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Pyrophosphate as an alternative energy currency in plants. Biochem J 2021; 478:1515-1524. [PMID: 33881486 DOI: 10.1042/bcj20200940] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 03/20/2021] [Accepted: 03/23/2021] [Indexed: 02/07/2023]
Abstract
In the conditions of [Mg2+] elevation that occur, in particular, under low oxygen stress and are the consequence of the decrease in [ATP] and increase in [ADP] and [AMP], pyrophosphate (PPi) can function as an alternative energy currency in plant cells. In addition to its production by various metabolic pathways, PPi can be synthesized in the combined reactions of pyruvate, phosphate dikinase (PPDK) and pyruvate kinase (PK) by so-called PK/PPDK substrate cycle, and in the reverse reaction of membrane-bound H+-pyrophosphatase, which uses the energy of electrochemical gradients generated on tonoplast and plasma membrane. The PPi can then be consumed in its active forms of MgPPi and Mg2PPi by PPi-utilizing enzymes, which require an elevated [Mg2+]. This ensures a continuous operation of glycolysis in the conditions of suppressed ATP synthesis, keeping metabolism energy efficient and less dependent on ATP.
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Chaudhry AH, Nayab S, Hussain SB, Ali M, Pan Z. Current Understandings on Magnesium Deficiency and Future Outlooks for Sustainable Agriculture. Int J Mol Sci 2021; 22:1819. [PMID: 33673043 PMCID: PMC7917752 DOI: 10.3390/ijms22041819] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 01/27/2021] [Accepted: 01/28/2021] [Indexed: 11/24/2022] Open
Abstract
The productivity of agricultural produce is fairly dependent on the availability of nutrients and efficient use. Magnesium (Mg2+) is an essential macronutrient of living cells and is the second most prevalent free divalent cation in plants. Mg2+ plays a role in several physiological processes that support plant growth and development. However, it has been largely forgotten in fertilization management strategies to increase crop production, which leads to severe reductions in plant growth and yield. In this review, we discuss how the Mg2+ shortage induces several responses in plants at different levels: morphological, physiological, biochemical and molecular. Additionally, the Mg2+ uptake and transport mechanisms in different cellular organelles and the role of Mg2+ transporters in regulating Mg2+ homeostasis are also discussed. Overall, in this review, we critically summarize the available information about the responses of Mg deficiency on plant growth and development, which would facilitate plant scientists to create Mg2+-deficiency-resilient crops through agronomic and genetic biofortification.
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Affiliation(s)
- Ahmad Hassan Chaudhry
- College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China;
| | - Shafa Nayab
- Department of Horticulture, Muhammad Nawaz Shareef University of Agriculture, Multan 60000, Pakistan; (S.N.); (S.B.H.)
| | - Syed Bilal Hussain
- Department of Horticulture, Muhammad Nawaz Shareef University of Agriculture, Multan 60000, Pakistan; (S.N.); (S.B.H.)
| | - Muqarrab Ali
- Department of Agronomy, Muhammad Nawaz Shareef University of Agriculture, Multan 60000, Pakistan;
| | - Zhiyong Pan
- College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China;
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Kleczkowski LA, Igamberdiev AU. Magnesium Signaling in Plants. Int J Mol Sci 2021; 22:1159. [PMID: 33503839 PMCID: PMC7865908 DOI: 10.3390/ijms22031159] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Revised: 01/16/2021] [Accepted: 01/19/2021] [Indexed: 01/02/2023] Open
Abstract
Free magnesium (Mg2+) is a signal of the adenylate (ATP+ADP+AMP) status in the cells. It results from the equilibrium of adenylate kinase (AK), which uses Mg-chelated and Mg-free adenylates as substrates in both directions of its reaction. The AK-mediated primary control of intracellular [Mg2+] is finely interwoven with the operation of membrane-bound adenylate- and Mg2+-translocators, which in a given compartment control the supply of free adenylates and Mg2+ for the AK-mediated equilibration. As a result, [Mg2+] itself varies both between and within the compartments, depending on their energetic status and environmental clues. Other key nucleotide-utilizing/producing enzymes (e.g., nucleoside diphosphate kinase) may also be involved in fine-tuning of the intracellular [Mg2+]. Changes in [Mg2+] regulate activities of myriads of Mg-utilizing/requiring enzymes, affecting metabolism under both normal and stress conditions, and impacting photosynthetic performance, respiration, phloem loading and other processes. In compartments controlled by AK equilibrium (cytosol, chloroplasts, mitochondria, nucleus), the intracellular [Mg2+] can be calculated from total adenylate contents, based on the dependence of the apparent equilibrium constant of AK on [Mg2+]. Magnesium signaling, reflecting cellular adenylate status, is likely widespread in all eukaryotic and prokaryotic organisms, due simply to the omnipresent nature of AK and to its involvement in adenylate equilibration.
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Affiliation(s)
- Leszek A. Kleczkowski
- Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, 901 87 Umeå, Sweden
| | - Abir U. Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL A1B3X9, Canada;
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Rogiers SY, Greer DH, Moroni FJ, Baby T. Potassium and Magnesium Mediate the Light and CO 2 Photosynthetic Responses of Grapevines. BIOLOGY 2020; 9:biology9070144. [PMID: 32605293 PMCID: PMC7407654 DOI: 10.3390/biology9070144] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 06/22/2020] [Accepted: 06/26/2020] [Indexed: 01/01/2023]
Abstract
Potassium (K) and magnesium (Mg) deficiency are common stresses that can impact on grape yield and quality, but their effects on photosynthesis have received little attention. Understanding the diffusional and biochemical limitations to photosynthetic constraints will help to guide improvements in cultural practices. Accordingly, the photosynthetic response of Vitis vinifera cvs. Shiraz and Chardonnay to K or Mg deficiency was assessed under hydroponic conditions using miniature low-nutrient-reserve vines. Photosynthesis was at least partly reduced by a decline in stomatal conductance. Light and CO2-saturated photosynthesis, maximum rate of ribulose 1.5 bisphospate (RuBP) carboxylation (Vcmax) and maximum rate of electron transport (Jmax) all decreased under K and Mg deficiency. Likewise, chlorophyll fluorescence and electron transport were lower under both nutrient deficiencies while dark respiration increased. K deficiency drastically reduced shoot biomass in both cultivars, while root biomass was greatly reduced under both Mg and K deficiency. Taken together, these results indicate that the decrease in biomass was likely due to both stomatal and biochemical limitations in photosynthesis. Optimising photosynthesis through adequate nutrition will thus support increases in biomass with carry-on positive effects on crop yields.
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Affiliation(s)
- Suzy Y. Rogiers
- NSW Department of Primary Industries, Wagga Wagga, NSW 2678, Australia
- National Wine and Grape Industry Centre, Charles Sturt University, Wagga Wagga, NSW 2678, Australia; (D.H.G.); (F.J.M.); (T.B.)
- Correspondence:
| | - Dennis H. Greer
- National Wine and Grape Industry Centre, Charles Sturt University, Wagga Wagga, NSW 2678, Australia; (D.H.G.); (F.J.M.); (T.B.)
| | - Francesca J. Moroni
- National Wine and Grape Industry Centre, Charles Sturt University, Wagga Wagga, NSW 2678, Australia; (D.H.G.); (F.J.M.); (T.B.)
| | - Tintu Baby
- National Wine and Grape Industry Centre, Charles Sturt University, Wagga Wagga, NSW 2678, Australia; (D.H.G.); (F.J.M.); (T.B.)
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Niu Y, Jin G, Li X, Tang C, Zhang Y, Liang Y, Yu J. Phosphorus and magnesium interactively modulate the elongation and directional growth of primary roots in Arabidopsis thaliana (L.) Heynh. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:3841-54. [PMID: 25922494 PMCID: PMC4473981 DOI: 10.1093/jxb/erv181] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A balanced supply of essential nutrients is an important factor influencing root architecture in many plants, yet data related to the interactive effects of two nutrients on root growth are limited. Here, we investigated the interactive effect between phosphorus (P) and magnesium (Mg) on root growth of Arabidopsis grown in pH-buffered agar medium at different P and Mg levels. The results showed that elongation and deviation of primary roots were directly correlated with the amount of P added to the medium but could be modified by the Mg level, which was related to the root meristem activity and stem-cell division. High P enhanced while low P decreased the tip-focused fluorescence signal of auxin biosynthesis, transport, and redistribution during elongation of primary roots; these effects were greater under low Mg than under high Mg. The altered root growth in response to P and Mg supply was correlated with AUX1, PIN2, and PIN3 mRNA abundance and expression and the accumulation of the protein. Application of either auxin influx inhibitor or efflux inhibitor inhibited the elongation and increased the deviation angle of primary roots, and decreased auxin level in root tips. Furthermore, the auxin-transport mutants aux1-22 and eir1-1 displayed reduced root growth and increased the deviation angle. Our data suggest a profound effect of the combined supply of P and Mg on the development of root morphology in Arabidopsis through auxin signals that modulate the elongation and directional growth of primary root and the expression of root differentiation and development genes.
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Affiliation(s)
- Yaofang Niu
- Department of Horticulture, College of Agricultural and Biotechnology, Zhejiang University, Hangzhou 310058, PR China College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, PR China
| | - Gulei Jin
- College of Agricultural and Biotechnology, Zhejiang University, Hangzhou 310058, PR China
| | - Xin Li
- Tea Research Institute, Chinese Academy of Agricultural Science, Hangzhou, 310008, PR China
| | - Caixian Tang
- Centre for AgriBioscience, La Trobe University, Melbourne Campus, Victoria 3086, Australia
| | - Yongsong Zhang
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, PR China
| | - Yongchao Liang
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, PR China
| | - Jingquan Yu
- Department of Horticulture, College of Agricultural and Biotechnology, Zhejiang University, Hangzhou 310058, PR China
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Peng HY, Qi YP, Lee J, Yang LT, Guo P, Jiang HX, Chen LS. Proteomic analysis of Citrus sinensis roots and leaves in response to long-term magnesium-deficiency. BMC Genomics 2015; 16:253. [PMID: 25887480 PMCID: PMC4383213 DOI: 10.1186/s12864-015-1462-z] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Accepted: 03/09/2015] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Magnesium (Mg)-deficiency is frequently observed in Citrus plantations and is responsible for the loss of productivity and poor fruit quality. Knowledge on the effects of Mg-deficiency on upstream targets is scarce. Seedlings of 'Xuegan' [Citrus sinensis (L.) Osbeck] were irrigated with Mg-deficient (0 mM MgSO4) or Mg-sufficient (1 mM MgSO4) nutrient solution for 16 weeks. Thereafter, we first investigated the proteomic responses of C. sinensis roots and leaves to Mg-deficiency using two-dimensional electrophoresis (2-DE) in order to (a) enrich our understanding of the molecular mechanisms of plants to deal with Mg-deficiency and (b) understand the molecular mechanisms by which Mg-deficiency lead to a decrease in photosynthesis. RESULTS Fifty-nine upregulated and 31 downregulated protein spots were isolated in Mg-deficient leaves, while only 19 upregulated and 12 downregulated protein spots in Mg-deficient roots. Many Mg-deficiency-responsive proteins were involved in carbohydrate and energy metabolism, followed by protein metabolism, stress responses, nucleic acid metabolism, cell wall and cytoskeleton metabolism, lipid metabolism and cell transport. The larger changes in leaf proteome versus root one in response to Mg-deficiency was further supported by our observation that total soluble protein concentration was decreased by Mg-deficiency in leaves, but unaffected in roots. Mg-deficiency had decreased levels of proteins [i.e. ribulose-1,5-bisphosphate carboxylase (Rubisco), rubisco activase, oxygen evolving enhancer protein 1, photosynthetic electron transfer-like protein, ferredoxin-NADP reductase (FNR), aldolase] involved in photosynthesis, thus decreasing leaf photosynthesis. To cope with Mg-deficiency, C. sinensis leaves and roots might respond adaptively to Mg-deficiency through: improving leaf respiration and lowering root respiration, but increasing (decreasing) the levels of proteins related to ATP synthase in roots (leaves); enhancing the levels of proteins involved in reactive oxygen species (ROS) scavenging and other stress-responsive proteins; accelerating proteolytic cleavage of proteins by proteases, protein transport and amino acid metabolism; and upregulating the levels of proteins involved in cell wall and cytoskeleton metabolism. CONCLUSIONS Our results demonstrated that proteomics were more affected by long-term Mg-deficiency in leaves than in roots, and that the adaptive responses differed between roots and leaves when exposed to long-term Mg-deficiency. Mg-deficiency decreased the levels of many proteins involved in photosynthesis, thus decreasing leaf photosynthesis.
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Affiliation(s)
- Hao-Yang Peng
- College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
- College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
- Institute of Horticultural Plant Physiology, Biochemistry, and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
| | - Yi-Ping Qi
- Institute of Materia Medica, Fujian Academy of Medical Sciences, Fuzhou, 350001, China.
| | - Jinwook Lee
- Department of Horticultural Science, Kyungpook National University, Daegu, 702-701, ROK.
| | - Lin-Tong Yang
- College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
- Institute of Horticultural Plant Physiology, Biochemistry, and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
| | - Peng Guo
- College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
- Institute of Horticultural Plant Physiology, Biochemistry, and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
| | - Huan-Xin Jiang
- College of Life Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
- Institute of Horticultural Plant Physiology, Biochemistry, and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
| | - Li-Song Chen
- College of Resource and Environmental Science, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
- Institute of Horticultural Plant Physiology, Biochemistry, and Molecular Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
- Fujian Key Laboratory for Plant Molecular and Cell Biology, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
- The Higher Educational Key Laboratory of Fujian Province for Soil Ecosystem Health and Regulation, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
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Mileshina D, Niazi AK, Wyszko E, Szymanski M, Val R, Valentin C, Barciszewski J, Dietrich A. Mitochondrial targeting of catalytic RNAs. Methods Mol Biol 2015; 1265:227-54. [PMID: 25634279 DOI: 10.1007/978-1-4939-2288-8_17] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Genetic transformation of mitochondria in multicellular eukaryotes has remained inaccessible, hindering fundamental investigations and applications to gene therapy or biotechnology. In this context, we have developed a strategy to target nuclear transgene-encoded RNAs into mitochondria in plants. We describe here mitochondrial targeting of trans-cleaving ribozymes destined to knockdown organelle RNAs for regulation studies and inverse genetics and biotechnological purposes. The design and functional assessment of chimeric RNAs combining the ribozyme and the mitochondrial shuttle are detailed, followed by all procedures to prepare constructs for in vivo expression, generate stable plant transformants, and establish target RNA knockdown in mitochondria.
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Affiliation(s)
- Daria Mileshina
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084, Strasbourg, France
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8
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Igamberdiev AU, Kleczkowski LA. Optimization of ATP synthase function in mitochondria and chloroplasts via the adenylate kinase equilibrium. FRONTIERS IN PLANT SCIENCE 2015; 6:10. [PMID: 25674099 PMCID: PMC4309032 DOI: 10.3389/fpls.2015.00010] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 01/06/2015] [Indexed: 05/09/2023]
Abstract
The bulk of ATP synthesis in plants is performed by ATP synthase, the main bioenergetics engine of cells, operating both in mitochondria and in chloroplasts. The reaction mechanism of ATP synthase has been studied in detail for over half a century; however, its optimal performance depends also on the steady delivery of ATP synthase substrates and the removal of its products. For mitochondrial ATP synthase, we analyze here the provision of stable conditions for (i) the supply of ADP and Mg(2+), supported by adenylate kinase (AK) equilibrium in the intermembrane space, (ii) the supply of phosphate via membrane transporter in symport with H(+), and (iii) the conditions of outflow of ATP by adenylate transporter carrying out the exchange of free adenylates. We also show that, in chloroplasts, AK equilibrates adenylates and governs Mg(2+) contents in the stroma, optimizing ATP synthase and Calvin cycle operation, and affecting the import of inorganic phosphate in exchange with triose phosphates. It is argued that chemiosmosis is not the sole component of ATP synthase performance, which also depends on AK-mediated equilibrium of adenylates and Mg(2+), adenylate transport, and phosphate release and supply.
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Affiliation(s)
- Abir U. Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John’s, NL, Canada
- *Correspondence: Abir U. Igamberdiev, Department of Biology, Memorial University of Newfoundland, St. John’s, NL A1B3X9, Canada e-mail:
| | - Leszek A. Kleczkowski
- Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, Umeå, Sweden
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Niu Y, Chai R, Liu L, Jin G, Liu M, Tang C, Zhang Y. Magnesium availability regulates the development of root hairs in Arabidopsis thaliana (L.) Heynh. PLANT, CELL & ENVIRONMENT 2014; 37:2795-813. [PMID: 24851702 DOI: 10.1111/pce.12362] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 01/27/2014] [Accepted: 04/16/2014] [Indexed: 05/06/2023]
Abstract
Root hairs are reported to be plastic in response to nutrient supply, but relatively little is known about their development in response to magnesium (Mg) availability. Here, we showed that development of root hairs of Arabidopsis decreased progressively with increasing Mg supply, which was related to the initiation of new trichoblast files and likelihood of trichoblasts to form hairs. Tip-focused reactive oxygen species (ROS) and cytosolic Ca(2+) concentrations [(Ca(2+) )c] during elongation of root hairs were enhanced under low Mg but decreased under high Mg. Under low Mg, application of diphenylene iodonium (DPI) or BAPTA [1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid] blocked the enhanced development of root hairs and the opposite was true when the plants under high Mg were treated with phenazine methosulphate (PMS), methyl viologen (MV) or CaCl2 . Furthermore, Mg availability did not alter root hair growth in rhd2-1 mutant that contains lower levels of ROS and cytosolic [Ca(2+) ]c. Transcriptome data and qPCR results revealed a greater fraction of morphogenetic H-genes, and cell wall organization genes were up-regulated by low Mg but down-regulated by high Mg. Our data suggest a profound effect of Mg supply on the development of root hairs in Arabidopsis, through the characterized Ca(2+) and ROS signals that modulate the elongation of root hairs and the expression of root-hair morphogenetic genes.
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Affiliation(s)
- Yaofang Niu
- Ministry of Education Key Laboratory of Environmental Remediation and Ecosystem Health, College of Environmental and Resources Sciences, Zhejiang University, Hangzhou, 310058, China; Department of Horticulture, College of Agronomy and Biotechnology, Zhejiang University, Hangzhou, 310058, China
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10
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Interplay of Mg2+, ADP, and ATP in the cytosol and mitochondria: unravelling the role of Mg2+ in cell respiration. Proc Natl Acad Sci U S A 2014; 111:E4560-7. [PMID: 25313036 DOI: 10.1073/pnas.1406251111] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In animal and plant cells, the ATP/ADP ratio and/or energy charge are generally considered key parameters regulating metabolism and respiration. The major alternative issue of whether the cytosolic and mitochondrial concentrations of ADP and ATP directly mediate cell respiration remains unclear, however. In addition, because only free nucleotides are exchanged by the mitochondrial ADP/ATP carrier, whereas MgADP is the substrate of ATP synthase (EC 3.6.3.14), the cytosolic and mitochondrial Mg(2+) concentrations must be considered as well. Here we developed in vivo/in vitro techniques using (31)P-NMR spectroscopy to simultaneously measure these key components in subcellular compartments. We show that heterotrophic sycamore (Acer pseudoplatanus L.) cells incubated in various nutrient media contain low, stable cytosolic ADP and Mg(2+) concentrations, unlike ATP. ADP is mainly free in the cytosol, but complexed by Mg(2+) in the mitochondrial matrix, where [Mg(2+)] is tenfold higher. In contrast, owing to a much higher affinity for Mg(2+), ATP is mostly complexed by Mg(2+) in both compartments. Mg(2+) starvation used to alter cytosolic and mitochondrial [Mg(2+)] reversibly increases free nucleotide concentration in the cytosol and matrix, enhances ADP at the expense of ATP, decreases coupled respiration, and stops cell growth. We conclude that the cytosolic ADP concentration, and not ATP, ATP/ADP ratio, or energy charge, controls the respiration of plant cells. The Mg(2+) concentration, remarkably constant and low in the cytosol and tenfold higher in the matrix, mediates ADP/ATP exchange between the cytosol and matrix, [MgADP]-dependent mitochondrial ATP synthase activity, and cytosolic free ADP homeostasis.
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Dorion S, Rivoal J. Clues to the functions of plant NDPK isoforms. Naunyn Schmiedebergs Arch Pharmacol 2014; 388:119-32. [PMID: 24964975 DOI: 10.1007/s00210-014-1009-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Accepted: 06/15/2014] [Indexed: 12/20/2022]
Abstract
This review describes the five nucleoside diphosphate kinase (NDPK) genes found in both model plants Arabidopsis thaliana (thale cress) and Oryza sativa L. (rice). Phylogenetic and sequence analyses of these genes allow the definition of four types of NDPK isoforms with different predicted subcellular localization. These predictions are supported by experimental evidence for most NDPK types. Data mining also provides evidence for the existence of a novel NDPK type putatively localized in the endoplasmic reticulum. Phylogenic analyses indicate that plant types I, II, and III belong to the previously identified Nme group I whereas type IV belongs to Nme group II. Additional analysis of the literature offers clues supporting the idea that the various plant NDPK types have different functions. Hence, cytosolic type I NDPKs are involved in metabolism, growth, and stress responses. Type II NDPKs are localized in the chloroplast and mainly involved in photosynthetic development and oxidative stress management. Type III NDPKs have dual targeting to the mitochondria and the chloroplast and are principally involved in energy metabolism. The subcellular localization and precise function of the novel type IV NDPKs, however, will require further investigations.
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Affiliation(s)
- Sonia Dorion
- IRBV, Université de Montréal, 4101 rue Sherbrooke est, Montréal, QC, H1X 2B2, Canada
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12
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Hermans C, Conn SJ, Chen J, Xiao Q, Verbruggen N. An update on magnesium homeostasis mechanisms in plants. Metallomics 2014; 5:1170-83. [PMID: 23420558 DOI: 10.1039/c3mt20223b] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Worldwide, nearly two-thirds of the population do not consume the recommended amount of magnesium (Mg) in their diet. Furthermore, low Mg status (hypomagnesaemia) is known to contribute to a number of human chronic disease conditions. Because the principal dietary Mg source is of plant origin, agronomic and genetic biofortification strategies are aimed at improving nutritional Mg content in food crops to overcome this mineral deficiency in humans. This update incorporates the contributions of annotated permeases involved in Mg uptake, storage and recycling with a schematic model of Mg movement at the organ and cellular levels in the model species Arabidopsis thaliana. Furthermore, approaches using mutagenesis or natural ionomic variation to identify loci involved in Mg homeostasis in roots, leaves and seeds will be summarised. A brief overview will be presented on how Arabidopsis research can help to develop strategies for biofortification of crops.
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Affiliation(s)
- Christian Hermans
- Laboratory of Plant Physiology and Molecular Genetics, Université Libre de Bruxelles, Campus Plaine CP 242, Bd du Triomphe, 1050 Brussels, Belgium.
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13
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Bykova NV, Møller IM, Gardeström P, Igamberdiev AU. The function of glycine decarboxylase complex is optimized to maintain high photorespiratory flux via buffering of its reaction products. Mitochondrion 2014; 19 Pt B:357-64. [PMID: 24444663 DOI: 10.1016/j.mito.2014.01.001] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 01/09/2014] [Accepted: 01/10/2014] [Indexed: 12/29/2022]
Abstract
Oxidation of glycine in photorespiratory pathway is the major flux through mitochondria of C3 plants in the light. It sustains increased intramitochondrial concentrations of NADH and NADPH, which are required to engage the internal rotenone-insensitive NAD(P)H dehydrogenases and the alternative oxidase. We discuss here possible mechanisms of high photorespiratory flux maintenance in mitochondria and suggest that it is fulfilled under conditions where the concentrations of glycine decarboxylase reaction products NADH and CO2 achieve an equilibrium provided by malate dehydrogenase and carbonic anhydrase, respectively. This results in the removal of these products from the glycine decarboxylase multienzyme active sites and in the maintenance of their concentrations at levels sufficiently low to prevent substrate inhibition of the reaction.
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Affiliation(s)
- Natalia V Bykova
- Cereal Research Centre, Agriculture and Agri-Food Canada, Winnipeg, MB, R3T 2M9, Canada
| | - Ian M Møller
- Department of Molecular Biology and Genetics, Aarhus University, DK-4200 Slagelse, Denmark
| | - Per Gardeström
- Department of Plant Physiology, Umeå Plant Science Centre, University of Umeå, S-901 87 Umeå, Sweden
| | - Abir U Igamberdiev
- Department of Biology, Memorial University of Newfoundland, St. John's, NL, A1B 3X9, Canada.
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14
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Gifford JL, Jamshidiha M, Mo J, Ishida H, Vogel HJ. Comparing the calcium binding abilities of two soybean calmodulins: towards understanding the divergent nature of plant calmodulins. THE PLANT CELL 2013; 25:4512-24. [PMID: 24254124 PMCID: PMC3875733 DOI: 10.1105/tpc.113.113183] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 10/03/2013] [Accepted: 10/23/2013] [Indexed: 05/23/2023]
Abstract
The discovery that plants contain multiple calmodulin (CaM) isoforms of variable sequence identity to animal CaM suggested an additional level of sophistication in the intracellular role of calcium regulation in plants. Past research has focused on the ability of conserved or divergent plant CaM isoforms to activate both mammalian and plant protein targets. At present, however, not much is known about how these isoforms respond to the signal of an increased cytosolic calcium concentration. Here, using isothermal titration calorimetry and NMR spectroscopy, we investigated the calcium binding properties of a conserved (CaM1) and a divergent (CaM4) CaM isoform from soybean (Glycine max). Both isoforms bind calcium with a semisequential pathway that favors the calcium binding EF-hands of the C-terminal lobe over those of the N-terminal lobe. From the measured dissociation constants, CaM4 binds calcium with a threefold greater affinity than CaM1 (K(d,Ca,mean) of 5.0 versus 14.9 μM) but has a significantly reduced selectivity against the chemically similar magnesium cation that binds preferentially to EF-hand I of both isoforms. The implications of a potential magnesium/calcium competition on the activation of CaM1 and CaM4 are discussed in context with their ability to respond to stimulus-specific calcium signatures and their known physiological roles.
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Affiliation(s)
- Jessica L. Gifford
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary T2N 1N4, Calgary, Alberta, Canada
| | - Mostafa Jamshidiha
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary T2N 1N4, Calgary, Alberta, Canada
| | - Jeffrey Mo
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary T2N 1N4, Calgary, Alberta, Canada
| | - Hiroaki Ishida
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary T2N 1N4, Calgary, Alberta, Canada
| | - Hans J. Vogel
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary T2N 1N4, Calgary, Alberta, Canada
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15
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Feng X, Yang R, Zheng X, Zhang F. Identification of a novel nuclear-localized adenylate kinase 6 from Arabidopsis thaliana as an essential stem growth factor. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2012; 61:180-186. [PMID: 23121860 DOI: 10.1016/j.plaphy.2012.10.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Accepted: 10/04/2012] [Indexed: 05/27/2023]
Abstract
Adenylate kinase (AK; EC 2.7.4.3) is highly conserved across a wide range of organisms, including Saccharomyces cerevisiae, Caenorhabditis elegans, Drosophila melanogaster, Arabidopsis thaliana, and Homo sapiens. While AK6 orthologs play important roles in the growth of yeast and worms, the physiological function of AK6 in A. thaliana is still unknown. In this study, we first cloned and expressed Arabidopsis adenylate kinase 6 (AAK6). Enzyme assays revealed that AAK6 has characteristic adenylate kinase properties, with ATP as the preferred phosphate donor and AMP as the best phosphate acceptor. A subcellular localization assay demonstrated that AAK6 had a predominant nuclear localization. Through biochemical purification and mass spectrometry analysis, a putative homolog of the S. cerevisiae Rps14 protein was identified as a partner of AAK6. Most importantly, we observed that aak6 T-DNA insertion mutants had decreased stem growth compared with wild-type plants. These data indicate that AAK6 exhibits adenylate kinase activity and is an essential growth factor in Arabidopsis.
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Affiliation(s)
- Xue Feng
- Capital Normal University Affiliated Li Ze Middle School, Beijing 100071, China
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16
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Dinç E, Ceppi MG, Tóth SZ, Bottka S, Schansker G. The chl a fluorescence intensity is remarkably insensitive to changes in the chlorophyll content of the leaf as long as the chl a/b ratio remains unaffected. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:770-9. [PMID: 22342617 DOI: 10.1016/j.bbabio.2012.02.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Revised: 12/23/2011] [Accepted: 02/02/2012] [Indexed: 10/14/2022]
Abstract
The effects of changes in the chlorophyll (chl) content on the kinetics of the OJIP fluorescence transient were studied using two different approaches. An extensive chl loss (up to 5-fold decrease) occurs in leaves suffering from either an Mg(2+) or SO(4)(2-) deficiency. The effects of these treatments on the chl a/b ratio, which is related to antenna size, were very limited. This observation was confirmed by the identical light intensity dependencies of the K, J and I-steps of the fluorescence rise for three of the four treatments and by the absence of changes in the F(685 nm)/F(695 nm)-ratio of fluorescence emission spectra measured at 77K. Under these conditions, the F(0) and F(M)-values were essentially insensitive to the chl content. A second experimental approach consisted of the treatment of wheat leaves with specifically designed antisense oligodeoxynucleotides that interfered with the translation of mRNA of the genes coding for chl a/b binding proteins. This way, leaves with a wide range of chl a/b ratios were created. Under these conditions, an inverse proportional relationship between the F(M) values and the chl a/b ratio was observed. A strong effect of the chl a/b ratio on the fluorescence intensity was also observed for barley Chlorina f2 plants that lack chl b. The data suggest that the chl a/b ratio (antenna size) is a more important determinant of the maximum fluorescence intensity than the chl content of the leaf.
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Affiliation(s)
- Emine Dinç
- Institute of Plant Biology, Biological Research Center, Hungarian Academy of Sciences, H-6701 Szeged, Hungary
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17
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Val R, Wyszko E, Valentin C, Szymanski M, Cosset A, Alioua M, Dreher TW, Barciszewski J, Dietrich A. Organelle trafficking of chimeric ribozymes and genetic manipulation of mitochondria. Nucleic Acids Res 2011; 39:9262-74. [PMID: 21768127 PMCID: PMC3241634 DOI: 10.1093/nar/gkr580] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2011] [Revised: 06/28/2011] [Accepted: 06/29/2011] [Indexed: 01/15/2023] Open
Abstract
With the expansion of the RNA world, antisense strategies have become widespread to manipulate nuclear gene expression but organelle genetic systems have remained aside. The present work opens the field to mitochondria. We demonstrate that customized RNAs expressed from a nuclear transgene and driven by a transfer RNA-like (tRNA-like) moiety are taken up by mitochondria in plant cells. The process appears to follow the natural tRNA import specificity, suggesting that translocation indeed occurs through the regular tRNA uptake pathway. Upon validation of the strategy with a reporter sequence, we developed a chimeric catalytic RNA composed of a specially designed trans-cleaving hammerhead ribozyme and a tRNA mimic. Organelle import of the chimeric ribozyme and specific target cleavage within mitochondria were demonstrated in transgenic tobacco cell cultures and Arabidopsis thaliana plants, providing the first directed knockdown of a mitochondrial RNA in a multicellular eukaryote. Further observations point to mitochondrial messenger RNA control mechanisms related to the plant developmental stage and culture conditions. Transformation of mitochondria is only accessible in yeast and in the unicellular alga Chlamydomonas. Based on the widespread tRNA import pathway, our data thus make a breakthrough for direct investigation and manipulation of mitochondrial genetics.
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Affiliation(s)
- Romain Val
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - Eliza Wyszko
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - Clarisse Valentin
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - Maciej Szymanski
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - Anne Cosset
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - Malek Alioua
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - Theo W. Dreher
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - Jan Barciszewski
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
| | - André Dietrich
- Institut de Biologie Moléculaire des Plantes, CNRS and Université de Strasbourg, 12 rue du Général Zimmer, 67084 Strasbourg, France, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61-704 Poznan, Poland and Department of Microbiology, Oregon State University, Corvallis, Oregon 97331-3804, USA
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18
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Igamberdiev AU, Kleczkowski LA. Optimization of CO₂fixation in photosynthetic cells via thermodynamic buffering. Biosystems 2010; 103:224-9. [PMID: 20933572 DOI: 10.1016/j.biosystems.2010.10.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2010] [Accepted: 10/01/2010] [Indexed: 11/19/2022]
Abstract
Stable operation of photosynthesis is based on the establishment of local equilibria of metabolites in the Calvin cycle. This concerns especially equilibration of stromal contents of adenylates and pyridine nucleotides and buffering of CO₂ concentration to prevent its depletion at the sites of Rubisco. Thermodynamic buffering that controls the homeostatic flux in the Calvin cycle is achieved by equilibrium enzymes such as glyceraldehyde phosphate dehydrogenase, transaldolase and transketolase. Their role is to prevent depletion of ribulose-1,5-bisphosphate, even at high [CO₂], and to maintain conditions where the only control is exerted by the CO₂ supply. Buffering of adenylates is achieved mainly by chloroplastic adenylate kinase, whereas NADPH level is maintained by mechanisms involving alternative sinks for electrons both within the chloroplast (cyclic phosphorylation, chlororespiration, etc.) and shuttling of reductants outside chloroplast (malate valve). This results in optimization of carbon fixation in chloroplasts, illustrating the principle that the energy of light is used to support stable non-equilibrium which drives all living processes in plants.
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Affiliation(s)
- Abir U Igamberdiev
- Department of Biology, Memorial University of Newfoundland, Main Campus, St. John's, NL A1B 3X9, Canada.
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19
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Igamberdiev AU, Kleczkowski LA. Metabolic systems maintain stable non-equilibrium via thermodynamic buffering. Bioessays 2009; 31:1091-9. [PMID: 19708023 DOI: 10.1002/bies.200900057] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Here, we analyze how the set of nucleotides in the cell is equilibrated and how this generates simple rules that help the cell to organize itself via maintenance of a stable non-equilibrium state. A major mechanism operating to achieve this state is thermodynamic buffering via high activities of equilibrating enzymes such as adenylate kinase. Under stable non-equilibrium, the ratios of free and Mg-bound adenylates, Mg(2+) and membrane potentials are interdependent and can be computed. The adenylate status is balanced with the levels of reduced and oxidized pyridine nucleotides through regulated uncoupling of the pyridine nucleotide pool from ATP production in mitochondria, and through oxidation of substrates non-coupled to NAD(+) reduction in peroxisomes. The set of adenylates and pyridine nucleotides constitutes a generalized cell energy status and determines rates of major metabolic fluxes. As the result, fluxes of energy and information become organized spatially and temporally, providing conditions for self-maintenance of metabolism.
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20
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Tan YW, Hanson JA, Yang H. Direct Mg(2+) binding activates adenylate kinase from Escherichia coli. J Biol Chem 2009; 284:3306-3313. [PMID: 19029291 PMCID: PMC3837426 DOI: 10.1074/jbc.m803658200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2008] [Revised: 11/07/2008] [Indexed: 01/23/2023] Open
Abstract
We report evidence that adenylate kinase (AK) from Escherichia coli can be activated by the direct binding of a magnesium ion to the enzyme, in addition to ATP-complexed Mg(2+). By systematically varying the concentrations of AMP, ATP, and magnesium in kinetic experiments, we found that the apparent substrate inhibition of AK, formerly attributed to AMP, was suppressed at low magnesium concentrations and enhanced at high magnesium concentrations. This previously unreported magnesium dependence can be accounted for by a modified random bi-bi model in which Mg(2+) can bind to AK directly prior to AMP binding. A new kinetic model is proposed to replace the conventional random bi-bi mechanism with substrate inhibition and is able to describe the kinetic data over a physiologically relevant range of magnesium concentrations. According to this model, the magnesium-activated AK exhibits a 23- +/- 3-fold increase in its forward reaction rate compared with the unactivated form. The findings imply that Mg(2+) could be an important affecter in the energy signaling network in cells.
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Affiliation(s)
- Yan-Wen Tan
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720
| | - Jeffrey A Hanson
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720
| | - Haw Yang
- Department of Chemistry, University of California at Berkeley, Berkeley, California 94720; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720.
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21
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RACK1 Inhibits TRPM6 Activity via Phosphorylation of the Fused α-Kinase Domain. Curr Biol 2008; 18:168-76. [DOI: 10.1016/j.cub.2007.12.058] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Revised: 11/23/2007] [Accepted: 12/21/2007] [Indexed: 02/07/2023]
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22
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Cookson SJ, Williams LE, Miller AJ. Light-dark changes in cytosolic nitrate pools depend on nitrate reductase activity in Arabidopsis leaf cells. PLANT PHYSIOLOGY 2005; 138:1097-105. [PMID: 15908593 PMCID: PMC1150423 DOI: 10.1104/pp.105.062349] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Several different cellular processes determine the size of the metabolically available nitrate pool in the cytoplasm. These processes include not only ion fluxes across the plasma membrane and tonoplast but also assimilation by the activity of nitrate reductase (NR). In roots, the maintenance of cytosolic nitrate activity during periods of nitrate starvation and resupply (M. van der Leij, S.J. Smith, A.J. Miller [1998] Planta 205: 64-72; R.-G. Zhen, H.-W. Koyro, R.A. Leigh, A.D. Tomos, A.J. Miller [1991] Planta 185: 356-361) suggests that this pool is regulated. Under nitrate-replete conditions vacuolar nitrate is a membrane-bound store that can release nitrate to the cytoplasm; after depletion of cytosolic nitrate, tonoplast transporters would serve to restore this pool. To study the role of assimilation, specifically the activity of NR in regulating the size of the cytosolic nitrate pool, we have compared wild-type and mutant plants. In leaf mesophyll cells, light-to-dark transitions increase cytosolic nitrate activity (1.5-2.8 mm), and these changes were reversed by dark-to-light transitions. Such changes were not observed in nia1nia2 NR-deficient plants indicating that this change in cytosolic nitrate activity was dependent on the presence of functional NR. Furthermore, in the dark, the steady-state cytosolic nitrate activities were not statistically different between the two types of plant, indicating that NR has little role in determining resting levels of nitrate. Epidermal cells of both wild type and NR mutants had cytosolic nitrate activities that were not significantly different from mesophyll cells in the dark and were unaltered by dark-to-light transitions. We propose that the NR-dependent changes in cytosolic nitrate provide a cellular mechanism for the diurnal changes in vacuolar nitrate storage, and the results are discussed in terms of the possible signaling role of cytosolic nitrate.
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Affiliation(s)
- Sarah J Cookson
- School of Biological Sciences, University of Southampton, Southampton SO16 7PX, United Kingdom
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23
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Bustos DM, Iglesias AA. A model for the interaction between plant GAPN and 14-3-3ζ using protein–protein docking calculations, electrostatic potentials and kinetics. J Mol Graph Model 2005; 23:490-502. [PMID: 15896993 DOI: 10.1016/j.jmgm.2005.03.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2004] [Revised: 03/25/2005] [Accepted: 03/29/2005] [Indexed: 10/25/2022]
Abstract
Phosphorylated non-phosphorylating glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.9; GAPN) found in heterotrophic cells of wheat is activated by MgCl(2). The divalent cation disrupts the interaction between GAPN and a 14-3-3 regulatory protein. This effect is quite remarkable, since it has previously been shown that 14-3-3 binding to a target protein requires divalent cations as Mg(2+) or Ca(2+). Binding of the divalent cation to 14-3-3 causes an increase in surface hydrophobicity. Crystal structure of a 14-3-3-target protein complex has been only determined for serotinin N-acetyltransferase. We utilized a model of a subunit of plant GAPN and the crystallographic structure of human 14-3-3zeta to shape the complex between theses two proteins. Initial dockings were performed with the BiGGER program, which allows an exhaustive search of translational and rotational space. A filtering procedure was then applied to reduce the number of complexes to a manageable number. We predict the structural characteristics of GAPN-14-3-3zeta binding process, proposing that the main attractive force in this complex derives from electrostatic interactions. The predicted model was corroborated by analysis of kinetic behavior of GAPN and its relationship with pH and ionic strength conditions. This study provides a variant on the interaction of 14-3-3 with target proteins, thus affording a wider scenario to establish possible structural models for this remarkable family of regulatory proteins.
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Affiliation(s)
- Diego M Bustos
- Instituto Tecnológico de Chascomús (IIB-INTECH), Camino Circunv, Laguna km 6, CC 164, B7130IWA Chascomús, Argentina
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24
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Pottosin II, Muñiz J, Shabala S. Fast-activating channel controls cation fluxes across the native chloroplast envelope. J Membr Biol 2005; 204:145-56. [PMID: 16245037 DOI: 10.1007/s00232-005-0758-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Revised: 06/20/2005] [Indexed: 11/28/2022]
Abstract
A prerequisite for photosynthetic CO(2) fixation is the maintenance of alkaline pH in the stroma. This is achieved by H(+) pumping from the stroma to the cytosol, electrically balanced by an influx of cations through some unidentified non-selective envelope channels. In this study, the patch-clamp technique was applied to isolated Pisum sativum L. (pea) chloroplasts, and a fast-activating chloroplast cation (FACC) channel was discovered in the native envelope. This channel opens within a few milliseconds upon voltage steps to large positive or negative potentials. Remarkably, the single-channel conductance increased fivefold, from approximately 40 pS to approximately 200 pS (symmetric 250 mM KCl), upon a potential change from zero to +/- 200 mV. The FACC channel conducts all physiologically essential inorganic cations (K(+), Na(+), Ca(2+), Mg(2+)) with little preference. An increase of stromal pH from 7.3 to 8.0, mimicking dark-light transition, caused about a 2-fold decrease of the FACC channel activity within a physiologically relevant potential range. The FACC channel was completely and irreversibly blocked by Gd(3+). Based on the estimated transport capacity of the whole chloroplast population of FACC channels together with the envelope H(+)-ATPases, these channels can mediate electroneutral K(+)/H(+) exchange across the envelope, enabling stroma alkalinization, thereby allowing an optimal photosynthetic performance.
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Affiliation(s)
- I I Pottosin
- Biomedical Center, University of Colima, 28045, Colima, Mexico
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25
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Hermans C, Johnson GN, Strasser RJ, Verbruggen N. Physiological characterisation of magnesium deficiency in sugar beet: acclimation to low magnesium differentially affects photosystems I and II. PLANTA 2004; 220:344-55. [PMID: 15378366 DOI: 10.1007/s00425-004-1340-4] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2004] [Accepted: 06/17/2004] [Indexed: 05/03/2023]
Abstract
Magnesium deficiency in plants is a widespread problem, affecting productivity and quality in agriculture, yet at a physiological level it has been poorly studied in crop plants. Here, a physiological characterization of Mg deficiency in Beta vulgaris L., an important crop model, is presented. The impact of Mg deficiency on plant growth, mineral profile and photosynthetic activity was studied. The aerial biomass of plants decreased after 24 days of hydroponic culture in Mg-free nutrient solution, whereas the root biomass was unaffected. Analysis of mineral profiles revealed that Mg decreased more rapidly in roots than in shoots and that shoot Mg content could fall to 3 mg g(-1) DW without chlorosis development and with no effect on photosynthetic parameters. Sucrose accumulated in most recently expanded leaves before any loss in photosynthetic activity. During the development of Mg deficiency, the two photosystems showed sharply contrasting responses. Data were consistent with a down-regulation of PSII through a loss of antenna, and of PSI primarily through a loss of reaction centres. In each case, the net result was a decrease in the overall rate of linear electron transport, preventing an excess of reductant being produced during conditions under which sucrose export away from mature leaf was restricted.
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Affiliation(s)
- Christian Hermans
- Laboratoire de Physiologie et de Génétique Moléculaire des Plantes, Université Libre de Bruxelles, 1050 Brussels, Belgium
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26
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Wei H, Atkins CA, Layzell DB. Adenylate gradients and Ar:O(2) effects on legume nodules: I. Mathematical models. PLANT PHYSIOLOGY 2004; 134:801-12. [PMID: 14739350 PMCID: PMC344555 DOI: 10.1104/pp.103.032318] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2003] [Revised: 09/26/2003] [Accepted: 11/10/2003] [Indexed: 05/20/2023]
Abstract
Mathematical models were developed to test the likelihood that large cytosolic adenylate concentration gradients exist across the bacteria-infected cells of legume nodules. Previous studies hypothesized that this may be the case to account for the unusually low adenylate energy charge (AEC; 0.65) measured in the plant fraction of metabolically active nodules (M.M. Kuzma, H. Winter, P. Storer, I. Oresnik, C.A. Atkins, D.B. Layzell [1999] Plant Physiol 119: 399-407). Simulations coupled leghemoglobin-facilitated O(2) diffusion into the infected cell, through bacteroid nitrogenase activity, with the ATP demand for transport and ammonia assimilation in the plant fraction of ureide- and amide-producing nodules. Although large cytosolic adenylate gradients were predicted to exist in both nodule types, amide nodules were predicted to have steeper AEC gradients (0.82-0.52) than ureide nodules (0.82-0.61). The differences were attributed to an additional ATP demand for Asn synthesis in the amide nodule. Simulations for nodules transferred to an Ar:O(2) atmosphere predicted a major reduction in the magnitude of adenylate gradients and an increase in the AEC of the plant fraction. Results were consistent with a number of experimental studies and were used to propose an experimental test of the models.
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Affiliation(s)
- Hui Wei
- Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6
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27
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Tovar-Méndez A, Miernyk JA, Randall DD. Regulation of pyruvate dehydrogenase complex activity in plant cells. EUROPEAN JOURNAL OF BIOCHEMISTRY 2003; 270:1043-9. [PMID: 12631264 DOI: 10.1046/j.1432-1033.2003.03469.x] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pyruvate dehydrogenase complex (PDC) is subjected to multiple interacting levels of control in plant cells. The first level is subcellular compartmentation. Plant cells are unique in having two distinct, spatially separated forms of the PDC; mitochondrial (mtPDC) and plastidial (plPDC). The mtPDC is the site of carbon entry into the tricarboxylic acid cycle, while the plPDC provides acetyl-CoA and NADH for de novo fatty acid biosynthesis. The second level of regulation of PDC activity is the control of gene expression. The genes encoding the subunits of the mt- and plPDCs are expressed following developmental programs, and are additionally subject to physiological and environmental cues. Thirdly, both the mt- and plPDCs are sensitive to product inhibition, and, potentially, to metabolite effectors. Finally, the two different forms of the complex are regulated by distinct organelle-specific mechanisms. Activity of the mtPDC is regulated by reversible phosphorylation catalyzed by intrinsic kinase and phosphatase components. An additional level of sensitivity is provided by metabolite control of the kinase activity. The plPDC is not regulated by reversible phosphorylation. Instead, activity is controlled to a large extent by the physical environment that exists in the plastid stroma.
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Affiliation(s)
- Alejandro Tovar-Méndez
- Department of Biochemistry, University of Missouri and Plant Genetics Research Unit, USDA, Agricultural Research Service, Columbia, MO 65211, USA
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28
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Huber SC, MacKintosh C, Kaiser WM. Metabolic enzymes as targets for 14-3-3 proteins. PLANT MOLECULAR BIOLOGY 2002; 50:1053-63. [PMID: 12516872 DOI: 10.1023/a:1021284002779] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The 14-3-3 proteins are binding proteins that have been shown to interact with a wide array of enzymes involved in primary biosynthetic and energy metabolism in plants. In most cases, the significance of binding of the 14-3-3 protein is not known. However, most of the interactions are phosphorylation-dependent and most of the known binding partners are found in the cytosol, while some may also be localized to plastids and mitochondria. In this review, we examine the factors that may regulate the binding of 14-3-3s to their target proteins, and discuss their possible roles in the regulation of the activity and proteolytic degradation of enzymes involved in primary carbon and nitrogen metabolism.
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Affiliation(s)
- Steven C Huber
- USDA/ARS and Department of Crop Science, North Carolina State University, Raleigh, NC 27695-7631, USA.
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