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Paz Y, Shimoni E, Weiss M, Pick U. Effects of iron deficiency on iron binding and internalization into acidic vacuoles in Dunaliella salina. PLANT PHYSIOLOGY 2007; 144:1407-15. [PMID: 17513481 PMCID: PMC1914149 DOI: 10.1104/pp.107.100644] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Uptake of iron in the halotolerant alga Dunaliella salina is mediated by a transferrin-like protein (TTf), which binds and internalizes Fe(3+) ions. Recently, we found that iron deficiency induces a large enhancement of iron binding, which is associated with accumulation of three other plasma membrane proteins that associate with TTf. In this study, we characterized the kinetic properties of iron binding and internalization and identified the site of iron internalization. Iron deficiency induces a 4-fold increase in Fe binding, but only 50% enhancement in the rate of iron uptake and also increases the affinity for iron and bicarbonate, a coligand for iron binding. These results indicate that iron deprivation leads to accumulation and modification of iron-binding sites. Iron uptake in iron-sufficient cells is preceded by an apparent time lag, resulting from prebound iron, which can be eliminated by unloading iron-binding sites. Iron is tightly bound to surface-exposed sites and hardly exchanges with medium iron. All bound iron is subsequently internalized. Accumulation of iron inhibits further iron binding and internalization. The vacuolar inhibitor bafilomycin inhibits iron uptake and internalization. Internalized iron was localized by electron microscopy within vacuolar structures that were identified as acidic vacuoles. Iron internalization is accompanied by endocytosis of surface proteins into these acidic vacuoles. A novel kinetic mechanism for iron uptake is proposed, which includes two pools of bound/compartmentalized iron separated by a rate-limiting internalization stage. The major parameter that is modulated by iron deficiency is the iron-binding capacity. We propose that excessive iron binding in iron-deficient cells serves as a temporary reservoir for iron that is subsequently internalized. This mechanism is particularly suitable for organisms that are exposed to large fluctuations in iron availability.
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Affiliation(s)
- Yakov Paz
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot, Israel
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102
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Palenik B, Grimwood J, Aerts A, Rouzé P, Salamov A, Putnam N, Dupont C, Jorgensen R, Derelle E, Rombauts S, Zhou K, Otillar R, Merchant SS, Podell S, Gaasterland T, Napoli C, Gendler K, Manuell A, Tai V, Vallon O, Piganeau G, Jancek S, Heijde M, Jabbari K, Bowler C, Lohr M, Robbens S, Werner G, Dubchak I, Pazour GJ, Ren Q, Paulsen I, Delwiche C, Schmutz J, Rokhsar D, Van de Peer Y, Moreau H, Grigoriev IV. The tiny eukaryote Ostreococcus provides genomic insights into the paradox of plankton speciation. Proc Natl Acad Sci U S A 2007; 104:7705-10. [PMID: 17460045 PMCID: PMC1863510 DOI: 10.1073/pnas.0611046104] [Citation(s) in RCA: 425] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The smallest known eukaryotes, at approximately 1-mum diameter, are Ostreococcus tauri and related species of marine phytoplankton. The genome of Ostreococcus lucimarinus has been completed and compared with that of O. tauri. This comparison reveals surprising differences across orthologous chromosomes in the two species from highly syntenic chromosomes in most cases to chromosomes with almost no similarity. Species divergence in these phytoplankton is occurring through multiple mechanisms acting differently on different chromosomes and likely including acquisition of new genes through horizontal gene transfer. We speculate that this latter process may be involved in altering the cell-surface characteristics of each species. In addition, the genome of O. lucimarinus provides insights into the unique metal metabolism of these organisms, which are predicted to have a large number of selenocysteine-containing proteins. Selenoenzymes are more catalytically active than similar enzymes lacking selenium, and thus the cell may require less of that protein. As reported here, selenoenzymes, novel fusion proteins, and loss of some major protein families including ones associated with chromatin are likely important adaptations for achieving a small cell size.
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Affiliation(s)
- Brian Palenik
- Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0202
- To whom correspondence may be addressed. E-mail: or
| | - Jane Grimwood
- Joint Genome Institute and Stanford Human Genome Center, Stanford University School of Medicine, 975 California Avenue, Palo Alto, CA 94304
| | - Andrea Aerts
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
| | - Pierre Rouzé
- Laboratoire Associé de l'Institut National de la Recherche Agronomique (France), Ghent University, Technologiepark 927, B-9052 Ghent, Belgium
| | - Asaf Salamov
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
| | - Nicholas Putnam
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
| | - Chris Dupont
- Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0202
| | - Richard Jorgensen
- Department of Plant Sciences, University of Arizona, 303 Forbes Building, Tucson, AZ 85721-0036
| | - Evelyne Derelle
- Observatoire Océanologique, Laboratoire Arago, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie Paris 6, Unité Mixte de Recherche 7628, BP 44, 66651 Banyuls sur Mer Cedex, France
| | - Stephane Rombauts
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium
| | - Kemin Zhou
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
| | - Robert Otillar
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
| | - Sabeeha S. Merchant
- Department of Chemistry and Biochemistry, University of California, Box 951569, Los Angeles, CA 90095
| | - Sheila Podell
- Scripps Genome Center, Scripps Institution of Oceanography, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0202
| | - Terry Gaasterland
- Scripps Genome Center, Scripps Institution of Oceanography, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0202
| | - Carolyn Napoli
- Department of Plant Sciences, University of Arizona, 303 Forbes Building, Tucson, AZ 85721-0036
| | - Karla Gendler
- Department of Plant Sciences, University of Arizona, 303 Forbes Building, Tucson, AZ 85721-0036
| | - Andrea Manuell
- Department of Cell Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037
| | - Vera Tai
- Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093-0202
| | - Olivier Vallon
- Institut de Biologie Physico-Chimique, Centre National de la Recherche Scientifique/Université Paris 6, Unité Mixte de Recherche 7141, 13, Rue Pierre et Marie Curie, 75005 Paris, France
| | - Gwenael Piganeau
- Observatoire Océanologique, Laboratoire Arago, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie Paris 6, Unité Mixte de Recherche 7628, BP 44, 66651 Banyuls sur Mer Cedex, France
| | - Séverine Jancek
- Observatoire Océanologique, Laboratoire Arago, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie Paris 6, Unité Mixte de Recherche 7628, BP 44, 66651 Banyuls sur Mer Cedex, France
| | - Marc Heijde
- Département de Biologie, Ecole Normale Supérieure, Formation de Recherche en Evolution 2910, Centre National de la Recherche Scientifique, 46, Rue D'Ulm, 75230 Paris Cedex 05, France
| | - Kamel Jabbari
- Département de Biologie, Ecole Normale Supérieure, Formation de Recherche en Evolution 2910, Centre National de la Recherche Scientifique, 46, Rue D'Ulm, 75230 Paris Cedex 05, France
| | - Chris Bowler
- Département de Biologie, Ecole Normale Supérieure, Formation de Recherche en Evolution 2910, Centre National de la Recherche Scientifique, 46, Rue D'Ulm, 75230 Paris Cedex 05, France
| | - Martin Lohr
- Institut für Allgemeine Botanik, Johannes Gutenberg-Universität, D-55099 Mainz, Germany
| | - Steven Robbens
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium
| | - Gregory Werner
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
| | - Inna Dubchak
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
| | - Gregory J. Pazour
- Program in Molecular Medicine, University of Massachusetts Medical School, Suite 213, Biotech II, 373 Plantation Street, Worcester, MA 01605
| | - Qinghu Ren
- The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850; and
| | - Ian Paulsen
- The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850; and
| | - Chuck Delwiche
- Cell Biology and Molecular Genetics, University of Maryland, H. J. Patterson Hall, Building 073, College Park, MD 20742-5815
| | - Jeremy Schmutz
- Joint Genome Institute and Stanford Human Genome Center, Stanford University School of Medicine, 975 California Avenue, Palo Alto, CA 94304
| | - Daniel Rokhsar
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
| | - Yves Van de Peer
- Department of Plant Systems Biology, Flanders Interuniversity Institute for Biotechnology, Ghent University, Technologiepark 927, B-9052 Ghent, Belgium
| | - Hervé Moreau
- Observatoire Océanologique, Laboratoire Arago, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie Paris 6, Unité Mixte de Recherche 7628, BP 44, 66651 Banyuls sur Mer Cedex, France
| | - Igor V. Grigoriev
- U.S. Department of Energy Joint Genome Institute, 2800 Mitchell Drive, Walnut Creek, CA 94598
- To whom correspondence may be addressed. E-mail: or
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103
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Krämer U, Talke IN, Hanikenne M. Transition metal transport. FEBS Lett 2007; 581:2263-72. [PMID: 17462635 DOI: 10.1016/j.febslet.2007.04.010] [Citation(s) in RCA: 272] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 04/02/2007] [Accepted: 04/03/2007] [Indexed: 11/26/2022]
Abstract
Transition metal transporters are of central importance in the plant metal homeostasis network which maintains internal metal concentrations within physiological limits. An overview is given of the functions of known transition metal transporters in the context of the unique chemical properties of their substrates. The modifications of the metal homeostasis network associated with the adaptation to an extreme metalliferous environment are illustrated in two Brassicaceae metal hyperaccumulator model plants based on cross-species transcriptomics studies. In a comparison between higher plants and unicellular algae, hypotheses are generated for evolutionary changes in metal transporter complements associated with the transition to multicellularity.
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Affiliation(s)
- Ute Krämer
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, D-14476, Potsdam/Golm, Germany.
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104
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Puig S, Andrés-Colás N, García-Molina A, Peñarrubia L. Copper and iron homeostasis in Arabidopsis: responses to metal deficiencies, interactions and biotechnological applications. PLANT, CELL & ENVIRONMENT 2007; 30:271-290. [PMID: 17263774 DOI: 10.1111/j.1365-3040.2007.01642.x] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Plants have developed sophisticated mechanisms to tightly control the acquisition and distribution of copper and iron in response to environmental fluctuations. Recent studies with Arabidopsis thaliana are allowing the characterization of the diverse families and components involved in metal uptake, such as metal-chelate reductases and plasma membrane transporters. In parallel, emerging data on both intra- and intercellular metal distribution, as well as on long-distance transport, are contributing to the understanding of metal homeostatic networks in plants. Furthermore, gene expression analyses are deciphering coordinated mechanisms of regulation and response to copper and iron limitation. Prioritizing the use of metals in essential versus dispensable processes, and substituting specific metalloproteins by other metal counterparts, are examples of plant strategies to optimize copper and iron utilization. The metabolic links between copper and iron homeostasis are well documented in yeast, algae and mammals. In contrast, interactions between both metals in vascular plants remain controversial, mainly owing to the absence of copper-dependent iron acquisition. This review describes putative interactions between both metals at different levels in plants. The characterization of plant copper and iron homeostasis should lead to biotechnological applications aimed at the alleviation of iron deficiency and copper contamination and, thus, have a beneficial impact on agricultural and human health problems.
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Affiliation(s)
- Sergi Puig
- Departament de Bioquímica i Biologia Molecular. Universitat de València. Av. Doctor Moliner, 50 E-46100 Burjassot, Valencia, Spain
| | - Nuria Andrés-Colás
- Departament de Bioquímica i Biologia Molecular. Universitat de València. Av. Doctor Moliner, 50 E-46100 Burjassot, Valencia, Spain
| | - Antoni García-Molina
- Departament de Bioquímica i Biologia Molecular. Universitat de València. Av. Doctor Moliner, 50 E-46100 Burjassot, Valencia, Spain
| | - Lola Peñarrubia
- Departament de Bioquímica i Biologia Molecular. Universitat de València. Av. Doctor Moliner, 50 E-46100 Burjassot, Valencia, Spain
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105
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Paz Y, Katz A, Pick U. A Multicopper Ferroxidase Involved in Iron Binding to Transferrins in Dunaliella salina Plasma Membranes. J Biol Chem 2007; 282:8658-66. [PMID: 17227764 DOI: 10.1074/jbc.m609756200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The halotolerant alga Dunaliella salina is unique among plants in that it utilizes a transferrin (TTf) to mediate iron acquisition (Fisher, M., Zamir, A., and Pick, U. (1998) J. Biol. Chem. 273, 17553-17558). Two new proteins that are induced by iron deprivation were identified in plasma membranes of D. salina as follows: a multicopper ferroxidase termed D-Fox and an internally duplicated glycoprotein (p130B). D-Fox and p130B are accessible to glycolytic, proteolytic, and biotin surface tagging treatments, suggesting that they are surface-exposed glycoproteins. Induction of D-Fox was also manifested by ferroxidase activity in plasma membrane preparations. These results are puzzling because ferroxidases in yeast and in Chlamydomonas reinhardtii function in redox-mediated iron uptake, a mechanism that is not known to operate in D. salina. Two lines of evidence suggest that D-Fox and p130B interact with D. salina triplicated transferrin (TTf). First, chemical cross-linking combined with mass spectroscopy analysis showed that D-Fox and p130B associate with TTf and with another plasma membrane transferrin. Second, detergent-solubilized D-Fox and p130B comigrated on blue native gels with plasma membrane transferrins. 59Fe autoradiography indicated that this complex binds Fe3+ ions. Also, the induction of D-Fox and p130B is kinetically correlated with enhanced iron binding and uptake activities. These results suggest that D-Fox and p130B associate with plasma membrane transferrins forming a complex that enhances iron binding and iron uptake. We propose that the function of D-Fox in D. salina has been modified during evolution from redox-mediated to transferrin-mediated iron uptake, following a gene transfer event of transferrins from an ancestral animal cell.
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Affiliation(s)
- Yakov Paz
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
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106
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Allen MD, Kropat J, Tottey S, Del Campo JA, Merchant SS. Manganese deficiency in Chlamydomonas results in loss of photosystem II and MnSOD function, sensitivity to peroxides, and secondary phosphorus and iron deficiency. PLANT PHYSIOLOGY 2007; 143:263-77. [PMID: 17085511 PMCID: PMC1761973 DOI: 10.1104/pp.106.088609] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
For photoheterotrophic growth, a Chlamydomonas reinhardtii cell requires at least 1.7 x 10(7) manganese ions in the medium. At lower manganese ion concentrations (typically <0.5 microm), cells divide more slowly, accumulate less chlorophyll, and the culture reaches stationary phase at lower cell density. Below 0.1 microm supplemental manganese ion in the medium, the cells are photosynthetically defective. This is accompanied by decreased abundance of D1, which binds the Mn(4)Ca cluster, and release of the OEE proteins from the membrane. Assay of Mn superoxide dismutase (MnSOD) indicates loss of activity of two isozymes in proportion to the Mn deficiency. The expression of MSD3 through MSD5, encoding various isoforms of the MnSODs, is up-regulated severalfold in Mn-deficient cells, but neither expression nor activity of the plastid Fe-containing superoxide dismutase is changed, which contrasts with the dramatically increased MSD3 expression and plastid MnSOD activity in Fe-deficient cells. Mn-deficient cells are selectively sensitive to peroxide but not methyl viologen or Rose Bengal, and GPXs, APX, and MSRA2 genes (encoding glutathione peroxidase, ascorbate peroxidase, and methionine sulfoxide reductase 2) are slightly up-regulated. Elemental analysis indicates that the Mn, Fe, and P contents of cells in the Mn-deficient cultures were reduced in proportion to the deficiency. A natural resistance-associated macrophage protein homolog and one of five metal tolerance proteins were induced in Mn-deficient cells but not in Fe-deficient cells, suggesting that the corresponding gene products may be components of a Mn(2+)-selective assimilation pathway.
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Affiliation(s)
- Michael D Allen
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA
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107
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108
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Pilon M, Abdel-Ghany SE, Cohu CM, Gogolin KA, Ye H. Copper cofactor delivery in plant cells. CURRENT OPINION IN PLANT BIOLOGY 2006; 9:256-63. [PMID: 16616609 DOI: 10.1016/j.pbi.2006.03.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Accepted: 03/22/2006] [Indexed: 05/08/2023]
Abstract
Copper (Cu) is a micronutrient that has roles in photosynthesis, respiration, antioxidant activity, cell wall metabolism and hormone perception. Excess Cu is toxic and therefore its delivery has to be tightly regulated. Recent progress in the study of Cu homeostasis has revealed not only components of the Cu delivery machinery but also regulatory systems that control Cu-protein expression and coordinate the activity of Cu-delivery systems. The response of photosynthetic organisms to Cu deficiency indicates the existence of cross-talk between metal cofactor delivery pathways. Next to its well-established roles in plant metabolism, a novel function for Cu, first discovered in plants, is in the biogenesis of molybdenum cofactor. Defects in Cu delivery factors also suggest important roles for Cu in cell expansion.
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Affiliation(s)
- Marinus Pilon
- Biology Department and Program in Molecular Plant Biology, Colorado State University, Fort Collins, Colorado 80523-1878, USA.
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109
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Chen H, Huang G, Su T, Gao H, Attieh ZK, McKie AT, Anderson GJ, Vulpe CD. Decreased hephaestin activity in the intestine of copper-deficient mice causes systemic iron deficiency. J Nutr 2006; 136:1236-41. [PMID: 16614410 DOI: 10.1093/jn/136.5.1236] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Copper and iron metabolism intersect in mammals. Copper deficiency simultaneously leads to decreased iron levels in some tissues and iron deficiency anemia, whereas it results in iron overload in other tissues such as the intestine and liver. The copper requirement of the multicopper ferroxidases hephaestin and ceruloplasmin likely explains this link between copper and iron homeostasis in mammals. We investigated the effect of in vivo and in vitro copper deficiency on hephaestin (Heph) expression and activity. C57BL/6J mice were separated into 2 groups on the day of parturition. One group was fed a copper-deficient diet and another was fed a control diet for 6 wk. Copper-deficient mice had significantly lower hephaestin and ceruloplasmin (approximately 50% of controls) ferroxidase activity. Liver hepcidin expression was significantly downregulated by copper deficiency (approximately 60% of controls), and enterocyte mRNA and protein levels of ferroportin1 were increased to 2.5 and 10 times, respectively, relative to controls, by copper deficiency, indicating a systemic iron deficiency in the copper-deficient mice. Interestingly, hephaestin protein levels were significantly decreased to approximately 40% of control, suggesting that decreased enterocyte copper content leads to decreased hephaestin synthesis and/or stability. We also examined the effect of copper deficiency on hephaestin in vitro in the HT29 cell line and found dramatically decreased hephaestin synthesis and activity. Both in vivo and in vitro studies indicate that copper is required for the proper processing and/or stability of hephaestin.
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Affiliation(s)
- Huijun Chen
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720-3104, USA
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110
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Merchant SS, Allen MD, Kropat J, Moseley JL, Long JC, Tottey S, Terauchi AM. Between a rock and a hard place: trace element nutrition in Chlamydomonas. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:578-94. [PMID: 16766055 DOI: 10.1016/j.bbamcr.2006.04.007] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2006] [Revised: 04/06/2006] [Accepted: 04/06/2006] [Indexed: 11/23/2022]
Abstract
Photosynthetic organisms are among the earliest life forms on earth and their biochemistry is strictly dependent on a wide range of inorganic nutrients owing to the use of metal cofactor-dependent enzymes in photosynthesis, respiration, inorganic nitrogen and sulfur assimilation. Chlamydomonas reinhardtii is a photosynthetic eukaryotic model organism for the study of trace metal homeostasis. Chlamydomonas spp. are widely distributed and can be found in soil, glaciers, acid mines and sewage ponds, suggesting that the genus has significant capacity for acclimation to micronutrient availability. Analysis of the draft genome indicates that metal homeostasis mechanisms in Chlamydomonas represent a blend of mechanisms operating in animals, plants and microbes. A combination of classical genetics, differential expression and genomic analysis has led to the identification of homologues of components known to operate in fungi and animals (e.g., Fox1, Ftr1, Fre1, Fer1, Ctr1/2) as well as novel molecules involved in copper and iron nutrition (Crr1, Fea1/2). Besides activating iron assimilation pathways, iron-deficient Chlamydomonas cells re-adjust metabolism by reducing light delivery to photosystem I (to avoid photo-oxidative damage resulting from compromised FeS clusters) and by modifying the ferredoxin profile (perhaps to accommodate preferential allocation of reducing equivalents). Up-regulation of a MnSOD isoform may compensate for loss of FeSOD. Ferritin could function to buffer the iron released from programmed degradation of iron-containing enzymes in the chloroplast. Some metabolic adjustments are made in anticipation of deficiency while others occur only with sustained or severe deficiency. Copper-deficient Chlamydomonas cells induce a copper assimilation pathway consisting of a cell surface reductase and a Cu(+) transporter (presumed CTR homologue). There are metabolic adaptations in addition: the synthesis of "back-up" enzymes for plastocyanin in photosynthesis and the ferroxidase in iron assimilation plus activation of alternative oxidase to handle the electron "overflow" resulting from reduced cytochrome oxidase function. Oxygen-dependent enzymes in the tetrapyrrole pathway (coproporphyrinogen oxidase and aerobic oxidative cyclase) are also increased in expression and activity by as much as 10-fold but the connection between copper nutrition and tetrapyrroles is not understood. The copper-deficiency responses are mediated by copper response elements that are defined by a GTAC core sequence and a novel metalloregulator, Crr1, which uses a zinc-dependent SBP domain to bind to the CuRE. The Chlamydomonas model is ideal for future investigation of nutritional manganese deficiency and selenoenzyme function. It is also suited for studies of trace nutrient interactions, nutrition-dependent metabolic changes, the relationship between photo-oxidative stress and metal homeostasis, and the important questions of differential allocation of limiting metal nutrients (e.g., to respiration vs. photosynthesis).
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Affiliation(s)
- Sabeeha S Merchant
- Department of Chemistry and Biochemistry, Box 951569, University of California-Los Angeles, Los Angeles, CA 90095-1569, USA.
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111
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Wilhelm C, Büchel C, Fisahn J, Goss R, Jakob T, Laroche J, Lavaud J, Lohr M, Riebesell U, Stehfest K, Valentin K, Kroth PG. The regulation of carbon and nutrient assimilation in diatoms is significantly different from green algae. Protist 2006; 157:91-124. [PMID: 16621693 DOI: 10.1016/j.protis.2006.02.003] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Christian Wilhelm
- Department of Plant Physiology, Institute of Biology I, University of Leipzig, Johannisallee 23, 04103 Leipzig, Germany.
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112
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Peers G, Price NM. Copper-containing plastocyanin used for electron transport by an oceanic diatom. Nature 2006; 441:341-4. [PMID: 16572122 DOI: 10.1038/nature04630] [Citation(s) in RCA: 168] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2006] [Accepted: 02/07/2006] [Indexed: 11/09/2022]
Abstract
The supply of some essential metals to pelagic ecosystems is less than the demand, so many phytoplankton have slow rates of photosynthetic production and restricted growth. The types and amounts of metals required by phytoplankton depends on their evolutionary history and on their adaptations to metal availability, which varies widely among ocean habitats. Diatoms, for example, need considerably less iron (Fe) to grow than chlorophyll-b-containing taxa, and the oceanic species demand roughly one-tenth the amount of coastal strains. Like Fe, copper (Cu) is scarce in the open sea, but notably higher concentrations of it are required for the growth of oceanic than of coastal isolates. Here we report that the greater Cu requirement in an oceanic diatom, Thalassiosira oceanica, is entirely due to a single Cu-containing protein, plastocyanin, which--until now--was only known to exist in organisms with chlorophyll b and cyanobacteria. Algae containing chlorophyll c, including the closely related coastal species T. weissflogii, are thought to lack plastocyanin and contain a functionally equivalent Fe-containing homologue, cytochrome c6 (ref. 9). Copper deficiency in T. oceanica inhibits electron transport regardless of Fe status, implying a constitutive role for plastocyanin in the light reactions of photosynthesis in this species. The results suggest that selection pressure imposed by Fe limitation has resulted in the use of a Cu protein for photosynthesis in an oceanic diatom. This biochemical switch reduces the need for Fe and increases the requirement for Cu, which is relatively more abundant in the open sea.
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Affiliation(s)
- Graham Peers
- Department of Biology, McGill University, 1205 Avenue Dr Penfield, Montreal, Quebec H3A 1B1, Canada.
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113
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Kwok EY, Stoj CS, Severance S, Kosman DJ. An engineered bifunctional high affinity iron uptake protein in the yeast plasma membrane. J Inorg Biochem 2006; 100:1053-60. [PMID: 16387364 DOI: 10.1016/j.jinorgbio.2005.11.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2005] [Revised: 10/28/2005] [Accepted: 11/15/2005] [Indexed: 11/19/2022]
Abstract
High affinity iron uptake in fungi is supported by a plasma membrane protein complex that includes a multicopper ferroxidase enzyme and a ferric iron permease. In Saccharomyces cerevisiae, this complex is composed of the ferroxidase Fet3p and the permease Ftr1p. Fe(II) serves as substrate for Fe-uptake by being substrate for Fet3p; the resulting Fet3p-produced Fe(III) is then transported across the membrane via Ftr1p. A model of metabolite channeling of this Fe(III) is tested here by first constructing and kinetically characterizing in Fe-uptake two Fet3p-Ftr1p chimeras in which the multicopper oxidase/ferroxidase domain of Fet3p has been fused to the Ftr1p iron permease. Although the bifunctional chimeras are as kinetically efficient in Fe-uptake as is the wild type two-component system, they lack the adaptability and fidelity in Fe-uptake of the wild type. Specifically, Fe-uptake through the Fet3p, Ftr1p complex is insensitive to a potential Fe(III) trapping agent - citrate - whereas Fe-uptake via the chimeric proteins is competitively inhibited by this Fe(III) chelator. This inhibition does not appear to be due to scavenging Fet3p-produced Fe(III) that is in equilibrium with bulk solvent but could be due to leakiness to citrate found in the bifunctional but not the two-component system. The data are consistent with a channeling model of Fe-trafficking in the Fet3p, Ftr1p complex and suggest that in this system, Fet3p serves as a redox sieve that presents Fe(III) specifically for permeation through Ftr1p.
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Affiliation(s)
- E Y Kwok
- Department of Biochemistry, The University at Buffalo, 140 Farber Hall, Buffalo, NY 14214, USA
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114
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Debut AJ, Dumay QC, Barabote RD, Saier MH. The Iron/Lead Transporter Superfamily of Fe 3+/Pb 2+ Uptake Systems. J Mol Microbiol Biotechnol 2006; 11:1-9. [PMID: 16825785 DOI: 10.1159/000092814] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Oxidase-dependent ferrous iron uptake transporters of the OFeT family and lead uptake transporters of the PbrT family comprise the iron/lead transporter (ILT) superfamily (transporter classification No. 9.A.10). All sequenced homologues of the ILT superfamily were multiply aligned, and conserved motifs, including fully conserved acidic residues in putative transmembrane segments (TMSs) 1 and 4, previously implicated in heavy metal binding, were identified. Topological analyses confirmed the presence of 7 conserved TMSs in a 3 + 3 + 1 arrangement where the two 3 TMS elements are internally repeated. Phylogenetic analyses revealed the presence of several sequence divergent clusters of orthologous proteins that group roughly according to the phylogenes of the organisms of origin. The results serve to characterize and provide evolutionary insight into a novel superfamily of heavy metal uptake transporters.
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Affiliation(s)
- Aurore J Debut
- Division of Biological Sciences, University of California at San Diego, La Jolla 92093-0116, USA
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115
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Eberhard S, Jain M, Im CS, Pollock S, Shrager J, Lin Y, Peek AS, Grossman AR. Generation of an oligonucleotide array for analysis of gene expression in Chlamydomonas reinhardtii. Curr Genet 2005; 49:106-24. [PMID: 16333659 DOI: 10.1007/s00294-005-0041-2] [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: 10/03/2005] [Revised: 10/24/2005] [Accepted: 10/25/2005] [Indexed: 01/08/2023]
Abstract
The availability of genome sequences makes it possible to develop microarrays that can be used for profiling gene expression over developmental time, as organisms respond to environmental challenges, and for comparison between wild-type and mutant strains under various conditions. The desired characteristics of microarrays (intense signals, hybridization specificity and extensive coverage of the transcriptome) were not fully met by the previous Chlamydomonas reinhardtii microarray: probes derived from cDNA sequences (approximately 300 bp) were prone to some nonspecific cross-hybridization and coverage of the transcriptome was only approximately 20%. The near completion of the C. reinhardtii nuclear genome sequence and the availability of extensive cDNA information have made it feasible to improve upon these aspects. After developing a protocol for selecting a high-quality unigene set representing all known expressed sequences, oligonucleotides were designed and a microarray with approximately 10,000 unique array elements (approximately 70 bp) covering 87% of the known transcriptome was developed. This microarray will enable researchers to generate a global view of gene expression in C. reinhardtii. Furthermore, the detailed description of the protocol for selecting a unigene set and the design of oligonucleotides may be of interest for laboratories interested in developing microarrays for organisms whose genome sequences are not yet completed (but are nearing completion).
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Affiliation(s)
- Stephan Eberhard
- Department of Plant Biology, The Carnegie Institution, 260 Panama Street, Stanford, CA, 94305, USA.
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116
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Abdel-Ghany SE, Müller-Moulé P, Niyogi KK, Pilon M, Shikanai T. Two P-type ATPases are required for copper delivery in Arabidopsis thaliana chloroplasts. THE PLANT CELL 2005; 17:1233-51. [PMID: 15772282 PMCID: PMC1087999 DOI: 10.1105/tpc.104.030452] [Citation(s) in RCA: 229] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Accepted: 02/18/2005] [Indexed: 05/20/2023]
Abstract
Copper delivery to the thylakoid lumen protein plastocyanin and the stromal enzyme Cu/Zn superoxide dismutase in chloroplasts is required for photosynthesis and oxidative stress protection. The copper delivery system in chloroplasts was characterized by analyzing the function of copper transporter genes in Arabidopsis thaliana. Two mutant alleles were identified of a previously uncharacterized gene, PAA2 (for P-type ATPase of Arabidopsis), which is required for efficient photosynthetic electron transport. PAA2 encodes a copper-transporting P-type ATPase with sequence similarity to PAA1, which functions in copper transport in chloroplasts. Both proteins localized to the chloroplast, as indicated by fusions to green fluorescent protein. The PAA1 fusions were found in the chloroplast periphery, whereas PAA2 fusions were localized in thylakoid membranes. The phenotypes of paa1 and paa2 mutants indicated that the two transporters have distinct functions: whereas both transporters are required for copper delivery to plastocyanin, copper delivery to the stroma is inhibited only in paa1 but not in paa2. The effects of paa1 and paa2 on superoxide dismutase isoform expression levels suggest that stromal copper levels regulate expression of the nuclear genes IRON SUPEROXIDE DISMUTASE1 and COPPER/ZINC SUPEROXIDE DISMUTASE2. A paa1 paa2 double mutant was seedling-lethal, underscoring the importance of copper to photosynthesis. We propose that PAA1 and PAA2 function sequentially in copper transport over the envelope and thylakoid membrane, respectively.
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Affiliation(s)
- Salah E Abdel-Ghany
- Biology Department, Colorado State University, Fort Collins, Colorado 80523, USA
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117
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Eriksson M, Moseley JL, Tottey S, Del Campo JA, Quinn J, Kim Y, Merchant S. Genetic dissection of nutritional copper signaling in chlamydomonas distinguishes regulatory and target genes. Genetics 2005; 168:795-807. [PMID: 15514054 PMCID: PMC1448816 DOI: 10.1534/genetics.104.030460] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
A genetic screen for Chlamydomonas reinhardtii mutants with copper-dependent growth or nonphotosynthetic phenotypes revealed three loci, COPPER RESPONSE REGULATOR 1 (CRR1), COPPER RESPONSE DEFECT 1 (CRD1), and COPPER RESPONSE DEFECT 2 (CRD2), distinguished as regulatory or target genes on the basis of phenotype. CRR1 was shown previously to be required for transcriptional activation of target genes like CYC6, CPX1, and CRD1, encoding, respectively, cytochrome c(6) (which is a heme-containing substitute for copper-containing plastocyanin), coproporphyrinogen III oxidase, and Mg-protoporphyrin IX monomethylester cyclase. We show here that CRR1 is required also for normal accumulation of copper proteins like plastocyanin and ferroxidase in copper-replete medium and for apoplastocyanin degradation in copper-deficient medium, indicating that a single pathway controls nutritional copper homeostasis at multiple levels. CRR1 is linked to the SUPPRESSOR OF PCY1-AC208 13 (SOP13) locus, which corresponds to a gain-of-function mutation resulting in copper-independent expression of CYC6. CRR1 is required also for hypoxic growth, pointing to a physiologically meaningful regulatory connection between copper deficiency and hypoxia. The growth phenotype of crr1 strains results primarily from secondary iron deficiency owing to reduced ferroxidase abundance, suggesting a role for CRR1 in copper distribution to a multicopper ferroxidase involved in iron assimilation. Mutations at the CRD2 locus also result in copper-conditional iron deficiency, which is consistent with a function for CRD2 in a pathway for copper delivery to the ferroxidase. Taken together, the observations argue for a specialized copper-deficiency adaptation for iron uptake in Chlamydomonas.
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Affiliation(s)
- Mats Eriksson
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California, 90095-1569, USA
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118
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Affiliation(s)
- Arthur R Grossman
- The Carnegie Institution, Department of Plant Biology, Stanford, California 94305, USA.
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119
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Hanikenne M, Krämer U, Demoulin V, Baurain D. A comparative inventory of metal transporters in the green alga Chlamydomonas reinhardtii and the red alga Cyanidioschizon merolae. PLANT PHYSIOLOGY 2005; 137:428-46. [PMID: 15710683 PMCID: PMC1065346 DOI: 10.1104/pp.104.054189] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2004] [Revised: 11/16/2004] [Accepted: 11/18/2004] [Indexed: 05/20/2023]
Affiliation(s)
- Marc Hanikenne
- Metal Homeostasis Group, Max Planck Institute for Plant Molecular Physiology, 14476 Golm, Germany.
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120
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Rosakis A, Köster W. Divalent metal transport in the green microalga Chlamydomonas reinhardtii is mediated by a protein similar to prokaryotic Nramp homologues. Biometals 2005; 18:107-20. [PMID: 15865416 DOI: 10.1007/s10534-004-2481-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Information about the molecular mechanisms of metal transport in algae is scarce, despite the significant status these organisms have in aquatic ecosystems. In the present study, we describe the cloning and functional characterization of a divalent metal transporter (named DMT1) in the green microalga Chlamydomonas reinhardtii Dangeard. The longest open reading frame of the cloned DMT1 cDNA encodes a protein of 513 amino acids with 11 putative transmembrane domains. The protein belongs to the Nramp family of divalent metal transporters and shows surprisingly higher similarity to some prokaryotic than to eukaryotic polypeptides. Especially the N-terminus, which is longer than of every other homologue considered in this study, displays--uniquely among selected eukaryotic Nramps--exclusively prokaryotic characteristics. Functional complementation experiments in yeast strains with impaired metal transport systems, revealed that C. reinhardtii DMT1 has a broad specificity, acting in the transport of several divalent metals (manganese, iron, cadmium, copper), but excluding zinc.
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Affiliation(s)
- Alexandra Rosakis
- Environmental Microbiology and Molecular Ecotoxicology, Swiss Federal Institute for Environmental Science and Technology (EAWAG), Uberlandstrasse 133, CH-8600 Duebendorf, Switzerland
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121
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Kwok E, Kosman D. Iron in yeast: Mechanisms involved in homeostasis. TOPICS IN CURRENT GENETICS 2005. [DOI: 10.1007/4735_92] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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122
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Rutherford JC, Bird AJ. Metal-responsive transcription factors that regulate iron, zinc, and copper homeostasis in eukaryotic cells. EUKARYOTIC CELL 2004; 3:1-13. [PMID: 14871932 PMCID: PMC329510 DOI: 10.1128/ec.3.1.1-13.2004] [Citation(s) in RCA: 200] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Julian C Rutherford
- Division of Hematology, Department of Internal Medicine, University of Utah Health Sciences Center, Salt Lake City, Utah 84132, USA
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123
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Quinn JM, Kropat J, Merchant S. Copper response element and Crr1-dependent Ni(2+)-responsive promoter for induced, reversible gene expression in Chlamydomonas reinhardtii. EUKARYOTIC CELL 2004; 2:995-1002. [PMID: 14555481 PMCID: PMC219375 DOI: 10.1128/ec.2.5.995-1002.2003] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Cpx1 and Cyc6 genes of Chlamydomonas reinhardtii are activated in copper-deficient cells via a signal transduction pathway that requires copper response elements (CuREs) and a copper response regulator defined by the CRR1 locus. The two genes can also be activated by provision of nickel or cobalt ions in the medium. The response to nickel ions requires at least one CuRE and also CRR1 function, suggesting that nickel interferes with a component in the nutritional copper signal transduction pathway. Nickel does not act by preventing copper uptake/utilization because (i) holoplastocyanin formation is unaffected in Ni(2+)-treated cells and (ii) provision of excess copper cannot reverse the Ni-dependent activation of the target genes. The CuRE is sufficient for conferring Ni-responsive expression to a reporter gene, which suggests that the system has practical application as a vehicle for inducible gene expression. The inducer can be removed either by replacing the medium or by chelating the inducer with excess EDTA, either of which treatments reverses the activation of the target genes.
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Affiliation(s)
- Jeanette M Quinn
- Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, California 90095-1569, USA
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124
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Del Campo JA, Quinn JM, Merchant S. Evaluation of oxygen response involving differential gene expression in Chlamydomonas reinhardtii. Methods Enzymol 2004; 381:604-17. [PMID: 15063701 DOI: 10.1016/s0076-6879(04)81039-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
Affiliation(s)
- José A Del Campo
- Department of Chemistry and Biochemistry, Los Angeles, California 90095-1569, USA
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125
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Rosakis A, Köster W. Transition metal transport in the green microalga Chlamydomonas reinhardtii—genomic sequence analysis. Res Microbiol 2004; 155:201-10. [PMID: 15059633 DOI: 10.1016/j.resmic.2003.12.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2003] [Accepted: 12/16/2003] [Indexed: 11/21/2022]
Abstract
Uptake and export systems play a major role in transition metal homeostasis. The objective of this study was to identify potential metal transport mechanisms in the green microalga Chlamydomonas reinhardtii. We concentrated on the four major transition metal transporter families found in plants and other organisms: the ZIP, CDF and Nramp families, and the CPx-ATPases. Using the information available for these protein families we performed comparative sequence analysis in the recently released genome of C. reinhardtii. Using this approach we were able to identify members of all four transporter families (four ZIPs, one CDF, two CPx-ATPases, and five Nramps). These findings advance our current knowledge of the metal transport processes present in C. reinhardtii. In addition, by subsequent in silico splicing of the genomic sequence we obtained cDNA sequences which led to the identification of ESTs (expressed sequence tags) in the C. reinhardtii EST database. These identified ESTs will be valuable for the cloning and characterization of several metal transporters utilized by the alga.
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Affiliation(s)
- Alexandra Rosakis
- Environmental Microbiology and Molecular Ecotoxicology, Swiss Federal Institute for Environmental Science and Technology (EAWAG), Ueberlandstrasse 133, 8600 Duebendorf, Switzerland
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126
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Hoopes JT, Dean JF. Ferroxidase activity in a laccase-like multicopper oxidase from Liriodendron tulipifera. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2004; 42:27-33. [PMID: 15061081 DOI: 10.1016/j.plaphy.2003.10.011] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Ferroxidase activity was detected in a laccase-like multicopper oxidase (LMCO) produced in transgenic tobacco cells expressing an LMCO cDNA (Ltlacc2.2) cloned from yellow-poplar (Liriodendron tulipifera). This marks the first report of ferroxidase activity associated with a plant laccase and suggests that some members of this plant enzyme family may have physiological functions based on activities other than their more widely recognized phenoloxidase activity. Recent work with LMCOs from bacteria, yeast and mammals has shown that metal oxidase activities in these enzymes can be important for their primary physiological functions, With respect to ferroxidase activity in certain plant LMCOs, it is proposed that the high levels of LMCO expression in plant vascular tissues may reflect the need for high-efficiency iron uptake pumps in tissues that undergo lignification during normal development. Such iron uptake pumps would function to minimize levels of free iron so that reactive oxygen species do not reach toxic levels when H2O2 is generated for peroxidase-mediated monolignol coupling during lignin deposition.
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Affiliation(s)
- James Todd Hoopes
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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127
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Koukal B, Guéguen C, Pardos M, Dominik J. Influence of humic substances on the toxic effects of cadmium and zinc to the green alga Pseudokirchneriella subcapitata. CHEMOSPHERE 2003; 53:953-961. [PMID: 14505718 DOI: 10.1016/s0045-6535(03)00720-3] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A method combining (1 h) algal photosynthesis inhibition tests and tangential-flow ultrafiltration (TFF) technique (cut-off 1 kDa) was used to determine the effect of humic substances (HS) on acute metal toxicity to Pseudokirchneriella subcapitata. Three "standard" HS (soil and peat humic acids and Suwannee River fulvic acids) at two concentrations (1 and 5 mg/l) and two metals (Zn at 390 microg/l and Cd at 200 microg/l) were studied. Toxicity of Cd and Zn to P. subcapitata was significantly (p<0.05) reduced in the presence of humic acids (HA) but not in the presence of Suwannee River fulvic acids (SRFA). Metal partitioning between colloidal (1 microm-1 kDa) and truly dissolved (<1 kDa) fractions was found to match a decrease of metal toxicity in the presence of HA, but not in the presence of SRFA. The results suggested that HA reduced Cd and Zn toxicity in two different ways: (1) HA decrease the amount of free metal ions. Metal-HA complexes are high molecular weight, relatively stable with regard to metal-exchange reactions and consequently the metals were less bioavailable. (2) HA adsorbed onto algal surfaces, shielded the cells from free Cd and Zn ions. Several possible explanations can be postulated to account for the observed SRFA results: (1) Cd- and Zn-SRFA complexes are thought to be labile (i.e. undergo rapid dissociation); (2) SRFA coagulated, presumably during equilibration, and that coagulation altered metal complexing behavior of SRFA; (3) FA has a lower ability to adsorb on cell membranes at pH>7.
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Affiliation(s)
- Brahim Koukal
- Universite of Geneve, Institut F.-A. Forel, 10 route de Suisse, CH-1290 Versoix, Switzerland.
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128
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Wintz H, Fox T, Wu YY, Feng V, Chen W, Chang HS, Zhu T, Vulpe C. Expression profiles of Arabidopsis thaliana in mineral deficiencies reveal novel transporters involved in metal homeostasis. J Biol Chem 2003; 278:47644-53. [PMID: 13129917 DOI: 10.1074/jbc.m309338200] [Citation(s) in RCA: 235] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Plants directly assimilate minerals from the environment and thus are key for acquisition of metals by all subsequent consumers. Limited bio-availability of copper, zinc and iron in soil decreases both the agronomic productivity and the nutrient quality of crops. Understanding the molecular mechanisms underlying metal homeostasis in plants is a prerequisite to optimizing plant yield and metal nutrient content. To absorb and maintain a balance of potentially toxic metal ions, plants utilize poorly understood mechanisms involving a large number of membrane transporters and metal binding proteins with overlapping substrate specificities and complex regulation. To better understand the function and the integrated regulation, we analyzed in Arabidopsis the expression patterns in roots and in leaves of 53 genes coding for known or potential metal transporters, in response to copper, zinc, and iron deficiencies in Arabidopsis. Comparative analysis of gene expression profiles revealed specific transcriptional regulation by metals of the genes contrasting with the known wide substrate specificities of the encoded transporters. Our analysis suggested novel transport roles for several gene products and we used functional complementation of yeast mutants to correlate specific regulation by metals with transport activity. We demonstrate that two ZIP genes, ZIP2 and ZIP4, are involved in copper transport. We also present evidence that AtOPT3, a member of the oligopeptide transporter gene family with significant similarities to the maize iron-phytosiderophore transporter YS1, is regulated by metals and heterologous expression AtOPT3 can rescue yeast mutants deficient in metal transport.
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Affiliation(s)
- Henri Wintz
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, California 94720, USA.
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129
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Stoj C, Kosman DJ. Cuprous oxidase activity of yeast Fet3p and human ceruloplasmin: implication for function. FEBS Lett 2003; 554:422-6. [PMID: 14623105 DOI: 10.1016/s0014-5793(03)01218-3] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Fet3 protein in Saccharomyces cerevisiae and mammalian ceruloplasmin are multicopper oxidases (MCO) that are required for iron homeostasis via their catalysis of the ferroxidase reaction, 4Fe(2+)+O(2)+4H(+)-->4Fe(3+)+2H(2)O. The enzymes may play an essential role in copper homeostasis since they exhibit a strikingly similar kinetic activity towards Cu(1+) as substrate. In contrast, laccase, an MCO that exhibits weak activity towards Fe(2+), exhibits a similarly weak activity towards Cu(1+). Kinetic analyses of the Fet3p reaction demonstrate that the ferroxidase and cuprous oxidase activities are due to the same electron transfer site on the enzyme. These two ferroxidases are fully competent kinetically to play a major role in maintaining the cuprous-cupric redox balance in aerobic organisms.
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Affiliation(s)
- Christopher Stoj
- Department of Biochemistry, School of Medicine and Biomedical Sciences, State University of New York, 140 Farber Hall, 3435 Main St., Buffalo, NY 14214, USA
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130
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Hanikenne M. Chlamydomonas reinhardtii as a eukaryotic photosynthetic model for studies of heavy metal homeostasis and tolerance. THE NEW PHYTOLOGIST 2003; 159:331-340. [PMID: 33873346 DOI: 10.1046/j.1469-8137.2003.00788.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The green alga Chlamydomonas reinhardtii is a useful model of a photosynthetic cell. This unicellular eukaryote has been intensively used for studies of a number of physiological processes such as photosynthesis, respiration, nitrogen assimilation, flagella motility and basal body function. Its easy-to-manipulate and short life cycle make this organism a powerful tool for genetic analysis. Over the past 15 yr, a dramatically increased number of molecular technologies (including nuclear and organellar transformation systems, cosmid, yeast artificial chromosome (YAC) and bacterial artificial chromosome (BAC) libraries, reporter genes, RNA interference, DNA microarrays, etc.) have been applied to Chlamydomonas. Moreover, as parts of the Chlamydomonas genome project, molecular mapping, as well as whole genome and extended expressed sequence tag (EST) sequencing programs, are currently underway. These developments have allowed Chlamydomonas to become an extremely valuable model for molecular approaches to heavy metal homeostasis and tolerance in photosynthetic organisms.
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Affiliation(s)
- M Hanikenne
- Genetics of Microorganisms, Department of Life Sciences, B22, University of Liège, B4000 Liège, Belgium
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131
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Moseley JL, Allinger T, Herzog S, Hoerth P, Wehinger E, Merchant S, Hippler M. Adaptation to Fe-deficiency requires remodeling of the photosynthetic apparatus. EMBO J 2002; 21:6709-20. [PMID: 12485992 PMCID: PMC139087 DOI: 10.1093/emboj/cdf666] [Citation(s) in RCA: 215] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The molecular mechanisms underlying the onset of Fe-deficiency chlorosis and the maintenance of photosynthetic function in chlorotic chloroplasts are relevant to global photosynthetic productivity. We describe a series of graded responses of the photosynthetic apparatus to Fe-deficiency, including a novel response that occurs prior to the onset of chlorosis, namely the disconnection of the LHCI antenna from photosystem I (PSI). We propose that disconnection is mediated by a change in the physical properties of PSI-K in PSI in response to a change in plastid Fe content, which is sensed through the occupancy, and hence activity, of the Fe-containing active site in Crd1. We show further that progression of the response involves remodeling of the antenna complexes-specific degradation of existing proteins coupled to the synthesis of new ones, and establishment of a new steady state with decreased stoichiometry of electron transfer complexes. We suggest that these responses are typical of a dynamic photosynthetic apparatus where photosynthetic function is optimized and photooxidative damage is minimized in graduated responses to a combination of nutrients, light quantity and quality.
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Affiliation(s)
| | - Tanja Allinger
- Department of Chemistry and Biochemistry and Molecular Biology Institute, UCLA, 607 Charles E. Young Drive East, Los Angeles, CA 90095-1569, USA,
Lehrstuhl für Pflanzenphysiologie, Friedrich-Schiller-Universität Jena, Dornburger Strasse 159, D-07743 Jena and Lehrstuhl für Biochemie der Pflanzen, Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany Corresponding authors e-mail: or
J.L.Moseley and T.Allinger contributed equally to this work
| | - Sebastian Herzog
- Department of Chemistry and Biochemistry and Molecular Biology Institute, UCLA, 607 Charles E. Young Drive East, Los Angeles, CA 90095-1569, USA,
Lehrstuhl für Pflanzenphysiologie, Friedrich-Schiller-Universität Jena, Dornburger Strasse 159, D-07743 Jena and Lehrstuhl für Biochemie der Pflanzen, Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany Corresponding authors e-mail: or
J.L.Moseley and T.Allinger contributed equally to this work
| | - Patric Hoerth
- Department of Chemistry and Biochemistry and Molecular Biology Institute, UCLA, 607 Charles E. Young Drive East, Los Angeles, CA 90095-1569, USA,
Lehrstuhl für Pflanzenphysiologie, Friedrich-Schiller-Universität Jena, Dornburger Strasse 159, D-07743 Jena and Lehrstuhl für Biochemie der Pflanzen, Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany Corresponding authors e-mail: or
J.L.Moseley and T.Allinger contributed equally to this work
| | | | - Sabeeha Merchant
- Department of Chemistry and Biochemistry and Molecular Biology Institute, UCLA, 607 Charles E. Young Drive East, Los Angeles, CA 90095-1569, USA,
Lehrstuhl für Pflanzenphysiologie, Friedrich-Schiller-Universität Jena, Dornburger Strasse 159, D-07743 Jena and Lehrstuhl für Biochemie der Pflanzen, Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany Corresponding authors e-mail: or
J.L.Moseley and T.Allinger contributed equally to this work
| | - Michael Hippler
- Department of Chemistry and Biochemistry and Molecular Biology Institute, UCLA, 607 Charles E. Young Drive East, Los Angeles, CA 90095-1569, USA,
Lehrstuhl für Pflanzenphysiologie, Friedrich-Schiller-Universität Jena, Dornburger Strasse 159, D-07743 Jena and Lehrstuhl für Biochemie der Pflanzen, Institut für Biologie II, Universität Freiburg, Schänzlestrasse 1, D-79104 Freiburg, Germany Corresponding authors e-mail: or
J.L.Moseley and T.Allinger contributed equally to this work
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