexpression of AtALMT9-GFP in Nicotiana benthamiana leaves strongly enhanced the malate current densities across the mesophyll tonoplasts. Functional expression of AtALMT9 in Xenopus oocytes induced anion currents, which were clearly distinguishable from endogenous oocyte currents. Our results demonstrate that AtALMT9 is a vacuolar malate channel. Deletion mutants for AtALMT9 exhibit only slightly reduced malate content in mesophyll protoplasts and no visible phenotype, indicating that AttDT and the residual malate channel activity are sufficient to sustain the transport activity necessary to regulate the cytosolic malate homeostasis.
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Affiliation(s)
- Peter Kovermann
- Institute for Plant Biology, University of Zürich, CH-8008 Zürich, Switzerland
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Fahnenstich H, Saigo M, Niessen M, Zanor MI, Andreo CS, Fernie AR, Drincovich MF, Flügge UI, Maurino VG. Alteration of organic acid metabolism in Arabidopsis overexpressing the maize C4 NADP-malic enzyme causes accelerated senescence during extended darkness. PLANT PHYSIOLOGY 2007; 145:640-52. [PMID: 17885087 PMCID: PMC2048770 DOI: 10.1104/pp.107.104455] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2007] [Accepted: 09/14/2007] [Indexed: 05/17/2023]
Abstract
The full-length cDNA encoding the maize (Zea mays) C(4) NADP-malic enzyme was expressed in Arabidopsis (Arabidopsis thaliana) under the control of the cauliflower mosaic virus 35S promoter. Homozygous transgenic plants (MEm) were isolated with activities ranging from 6- to 33-fold of those found in the wild type. The transformants did not show any differences in morphology and development when grown in long days; however, dark-induced senescence progressed more rapidly in MEm plants compared to the wild type. Interestingly, senescence could be retarded in the transgenic lines by exogenously supplying glucose, sucrose, or malate, suggesting that the lack of a readily mobilized carbon source is likely to be the initial factor leading to the premature induction of senescence in MEm plants. A comprehensive metabolic profiling on whole rosettes allowed determination of approximately 80 metabolites during a diurnal cycle as well as following dark-induced senescence and during metabolic complementation assays. MEm plants showed no differences in the accumulation and degradation of carbohydrates with respect to the wild type in all conditions tested, but accumulated lower levels of intermediates used as respiratory substrates, prominently malate and fumarate. The data indicated that extremely low levels of malate and fumarate are responsible for the accelerated dark-induced senescence encountered in MEm plants. Thus, in prolonged darkness these metabolites are consumed faster than in the wild type and, as a consequence, MEm plants enter irreversible senescence more rapidly. In addition, the data revealed that both malate and fumarate are important forms of fixed carbon that can be rapidly metabolized under stress conditions in Arabidopsis.
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Baxter CJ, Liu JL, Fernie AR, Sweetlove LJ. Determination of metabolic fluxes in a non-steady-state system. PHYTOCHEMISTRY 2007; 68:2313-9. [PMID: 17582446 DOI: 10.1016/j.phytochem.2007.04.026] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Revised: 04/19/2007] [Accepted: 04/23/2007] [Indexed: 05/15/2023]
Abstract
Estimation of fluxes through metabolic networks from redistribution patterns of (13)C has become a well developed technique in recent years. However, the approach is currently limited to systems at metabolic steady-state; dynamic changes in metabolic fluxes cannot be assessed. This is a major impediment to understanding the behaviour of metabolic networks, because steady-state is not always experimentally achievable and a great deal of information about the control hierarchy of the network can be derived from the analysis of flux dynamics. To address this issue, we have developed a method for estimating non-steady-state fluxes based on the mass-balance of mass isotopomers. This approach allows multiple mass-balance equations to be written for the change in labelling of a given metabolite pool and thereby permits over-determination of fluxes. We demonstrate how linear regression methods can be used to estimate non-steady-state fluxes from these mass balance equations. The approach can be used to calculate fluxes from both mass isotopomer and positional isotopomer labelling information and thus has general applicability to data generated from common spectrometry- or NMR-based analytical platforms. The approach is applied to a GC-MS time-series dataset of (13)C-labelling of metabolites in a heterotrophic Arabidopsis cell suspension culture. Threonine biosynthesis is used to demonstrate that non-steady-state fluxes can be successfully estimated from such data while organic acid metabolism is used to highlight some common issues that can complicate flux estimation. These include multiple pools of the same metabolite that label at different rates and carbon skeleton rearrangements.
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Affiliation(s)
- C J Baxter
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
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50
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Nunes-Nesi A, Carrari F, Gibon Y, Sulpice R, Lytovchenko A, Fisahn J, Graham J, Ratcliffe RG, Sweetlove LJ, Fernie AR. Deficiency of mitochondrial fumarase activity in tomato plants impairs photosynthesis via an effect on stomatal function. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 50:1093-106. [PMID: 17461782 DOI: 10.1111/j.1365-313x.2007.03115.x] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Transgenic tomato (Solanum lycopersicum) plants expressing a fragment of a fumarate hydratase (fumarase) gene in the antisense orientation and exhibiting considerable reductions in the mitochondrial activity of this enzyme show impaired photosynthesis. The rate of the tricarboxylic acid cycle was reduced in the transformants relative to the other major pathways of carbohydrate oxidation and the plants were characterized by a restricted rate of dark respiration. However, biochemical analyses revealed relatively little alteration in leaf metabolism as a consequence of reducing the fumarase activity. That said, in comparison to wild-type plants, CO(2) assimilation was reduced by up to 50% under atmospheric conditions and plants were characterized by a reduced biomass on a whole plant basis. Analysis of further photosynthetic parameters revealed that there was little difference in pigment content in the transformants but that the rate of transpiration and stomatal conductance was markedly reduced. Analysis of the response of the rate of photosynthesis to variation in the concentration of CO(2) confirmed that this restriction was due to a deficiency in stomatal function.
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Affiliation(s)
- Adriano Nunes-Nesi
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Golm, Germany
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