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Divol F, Couch D, Conéjéro G, Roschzttardtz H, Mari S, Curie C. The Arabidopsis YELLOW STRIPE LIKE4 and 6 transporters control iron release from the chloroplast. THE PLANT CELL 2013; 25:1040-1055. [PMID: 23512854 DOI: 10.1105/tpc112107672] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
In most plant cell types, the chloroplast represents the largest sink for iron, which is both essential for chloroplast metabolism and prone to cause oxidative damage. Here, we show that to buffer the potentially harmful effects of iron, besides ferritins for storage, the chloroplast is equipped with specific iron transporters that respond to iron toxicity by removing iron from the chloroplast. We describe two transporters of the YELLOW STRIPE1-LIKE family from Arabidopsis thaliana, YSL4 and YSL6, which are likely to fulfill this function. Knocking out both YSL4 and YSL6 greatly reduces the plant's ability to cope with excess iron. Biochemical and immunolocalization analyses showed that YSL6 resides in the chloroplast envelope. Elemental analysis and histochemical staining indicate that iron is trapped in the chloroplasts of the ysl4 ysl6 double mutants, which also accumulate ferritins. Also, vacuolar iron remobilization and NRAMP3/4 expression are inhibited. Furthermore, ubiquitous expression of YSL4 or YSL6 dramatically reduces plant tolerance to iron deficiency and decreases chloroplastic iron content. These data demonstrate a fundamental role for YSL4 and YSL6 in managing chloroplastic iron. YSL4 and YSL6 expression patterns support their physiological role in detoxifying iron during plastid dedifferentiation occurring in embryogenesis and senescence.
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Affiliation(s)
- Fanchon Divol
- Biochimie et Physiologie Moléculaire des Plantes, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5004/Institut National de la Recherche Agronomique/SupAgro/Université Montpellier 1, F-34060 Montpellier cedex 2, France
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102
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Divol F, Couch D, Conéjéro G, Roschzttardtz H, Mari S, Curie C. The Arabidopsis YELLOW STRIPE LIKE4 and 6 transporters control iron release from the chloroplast. THE PLANT CELL 2013; 25:1040-55. [PMID: 23512854 PMCID: PMC3634676 DOI: 10.1105/tpc.112.107672] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 02/20/2013] [Accepted: 02/26/2013] [Indexed: 05/18/2023]
Abstract
In most plant cell types, the chloroplast represents the largest sink for iron, which is both essential for chloroplast metabolism and prone to cause oxidative damage. Here, we show that to buffer the potentially harmful effects of iron, besides ferritins for storage, the chloroplast is equipped with specific iron transporters that respond to iron toxicity by removing iron from the chloroplast. We describe two transporters of the YELLOW STRIPE1-LIKE family from Arabidopsis thaliana, YSL4 and YSL6, which are likely to fulfill this function. Knocking out both YSL4 and YSL6 greatly reduces the plant's ability to cope with excess iron. Biochemical and immunolocalization analyses showed that YSL6 resides in the chloroplast envelope. Elemental analysis and histochemical staining indicate that iron is trapped in the chloroplasts of the ysl4 ysl6 double mutants, which also accumulate ferritins. Also, vacuolar iron remobilization and NRAMP3/4 expression are inhibited. Furthermore, ubiquitous expression of YSL4 or YSL6 dramatically reduces plant tolerance to iron deficiency and decreases chloroplastic iron content. These data demonstrate a fundamental role for YSL4 and YSL6 in managing chloroplastic iron. YSL4 and YSL6 expression patterns support their physiological role in detoxifying iron during plastid dedifferentiation occurring in embryogenesis and senescence.
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103
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Forieri I, Wirtz M, Hell R. Toward new perspectives on the interaction of iron and sulfur metabolism in plants. FRONTIERS IN PLANT SCIENCE 2013; 4:357. [PMID: 24106494 PMCID: PMC3788360 DOI: 10.3389/fpls.2013.00357] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Accepted: 08/23/2013] [Indexed: 05/18/2023]
Abstract
The deficiency of nutrients has been extensively investigated because of its impact on plant growth and yield. So far, the effects of a combined nutrient limitation have rarely been analyzed, although such situations are likely to occur in agroecosystems. Iron (Fe) is a prerequisite for many essential cellular functions. Its availability is easily becoming limiting for plant growth and thus higher plants have evolved different strategies to cope with Fe deficiency. Sulfur (S) is an essential macro-nutrient and the responses triggered by shortage situations have been well characterized. The interaction between these two nutrients is less investigated but might be of particular importance because most of the metabolically active Fe is bound to S in Fe-S clusters. The biosynthesis of Fe-S clusters requires the provision of reduced S and chelated Fe in a defined stoichiometric ratio, strongly suggesting coordination between the metabolisms of the two nutrients. Here the available information on interactions between Fe and S nutritional status is evaluated. Experiments with Arabidopsis thaliana and crop plants indicate a co-regulation and point to a possible role of Fe-S cluster synthesis or abundance in the Fe/S network.
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Affiliation(s)
- Ilaria Forieri
- Department of Molecular Biology of Plants, Centre for Organismal Studies Heidelberg, University of HeidelbergHeidelberg, Germany
- The Hartmut Hoffmann-Berling International Graduate School of Molecular and Cellular Biology, University of HeidelbergHeidelberg, Germany
| | - Markus Wirtz
- Department of Molecular Biology of Plants, Centre for Organismal Studies Heidelberg, University of HeidelbergHeidelberg, Germany
| | - Rüdiger Hell
- Department of Molecular Biology of Plants, Centre for Organismal Studies Heidelberg, University of HeidelbergHeidelberg, Germany
- *Correspondence: Rüdiger Hell, Department of Molecular Biology of Plants, Centre for Organismal Studies Heidelberg, University of Heidelberg, Im Neuenheimer Feld 360, 69120 Heidelberg, Germany e-mail:
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104
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Iron-sulphur clusters, their biosynthesis, and biological functions in protozoan parasites. ADVANCES IN PARASITOLOGY 2013; 83:1-92. [PMID: 23876871 DOI: 10.1016/b978-0-12-407705-8.00001-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Fe-S clusters are ensembles of sulphide-linked di-, tri-, and tetra-iron centres of a variety of metalloproteins that play important roles in reduction and oxidation of mitochondrial electron transport, energy metabolism, regulation of gene expression, cell survival, nitrogen fixation, and numerous other metabolic pathways. The Fe-S clusters are assembled by one of four distinct systems: NIF, SUF, ISC, and CIA machineries. The ISC machinery is a house-keeping system conserved widely from prokaryotes to higher eukaryotes, while the other systems are present in a limited range of organisms and play supplementary roles under certain conditions such as stress. Fe-S cluster-containing proteins and the components required for Fe-S cluster biosynthesis are modulated under stress conditions, drug resistance, and developmental stages. It is also known that a defect in Fe-S proteins and Fe-S cluster biogenesis leads to many genetic disorders in humans, which indicates the importance of the systems. In this review, we describe the biological and physiological significance of Fe-S cluster-containing proteins and their biosynthesis in parasitic protozoa including Plasmodium, Trypanosoma, Leishmania, Giardia, Trichomonas, Entamoeba, Cryptosporidium, Blastocystis, and microsporidia. We also discuss the roles of Fe-S cluster biosynthesis in proliferation, differentiation, and stress response in protozoan parasites. The heterogeneity of the systems and the compartmentalization of Fe-S cluster biogenesis in the protozoan parasites likely reflect divergent evolution under highly diverse environmental niches, and influence their parasitic lifestyle and pathogenesis. Finally, both Fe-S cluster-containing proteins and their biosynthetic machinery in protozoan parasites are remarkably different from those in their mammalian hosts. Thus, they represent a rational target for the development of novel chemotherapeutic and prophylactic agents against protozoan infections.
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105
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Mackiewicz P, Bodył A, Gagat P. Protein import into the photosynthetic organelles of Paulinella chromatophora and its implications for primary plastid endosymbiosis. Symbiosis 2012; 58:99-107. [PMID: 23482692 PMCID: PMC3589627 DOI: 10.1007/s13199-012-0202-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Accepted: 11/20/2012] [Indexed: 10/27/2022]
Abstract
The rhizarian amoeba Paulinella chromatophora harbors two photosynthetically active organelles of cyanobacterial origin that have been acquired independently of classic primary plastids. Because their acquisition did take place relatively recently, they are expected to provide new insight into the ancient cyanobacterial primary endosymbiosis. During the process of Paulinella endosymbiont-to-organelle transformation, more than 30 genes have been transferred from the organelle to the host nuclear genome via endosymbiotic gene transfer (EGT). The article discusses step-by-step protein import of EGT-derived proteins into Paulinella photosynthetic organelles with the emphasis on the nature of their targeting signals and the final passage of proteins through the inner organelle membrane. The latter most probably involves a simplified Tic translocon composed of Tic21- and Tic32-like proteins as well as a Hsp70-based motor responsible for pulling of imported proteins into the organelle matrix. Our results indicate that although protein translocation across the inner membrane of Paulinella photosynthetic organelles seems to resemble the one in classic primary plastids, the transport through the outer membrane does not. The differences could result from distinct integration pathways of Paulinella photosynthetic organelles and primary plastids with their respective host cells.
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Affiliation(s)
- Paweł Mackiewicz
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Przybyszewskiego 63/77, 51-148 Wrocław, Poland
| | - Andrzej Bodył
- Laboratory of Evolutionary Protistology, Division of Invertebrate Biology, Evolution and Conservation, Faculty of Biological Sciences, University of Wrocław, ul. Przybyszewskiego 63/77, 51-148 Wrocław, Poland
| | - Przemysław Gagat
- Department of Genomics, Faculty of Biotechnology, University of Wrocław, ul. Przybyszewskiego 63/77, 51-148 Wrocław, Poland
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106
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Shi LX, Theg SM. The chloroplast protein import system: from algae to trees. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:314-31. [PMID: 23063942 DOI: 10.1016/j.bbamcr.2012.10.002] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Revised: 09/07/2012] [Accepted: 10/01/2012] [Indexed: 01/15/2023]
Abstract
Chloroplasts are essential organelles in the cells of plants and algae. The functions of these specialized plastids are largely dependent on the ~3000 proteins residing in the organelle. Although chloroplasts are capable of a limited amount of semiautonomous protein synthesis - their genomes encode ~100 proteins - they must import more than 95% of their proteins after synthesis in the cytosol. Imported proteins generally possess an N-terminal extension termed a transit peptide. The importing translocons are made up of two complexes in the outer and inner envelope membranes, the so-called Toc and Tic machineries, respectively. The Toc complex contains two precursor receptors, Toc159 and Toc34, a protein channel, Toc75, and a peripheral component, Toc64/OEP64. The Tic complex consists of as many as eight components, namely Tic22, Tic110, Tic40, Tic20, Tic21 Tic62, Tic55 and Tic32. This general Toc/Tic import pathway, worked out largely in pea chloroplasts, appears to operate in chloroplasts in all green plants, albeit with significant modifications. Sub-complexes of the Toc and Tic machineries are proposed to exist to satisfy different substrate-, tissue-, cell- and developmental requirements. In this review, we summarize our understanding of the functions of Toc and Tic components, comparing these components of the import machinery in green algae through trees. We emphasize recent findings that point to growing complexities of chloroplast protein import process, and use the evolutionary relationships between proteins of different species in an attempt to define the essential core translocon components and those more likely to be responsible for regulation. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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Affiliation(s)
- Lan-Xin Shi
- Department of Plant Biology, University of California-Davis, One Shields Avenue, Davis, CA 95616, USA.
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107
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Blaby-Haas CE, Merchant SS. The ins and outs of algal metal transport. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1823:1531-52. [PMID: 22569643 PMCID: PMC3408858 DOI: 10.1016/j.bbamcr.2012.04.010] [Citation(s) in RCA: 126] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 04/20/2012] [Accepted: 04/23/2012] [Indexed: 10/28/2022]
Abstract
Metal transporters are a central component in the interaction of algae with their environment. They represent the first line of defense to cellular perturbations in metal concentration, and by analyzing algal metal transporter repertoires, we gain insight into a fundamental aspect of algal biology. The ability of individual algae to thrive in environments with unique geochemistry, compared to non-algal species commonly used as reference organisms for metal homeostasis, provides an opportunity to broaden our understanding of biological metal requirements, preferences and trafficking. Chlamydomonas reinhardtii is the best developed reference organism for the study of algal biology, especially with respect to metal metabolism; however, the diversity of algal niches necessitates a comparative genomic analysis of all sequenced algal genomes. A comparison between known and putative proteins in animals, plants, fungi and algae using protein similarity networks has revealed the presence of novel metal metabolism components in Chlamydomonas including new iron and copper transporters. This analysis also supports the concept that, in terms of metal metabolism, algae from similar niches are more related to one another than to algae from the same phylogenetic clade. This article is part of a Special Issue entitled: Cell Biology of Metals.
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108
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Vogelmann K, Drechsel G, Bergler J, Subert C, Philippar K, Soll J, Engelmann JC, Engelsdorf T, Voll LM, Hoth S. Early senescence and cell death in Arabidopsis saul1 mutants involves the PAD4-dependent salicylic acid pathway. PLANT PHYSIOLOGY 2012; 159:1477-87. [PMID: 22706448 PMCID: PMC3425192 DOI: 10.1104/pp.112.196220] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 06/14/2012] [Indexed: 05/21/2023]
Abstract
Age-dependent leaf senescence and cell death in Arabidopsis (Arabidopsis thaliana) requires activation of the transcription factor ORESARA1 (ORE1) and is not initiated prior to a leaf age of 28 d. Here, we investigate the conditional execution of events that regulate early senescence and cell death in senescence-associated ubiquitin ligase1 (saul1) mutants, deficient in the PLANT U-BOX-ARMADILLO E3 ubiquitin ligase SAUL1. In saul1 mutants challenged with low light, the switch of age-dependent cell death was turned on prematurely, as indicated by the accumulation of ORE1 transcripts, induction of the senescence marker gene SENESCENCE-ASSOCIATED GENE12, and cell death. However, ORE1 accumulation by itself was not sufficient to cause saul1 phenotypes, as demonstrated by double mutant analysis. Exposure of saul1 mutants to low light for only 24 h did not result in visible symptoms of senescence; however, the senescence-promoting transcription factor genes WRKY53, WRKY6, and NAC-LIKE ACTIVATED BY AP3/PI were up-regulated, indicating that senescence in saul1 seedlings was already initiated. To resolve the time course of gene expression, microarray experiments were performed at narrow intervals. Differential expression of the genes involved in salicylic acid and defense mechanisms were the earliest events detected, suggesting a central role for salicylic acid in saul1 senescence and cell death. The salicylic acid content increased in low-light-treated saul1 mutants, and application of exogenous salicylic acid was indeed sufficient to trigger saul1 senescence in permissive light conditions. Double mutant analyses showed that PHYTOALEXIN DEFICIENT4 (PAD4) but not NONEXPRESSER OF PR GENES1 (NPR1) is essential for saul1 phenotypes. Our results indicate that saul1 senescence depends on the PAD4-dependent salicylic acid pathway but does not require NPR1 signaling.
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109
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Flores-Pérez Ú, Jarvis P. Molecular chaperone involvement in chloroplast protein import. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:332-40. [PMID: 22521451 DOI: 10.1016/j.bbamcr.2012.03.019] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 03/16/2012] [Accepted: 03/31/2012] [Indexed: 11/19/2022]
Abstract
Chloroplasts are organelles of endosymbiotic origin that perform essential functions in plants. They contain about 3000 different proteins, the vast majority of which are nucleus-encoded, synthesized in precursor form in the cytosol, and transported into the chloroplasts post-translationally. These preproteins are generally imported via envelope complexes termed TOC and TIC (Translocon at the Outer/Inner envelope membrane of Chloroplasts). They must navigate different cellular and organellar compartments (e.g., the cytosol, the outer and inner envelope membranes, the intermembrane space, and the stroma) before arriving at their final destination. It is generally considered that preproteins are imported in a largely unfolded state, and the whole process is energy-dependent. Several chaperones and cochaperones have been found to mediate different stages of chloroplast import, in similar fashion to chaperone involvement in mitochondrial import. Cytosolic factors such as Hsp90, Hsp70 and 14-3-3 may assist preproteins to reach the TOC complex at the chloroplast surface, preventing their aggregation or degradation. Chaperone involvement in the intermembrane space has also been proposed, but remains uncertain. Preprotein translocation is completed at the trans side of the inner membrane by ATP-driven motor complexes. A stromal Hsp100-type chaperone, Hsp93, cooperates with Tic110 and Tic40 in one such motor complex, while stromal Hsp70 is proposed to act in a second, parallel complex. Upon arrival in the stroma, chaperones (e.g., Hsp70, Cpn60, cpSRP43) also contribute to the folding, assembly or onward intraorganellar guidance of the proteins. In this review, we focus on chaperone involvement during preprotein translocation at the chloroplast envelope. This article is part of a Special Issue entitled: Protein Import and Quality Control in Mitochondria and Plastids.
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110
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Solti A, Kovács K, Basa B, Vértes A, Sárvári E, Fodor F. Uptake and incorporation of iron in sugar beet chloroplasts. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2012; 52:91-7. [PMID: 22305071 DOI: 10.1016/j.plaphy.2011.11.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 11/29/2011] [Indexed: 05/24/2023]
Abstract
Chloroplasts contain 80-90% of iron taken up by plant cells. Though some iron transport-related envelope proteins were identified recently, the mechanism of iron uptake into chloroplasts remained unresolved. To shed more light on the process of chloroplast iron uptake, trials were performed with isolated intact chloroplasts of sugar beet (Beta vulgaris). Iron uptake was followed by measuring the iron content of chloroplasts in the form of ferrous-bathophenantroline-disulphonate complex after solubilising the chloroplasts in reducing environment. Ferric citrate was preferred to ferrous citrate as substrate for chloroplasts. Strong dependency of ferric citrate uptake on photosynthetic electron transport activity suggests that ferric chelate reductase uses NADPH, and is localised in the inner envelope membrane. The K(m) for iron uptake from ferric-citrate pool was 14.65 ± 3.13 μM Fe((III))-citrate. The relatively fast incorporation of (57)Fe isotope into Fe-S clusters/heme, detected by Mössbauer spectroscopy, showed the efficiency of the biosynthetic machinery of these cofactors in isolated chloroplasts. The negative correlation between the chloroplast iron concentration and the rate of iron uptake refers to a strong feedback regulation of the uptake.
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Affiliation(s)
- Adám Solti
- Department of Plant Physiology and Molecular Plant Biology, Institute of Biology, Eötvös Loránd University, Pázmány P. lane 1/C, Budapest 1117, Hungary
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111
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Mehlmer N, Parvin N, Hurst CH, Knight MR, Teige M, Vothknecht UC. A toolset of aequorin expression vectors for in planta studies of subcellular calcium concentrations in Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:1751-61. [PMID: 22213817 PMCID: PMC3971373 DOI: 10.1093/jxb/err406] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Calcium has long been acknowledged as one of the most important signalling components in plants. Many abiotic and biotic stimuli are transduced into a cellular response by temporal and spatial changes in cellular calcium concentration and the calcium-sensitive protein aequorin has been exploited as a genetically encoded calcium indicator for the measurement of calcium in planta. The objective of this work was to generate a compatible set of aequorin expression plasmids for the generation of transgenic plant lines to measure changes in calcium levels in different cellular subcompartments. Aequorin was fused to different targeting peptides or organellar proteins as a means to localize it to the cytosol, the nucleus, the plasma membrane, and the mitochondria. Furthermore, constructs were designed to localize aequorin in the stroma as well as the inner and outer surface of the chloroplast envelope membranes. The modular set-up of the plasmids also allows the easy replacement of targeting sequences to include other compartments. An additional YFP-fusion was included to verify the correct subcellular localization of all constructs by laser scanning confocal microscopy. For each construct, pBin19-based binary expression vectors driven by the 35S or UBI10 promoter were made for Agrobacterium-mediated transformation. Stable Arabidopsis lines were generated and initial tests of several lines confirmed their feasibility to measure calcium signals in vivo.
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Affiliation(s)
- Norbert Mehlmer
- Department of Biology I, Botany, LMU Munich, Großhaderner Str. 2-4, D-82152 Planegg, Germany
| | - Nargis Parvin
- Department of Biology I, Botany, LMU Munich, Großhaderner Str. 2-4, D-82152 Planegg, Germany
| | - Charlotte H. Hurst
- Plant Stress Laboratory, Durham Centre for Crop Improvement Technology, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Marc R. Knight
- Plant Stress Laboratory, Durham Centre for Crop Improvement Technology, School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Markus Teige
- Department of Biochemistry, MFPL, University of Vienna, Dr. Bohr Gasse 9/5, A-1030 Vienna, Austria
| | - Ute C. Vothknecht
- Department of Biology I, Botany, LMU Munich, Großhaderner Str. 2-4, D-82152 Planegg, Germany
- Centre for Integrated Protein Science (Munich) at the Department of Biology of the LMU Munich, D-81377 Munich, Germany
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112
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Kobayashi T, Nishizawa NK. Iron uptake, translocation, and regulation in higher plants. ANNUAL REVIEW OF PLANT BIOLOGY 2012; 63:131-52. [PMID: 22404471 DOI: 10.1146/annurev-arplant-042811-105522] [Citation(s) in RCA: 644] [Impact Index Per Article: 53.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Iron is essential for the survival and proliferation of all plants. Higher plants have developed two distinct strategies to acquire iron, which is only slightly soluble, from the rhizosphere: the reduction strategy of nongraminaceous plants and the chelation strategy of graminaceous plants. Key molecular components-including transporters, enzymes, and chelators-have been clarified for both strategies, and many of these components are now thought to also function inside the plant to facilitate internal iron transport. Transporters for intracellular iron trafficking are also being clarified. A majority of genes encoding these components are transcriptionally regulated in response to iron availability. Recent research has uncovered central transcription factors, cis-acting elements, and molecular mechanisms regulating these genes. Manipulation of these molecular components has produced transgenic crops with enhanced tolerance to iron deficiency or with increased iron content in the edible parts.
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Affiliation(s)
- Takanori Kobayashi
- Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Nonoichi, Ishikawa, Japan.
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113
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Biochemical and Functional Responses of Arabidopsis thaliana Exposed to Cadmium, Copper and Zinc. THE PLANT FAMILY BRASSICACEAE 2012. [DOI: 10.1007/978-94-007-3913-0_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/06/2022]
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114
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Lamberti G, Drurey C, Soll J, Schwenkert S. The phosphorylation state of chloroplast transit peptides regulates preprotein import. PLANT SIGNALING & BEHAVIOR 2011; 6:1918-20. [PMID: 22105029 PMCID: PMC3337178 DOI: 10.4161/psb.6.12.18127] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Import of nuclear encoded proteins into chloroplast is an essential and well-regulated mechanism. The cytosolic kinases STY8, STY17 and STY46 have been shown to phosphorylate chloroplast preprotein transit peptides advantaging the binding of a 14-3-3 dimer. Analyses of sty8 sty17 sty46 mutant plants revealed a role for the kinases in chloroplast differentiation, possibly due to lack of transit peptide phosphorylation. Moreover we could show that not only phosphorylation but also transit peptide dephosphorylation appears to be required for the fine regulation of the back-transport of nuclear encoded proteins to the chloroplast.
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Affiliation(s)
- Giorgia Lamberti
- Department of Biology I, Botany; Ludwig-Maximilians-Universität München; Planegg-Martinsried, Germany
- Munich Center for Integrated Protein Science (CiPSM); Ludwig-Maximilians-Universität München; Munich, Germany
| | - Claire Drurey
- Department of Biology I, Botany; Ludwig-Maximilians-Universität München; Planegg-Martinsried, Germany
| | - Jürgen Soll
- Department of Biology I, Botany; Ludwig-Maximilians-Universität München; Planegg-Martinsried, Germany
- Munich Center for Integrated Protein Science (CiPSM); Ludwig-Maximilians-Universität München; Munich, Germany
| | - Serena Schwenkert
- Department of Biology I, Botany; Ludwig-Maximilians-Universität München; Planegg-Martinsried, Germany
- Munich Center for Integrated Protein Science (CiPSM); Ludwig-Maximilians-Universität München; Munich, Germany
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115
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Ramirez L, Simontacchi M, Murgia I, Zabaleta E, Lamattina L. Nitric oxide, nitrosyl iron complexes, ferritin and frataxin: a well equipped team to preserve plant iron homeostasis. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2011; 181:582-92. [PMID: 21893255 DOI: 10.1016/j.plantsci.2011.04.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 04/12/2011] [Accepted: 04/13/2011] [Indexed: 05/08/2023]
Abstract
Iron is a key element in plant nutrition. Iron deficiency as well as iron overload results in serious metabolic disorders that affect photosynthesis, respiration and general plant fitness with direct consequences on crop production. More than 25% of the cultivable land possesses low iron availability due to high pH (calcareous soils). Plant biologists are challenged by this concern and aimed to find new avenues to ameliorate plant responses and keep iron homeostasis under control even at wide range of iron availability in various soils. For this purpose, detailed knowledge of iron uptake, transport, storage and interactions with cellular compounds will help to construct a more complete picture of its role as essential nutrient. In this review, we summarize and describe the recent findings involving four central players involved in keeping cellular iron homeostasis in plants: nitric oxide, ferritin, frataxin and nitrosyl iron complexes. We attempt to highlight the interactions among these actors in different scenarios occurring under iron deficiency or iron overload, and discuss their counteracting and/or coordinating actions leading to the control of iron homeostasis.
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Affiliation(s)
- Leonor Ramirez
- Instituto de Investigaciones Biológicas, Universidad Nacional de Mar del Plata-CONICET, CC 1245 Mar del Plata, Argentina
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116
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Kovács-Bogdán E, Benz JP, Soll J, Bölter B. Tic20 forms a channel independent of Tic110 in chloroplasts. BMC PLANT BIOLOGY 2011; 11:133. [PMID: 21961525 PMCID: PMC3203047 DOI: 10.1186/1471-2229-11-133] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Accepted: 09/30/2011] [Indexed: 05/20/2023]
Abstract
BACKGROUND The Tic complex (Translocon at the inner envelope membrane of chloroplasts) mediates the translocation of nuclear encoded chloroplast proteins across the inner envelope membrane. Tic110 forms one prominent protein translocation channel. Additionally, Tic20, another subunit of the complex, was proposed to form a protein import channel - either together with or independent of Tic110. However, no experimental evidence for Tic20 channel activity has been provided so far. RESULTS We performed a comprehensive biochemical and electrophysiological study to characterize Tic20 in more detail and to gain a deeper insight into its potential role in protein import into chloroplasts. Firstly, we compared transcript and protein levels of Tic20 and Tic110 in both Pisum sativum and Arabidopsis thaliana. We found the Tic20 protein to be generally less abundant, which was particularly pronounced in Arabidopsis. Secondly, we demonstrated that Tic20 forms a complex larger than 700 kilodalton in the inner envelope membrane, which is clearly separate from Tic110, migrating as a dimer at about 250 kilodalton. Thirdly, we defined the topology of Tic20 in the inner envelope, and found its N- and C-termini to be oriented towards the stromal side. Finally, we successfully reconstituted overexpressed and purified full-length Tic20 into liposomes. Using these Tic20-proteoliposomes, we could demonstrate for the first time that Tic20 can independently form a cation selective channel in vitro. CONCLUSIONS The presented data provide first biochemical evidence to the notion that Tic20 can act as a channel protein within the chloroplast import translocon complex. However, the very low abundance of Tic20 in the inner envelope membranes indicates that it cannot form a major protein translocation channel. Furthermore, the independent complex formation of Tic20 and Tic110 argues against a joint channel formation. Thus, based on the observed channel activity of Tic20 in proteoliposomes, we speculate that the chloroplast inner envelope contains multiple (at least two) translocation channels: Tic110 as the general translocation pore, whereas Tic20 could be responsible for translocation of a special subset of proteins.
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Affiliation(s)
- Erika Kovács-Bogdán
- Ludwig-Maximilians-Universität München, Department Biologie I, Plant Biochemistry, Grosshaderner Str. 2-4, D-82152 Planegg-Martinsried, Germany
- Munich Center for Integrated Protein Science CiPS, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany
| | - J Philipp Benz
- Ludwig-Maximilians-Universität München, Department Biologie I, Plant Biochemistry, Grosshaderner Str. 2-4, D-82152 Planegg-Martinsried, Germany
- Munich Center for Integrated Protein Science CiPS, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany
- Energy Biosciences Institute, University of California Berkeley, Berkeley, CA 94720, USA
| | - Jürgen Soll
- Ludwig-Maximilians-Universität München, Department Biologie I, Plant Biochemistry, Grosshaderner Str. 2-4, D-82152 Planegg-Martinsried, Germany
- Munich Center for Integrated Protein Science CiPS, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany
| | - Bettina Bölter
- Ludwig-Maximilians-Universität München, Department Biologie I, Plant Biochemistry, Grosshaderner Str. 2-4, D-82152 Planegg-Martinsried, Germany
- Munich Center for Integrated Protein Science CiPS, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany
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Lamberti G, Gügel IL, Meurer J, Soll J, Schwenkert S. The cytosolic kinases STY8, STY17, and STY46 are involved in chloroplast differentiation in Arabidopsis. PLANT PHYSIOLOGY 2011; 157:70-85. [PMID: 21799034 PMCID: PMC3165899 DOI: 10.1104/pp.111.182774] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
In Arabidopsis (Arabidopsis thaliana), transit peptides for chloroplast-destined preproteins can be phosphorylated by the protein kinases STY8, STY17, and STY46. In this study, we have investigated the in vitro properties of these plant-specific kinases. Characterization of the mechanistic functioning of STY8 led to the identification of an essential threonine in the activation segment, which is phosphorylated by an intramolecular mechanism. STY8 is inhibited by specific tyrosine kinase inhibitors, although it lacked the ability to phosphorylate tyrosine residues in vitro. In vivo analysis of sty8, sty17, and sty46 Arabidopsis knockout/knockdown mutants revealed a distinct function of the three kinases in the greening process and in the efficient differentiation of chloroplasts. Mutant plants displayed not only a delayed accumulation of chlorophyll but also a reduction of nucleus-encoded chloroplast proteins and a retarded establishment of photosynthetic capacity during the first 6 h of deetiolation, supporting a role of cytosolic STY kinases in chloroplast differentiation.
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118
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The rice mitochondrial iron transporter is essential for plant growth. Nat Commun 2011; 2:322. [PMID: 21610725 PMCID: PMC3113228 DOI: 10.1038/ncomms1326] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 04/26/2011] [Indexed: 11/18/2022] Open
Abstract
In plants, iron (Fe) is essential for mitochondrial electron transport, heme, and Fe-Sulphur (Fe-S) cluster synthesis; however, plant mitochondrial Fe transporters have not been identified. Here we show, identify and characterize the rice mitochondrial Fe transporter (MIT). Based on a transfer DNA library screen, we identified a rice line showing symptoms of Fe deficiency while accumulating high shoot levels of Fe. Homozygous knockout of MIT in this line resulted in a lethal phenotype. MIT localized to the mitochondria and complemented the growth of Δmrs3Δmrs4 yeast defective in mitochondrial Fe transport. The growth of MIT-knockdown (mit-2) plants was also significantly impaired despite abundant Fe accumulation. Further, the decrease in the activity of the mitochondrial and cytosolic Fe-S enzyme, aconitase, indicated that Fe-S cluster synthesis is affected in mit-2 plants. These results indicate that MIT is a mitochondrial Fe transporter essential for rice growth and development. Increasing the nutritional content of plant crops and the identification of iron transporters in rice would facilitate the improvement of rice varieties. In this study, the authors identify a mitochondrial iron transporter in rice — MIT — and suggest that this gene is important for rice growth and development.
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119
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Kurdrid P, Senachak J, Sirijuntarut M, Yutthanasirikul R, Phuengcharoen P, Jeamton W, Roytrakul S, Cheevadhanarak S, Hongsthong A. Comparative analysis of the Spirulina platensis subcellular proteome in response to low- and high-temperature stresses: uncovering cross-talk of signaling components. Proteome Sci 2011; 9:39. [PMID: 21756373 PMCID: PMC3162491 DOI: 10.1186/1477-5956-9-39] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Accepted: 07/15/2011] [Indexed: 11/23/2022] Open
Abstract
The present study focused on comparative proteome analyses of low- and high-temperature stresses and potential protein-protein interaction networks, constructed by using a bioinformatics approach, in response to both stress conditions. The data revealed two important points: first, the results indicate that low-temperature stress is tightly linked with oxidative stress as well as photosynthesis; however, no specific mechanism is revealed in the case of the high-temperature stress response. Second, temperature stress was revealed to be linked with nitrogen and ammonia assimilation. Moreover, the data also highlighted the cross-talk of signaling pathways. Some of the detected signaling proteins, e.g., Hik14, Hik26 and Hik28, have potential interactions with differentially expressed proteins identified in both temperature stress conditions. Some differentially expressed proteins found in the Spirulina protein-protein interaction network were also examined for their physical interactions by a yeast two hybrid system (Y2H). The Y2H results obtained in this study suggests that the potential PPI network gives quite reliable potential interactions for Spirulina. Therefore, the bioinformatics approach employed in this study helps in the analysis of phenomena where proteome analyses of knockout mutants have not been carried out to directly examine for specificity or cross-talk of signaling components.
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Affiliation(s)
- Pavinee Kurdrid
- BEC Unit, National Center for Genetic Engineering and Biotechnology, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
| | - Jittisak Senachak
- BEC Unit, National Center for Genetic Engineering and Biotechnology, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
| | - Matura Sirijuntarut
- Pilot Plant Development and Training Institute, King Mongkut's University of Technology Thonburi, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
| | - Rayakorn Yutthanasirikul
- Pilot Plant Development and Training Institute, King Mongkut's University of Technology Thonburi, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
| | - Phuttawadee Phuengcharoen
- Pilot Plant Development and Training Institute, King Mongkut's University of Technology Thonburi, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
| | - Wattana Jeamton
- Pilot Plant Development and Training Institute, King Mongkut's University of Technology Thonburi, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
| | - Sittiruk Roytrakul
- BEC Unit, National Center for Genetic Engineering and Biotechnology, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
| | - Supapon Cheevadhanarak
- School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
| | - Apiradee Hongsthong
- BEC Unit, National Center for Genetic Engineering and Biotechnology, 49 Soi Theintalay 25, Thakham, Bangkhuntien, Bangkok, 10150, Thailand
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Csog Á, Mihucz VG, Tatár E, Fodor F, Virág I, Majdik C, Záray G. Accumulation and distribution of iron, cadmium, lead and nickel in cucumber plants grown in hydroponics containing two different chelated iron supplies. JOURNAL OF PLANT PHYSIOLOGY 2011; 168:1038-1044. [PMID: 21342715 DOI: 10.1016/j.jplph.2010.12.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 12/13/2010] [Accepted: 12/14/2010] [Indexed: 05/30/2023]
Abstract
Cucumber plants grown in hydroponics containing 10 μM Cd(II), Ni(II) and Pb(II), and iron supplied as Fe(III) EDTA or Fe(III) citrate in identical concentrations, were investigated by total-reflection X-ray fluorescence spectrometry with special emphasis on the determination of iron accumulation and distribution within the different plant compartments (root, stem, cotyledon and leaves). The extent of Cd, Ni and Pb accumulation and distribution were also determined. Generally, iron and heavy-metal contaminant accumulation was higher when Fe(III) citrate was used. The accumulation of nickel and lead was higher by about 20% and 100%, respectively, if the iron supply was Fe(III) citrate. The accumulation of Cd was similar. In the case of Fe(III) citrate, the total amounts of Fe taken up were similar in the control and heavy-metal-treated plants (27-31 μmol/plant). Further, the amounts of iron transported from the root towards the shoot of the control, lead- and nickel-contaminated plants were independent of the iron(III) form. Although Fe mobility could be characterized as being low, its distribution within the shoot was not significantly affected by the heavy metals investigated.
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Affiliation(s)
- Árpád Csog
- Department of Chemical Technology, Faculty of Chemistry and Chemical Engineering, Babeş-Bolyai University, Arany János 11, Cluj-Napoca RO-3400, Romania
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Nouet C, Motte P, Hanikenne M. Chloroplastic and mitochondrial metal homeostasis. TRENDS IN PLANT SCIENCE 2011; 16:395-404. [PMID: 21489854 DOI: 10.1016/j.tplants.2011.03.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Revised: 02/25/2011] [Accepted: 03/07/2011] [Indexed: 05/03/2023]
Abstract
Transition metal deficiency has a strong impact on the growth and survival of an organism. Indeed, transition metals, such as iron, copper, manganese and zinc, constitute essential cofactors for many key cellular functions. Both photosynthesis and respiration rely on metal cofactor-mediated electron transport chains. Chloroplasts and mitochondria are, therefore, organelles with high metal ion demand and represent essential components of the metal homeostasis network in photosynthetic cells. In this review, we describe the metal requirements of chloroplasts and mitochondria, the acclimation of their functions to metal deficiency and recent advances in our understanding of their contributions to cellular metal homeostasis, the control of the cellular redox status and the synthesis of metal cofactors.
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Affiliation(s)
- Cécile Nouet
- Functional Genomics and Plant Molecular Imaging, Center for Protein Engineering, Department of Life Sciences (B22), University of Liège, Belgium
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122
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Bölter B, Soll J. Protein Import into Chloroplasts: Dealing with the (Membrane) Integration Problem. Chembiochem 2011; 12:1655-61. [DOI: 10.1002/cbic.201100118] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Indexed: 11/10/2022]
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Schuler M, Keller A, Backes C, Philippar K, Lenhof HP, Bauer P. Transcriptome analysis by GeneTrail revealed regulation of functional categories in response to alterations of iron homeostasis in Arabidopsis thaliana. BMC PLANT BIOLOGY 2011; 11:87. [PMID: 21592396 PMCID: PMC3114716 DOI: 10.1186/1471-2229-11-87] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2010] [Accepted: 05/18/2011] [Indexed: 05/04/2023]
Abstract
BACKGROUND High-throughput technologies have opened new avenues to study biological processes and pathways. The interpretation of the immense amount of data sets generated nowadays needs to be facilitated in order to enable biologists to identify complex gene networks and functional pathways. To cope with this task multiple computer-based programs have been developed. GeneTrail is a freely available online tool that screens comparative transcriptomic data for differentially regulated functional categories and biological pathways extracted from common data bases like KEGG, Gene Ontology (GO), TRANSPATH and TRANSFAC. Additionally, GeneTrail offers a feature that allows screening of individually defined biological categories that are relevant for the respective research topic. RESULTS We have set up GeneTrail for the use of Arabidopsis thaliana. To test the functionality of this tool for plant analysis, we generated transcriptome data of root and leaf responses to Fe deficiency and the Arabidopsis metal homeostasis mutant nas4x-1. We performed Gene Set Enrichment Analysis (GSEA) with eight meaningful pairwise comparisons of transcriptome data sets. We were able to uncover several functional pathways including metal homeostasis that were affected in our experimental situations. Representation of the differentially regulated functional categories in Venn diagrams uncovered regulatory networks at the level of whole functional pathways. Over-Representation Analysis (ORA) of differentially regulated genes identified in pairwise comparisons revealed specific functional plant physiological categories as major targets upon Fe deficiency and in nas4x-1. CONCLUSION Here, we obtained supporting evidence, that the nas4x-1 mutant was defective in metal homeostasis. It was confirmed that nas4x-1 showed Fe deficiency in roots and signs of Fe deficiency and Fe sufficiency in leaves. Besides metal homeostasis, biotic stress, root carbohydrate, leaf photosystem and specific cell biological categories were discovered as main targets for regulated changes in response to--Fe and nas4x-1. Among 258 differentially expressed genes in response to--Fe and nas4x-1 five functional categories were enriched covering metal homeostasis, redox regulation, cell division and histone acetylation. We proved that GeneTrail offers a flexible and user-adapted way to identify functional categories in large-scale plant transcriptome data sets. The distinguished feature that allowed analysis of individually assembled functional categories facilitated the study of the Arabidopsis thaliana transcriptome.
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Affiliation(s)
- Mara Schuler
- Dept. of Biosciences - Botany, Campus A2.4, Saarland University, D-66123 Saarbrücken, Germany
| | - Andreas Keller
- Dept. of Informatics - Center for Bioinformatics, Campus E1.1, Saarland University, D-66123 Saarbrücken, Germanys
| | - Christina Backes
- Dept. of Informatics - Center for Bioinformatics, Campus E1.1, Saarland University, D-66123 Saarbrücken, Germanys
| | - Katrin Philippar
- Dept. Biology I - Plant Biochemistry and Physiology, Biocenter of the Ludwig-Maximilians-University München, Großhadernerstr. 2-4, D-82152 Planegg-Martinsried, Germany
| | - Hans-Peter Lenhof
- Dept. of Informatics - Center for Bioinformatics, Campus E1.1, Saarland University, D-66123 Saarbrücken, Germanys
| | - Petra Bauer
- Dept. of Biosciences - Botany, Campus A2.4, Saarland University, D-66123 Saarbrücken, Germany
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Abadía J, Vázquez S, Rellán-Álvarez R, El-Jendoubi H, Abadía A, Alvarez-Fernández A, López-Millán AF. Towards a knowledge-based correction of iron chlorosis. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2011; 49:471-82. [PMID: 21349731 DOI: 10.1016/j.plaphy.2011.01.026] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 01/25/2011] [Accepted: 01/26/2011] [Indexed: 05/20/2023]
Abstract
Iron (Fe) deficiency-induced chlorosis is a major nutritional disorder in crops growing in calcareous soils. Iron deficiency in fruit tree crops causes chlorosis, decreases in vegetative growth and marked fruit yield and quality losses. Therefore, Fe fertilizers, either applied to the soil or delivered to the foliage, are used every year to control Fe deficiency in these crops. On the other hand, a substantial body of knowledge is available on the fundamentals of Fe uptake, long and short distance Fe transport and subcellular Fe allocation in plants. Most of this basic knowledge, however, applies only to Fe deficiency, with studies involving Fe fertilization (i.e., with Fe-deficient plants resupplied with Fe) being still scarce. This paper reviews recent developments in Fe-fertilizer research and the state-of-the-art of the knowledge on Fe acquisition, transport and utilization in plants. Also, the effects of Fe-fertilization on the plant responses to Fe deficiency are reviewed. Agronomical Fe-fertilization practices should benefit from the basic knowledge on plant Fe homeostasis already available; this should be considered as a long-term goal that can optimize fertilizer inputs, reduce grower's costs and minimize the environmental impact of fertilization.
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Affiliation(s)
- Javier Abadía
- Department of Plant Nutrition, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), P.O. BOX 13034, E-50080 Zaragoza, Spain.
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125
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Gollhofer J, Schläwicke C, Jungnick N, Schmidt W, Buckhout TJ. Members of a small family of nodulin-like genes are regulated under iron deficiency in roots of Arabidopsis thaliana. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2011; 49:557-64. [PMID: 21411332 DOI: 10.1016/j.plaphy.2011.02.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2010] [Accepted: 02/12/2011] [Indexed: 05/06/2023]
Abstract
The analysis of rapid responses in the transcriptome of Arabidopsis roots to a decreased iron (Fe) supply was studied using DNA microarrays and revealed candidate genes with putative roles in Fe homeostasis. In addition to the frequently reported induction of gene activity in response to Fe deficiency, the expression of a number of putative cationic metal transporters was found to rapidly decrease in response to Fe deficiency. In this report we have investigated a small family of five nodulin-like genes that show protein sequence similarity to AtVIT1 and likely have a function in regulation of Fe homeostasis. DNA microarray analysis showed a rapid decrease in transcript abundance for nodulin-like1 (At1g21140), nodulin-like2 (At1g76800), and nodulin-like21 (At3g25190). This decrease was significant after 6 h of Fe deficiency and persisted at least to 72 h. Nodulin-like3 (At3g43630) and Nodulin-like4 (At3g43660) did not respond to the Fe concentration in the microarray analysis. The nodulin-like family encoded presumptive membrane proteins with five calculated transmembrane domains, and all members had significant protein sequence homology to the vacuolar Fe transporters AtVIT1 and ScCCC1p. Homologs of all five nodulin-like genes were found in both di- and monocotyledon plants, as well as in Physcomitrella and Chlamydomonas. Promoter-β-glucuronidase (GUS) assays showed expression of the nodulin-like1 gene in roots, hypocotyls, and expanded cotyledons of two-week-old Arabidopsis seedlings with the greatest activity associated with the vascular bundle and the root stele. In the absence of Fe, GUS activity was greatly reduced and was only weakly visible in the stele and vascular bundle. In an attempt to identify the function of these nodulin-like proteins, we isolated knockout mutants for nodulin-like3 and nodulin-like21 from available T-DNA insertion lines. Although these mutants did not show dramatic changes in growth or in their ability to grow on Fe-deficient media or media containing from 5 to 120 μM Fe, the nodulin-like3 mutant had a significantly higher Fe concentration in the shoots and both nodulin-like3 and nodulin-like21 mutants had significantly decreased Fe in the roots. These results were taken as an indication, that some members of this nodulin-like family were directly involved in Fe homeostasis in plants.
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Affiliation(s)
- Julia Gollhofer
- Applied Botany, Humboldt University Berlin, Invalidenstraße 42, 10115 Berlin, Germany
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126
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Tarantino D, Morandini P, Ramirez L, Soave C, Murgia I. Identification of an Arabidopsis mitoferrinlike carrier protein involved in Fe metabolism. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2011; 49:520-9. [PMID: 21371898 DOI: 10.1016/j.plaphy.2011.02.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Accepted: 02/03/2011] [Indexed: 05/22/2023]
Abstract
Iron has a major role in mitochondrial as well as in chloroplast metabolism, however the processes involved in organelle iron transport in plants are only partially understood. To identify mitochondrial iron transporters in Arabidopsis, we searched for proteins homologous to the Danio rerio (zebrafish) Mitoferrin2 MFRN2, a mitochondrial iron importer in non-erythroid cells. Among the identified putative Arabidopsis mitoferrinlike proteins, we focused on that one encoded by At5g42130, which we named AtMfl1 (MitoFerrinLike1). AtMfl1 expression strongly correlates with genes coding for proteins involved in chloroplast metabolism. Such an unexpected result is supported by the identification by different research groups, of the protein encoded by At5g42130 and of its homologs from various plant species in the inner chloroplastic envelope membrane proteome. Notably, neither the protein encoded by At5g42130 nor its homologs from other plant species have been identified in the mitochondrial proteome. AtMfl1 gene expression is dependent on Fe supply: AtMfl1 transcript strongly accumulates under Fe excess, moderately under Fe sufficiency and weakly under Fe deficiency. In order to understand the physiological role of AtMfl1, we isolated and characterized two independent AtMfl1 KO mutants, atmfl1-1 and atmfl1-2: both show reduced vegetative growth. When grown under conditions of Fe excess, atmfl1-1 and atmfl1-2 mutants (seedlings, rosette leaves) contain less total Fe than wt and also reduced expression of the iron storage ferritin AtFer1. Taken together, these results suggest that Arabidopsis mitoferrinlike gene AtMfl1 is involved in Fe transport into chloroplasts, under different conditions of Fe supply and that suppression of its expression alters plant Fe accumulation in various developmental stages.
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Affiliation(s)
- Delia Tarantino
- Sezione di Fisiologia e Biochimica delle Piante, Dipartimento di Biologia, Università degli Studi di Milano, via Celoria 26, 20133 Italy
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Conte SS, Walker EL. Transporters contributing to iron trafficking in plants. MOLECULAR PLANT 2011; 4:464-76. [PMID: 21447758 DOI: 10.1093/mp/ssr015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
This review will discuss recent progress in understanding the many roles of transporters in the whole-plant physiological processes that maintain iron (Fe) homeostasis. These processes include uptake from the soil via roots, control of transport from roots to above-ground parts of the plant, unloading of Fe from the xylem in above-ground parts, loading of Fe into mitochondria and plastids, transport of Fe to reproductive parts of the plant, and Fe mobilization during seed germination. In addition, we will discuss the mechanisms that plants use to cope with an apparently unintended consequence of Fe acquisition: the uptake of toxic heavy metals via Fe transporters. Rapid progress has been made in understanding the transport processes involved in each of these areas in the last 5 years and this review will focus on this recent progress. We will also highlight the key questions regarding transport steps that remain to be elucidated.
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Affiliation(s)
- Sarah S Conte
- University of Massachusetts Amherst, Biology Department, 611 No. Pleasant St, Amherst, MA 01002, USA
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128
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Mikami Y, Saito A, Miwa E, Higuchi K. Allocation of Fe and ferric chelate reductase activities in mesophyll cells of barley and sorghum under Fe-deficient conditions. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2011; 49:513-9. [PMID: 21288731 DOI: 10.1016/j.plaphy.2011.01.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Accepted: 01/06/2011] [Indexed: 05/09/2023]
Abstract
Although the photosynthetic apparatus requires large amounts of Fe, the adaptive mechanisms of mesophyll cells for Fe acquisition under Fe-deficient conditions are unknown. Barley and sorghum, which are tolerant and susceptible to Fe deficiency, respectively, have similar Fe and chlorophyll contents in their leaves. However, the Fe-deficient barley photosynthetic apparatus was functional while that of sorghum was not. We show that barley preferentially allocates Fe to thylakoid membranes under Fe-deficient conditions. On the other hand, in sorghum, the proportion of leaf Fe allocated to thylakoids was not altered by Fe deficiency. The relationship between the maintenance of photosynthesis and light-dependent ferric chelate reductase activity on plasma membranes and chloroplast envelopes is also discussed.
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Affiliation(s)
- Yuichiro Mikami
- Laboratory of Plant Production Chemistry, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan
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Duy D, Stübe R, Wanner G, Philippar K. The chloroplast permease PIC1 regulates plant growth and development by directing homeostasis and transport of iron. PLANT PHYSIOLOGY 2011; 155:1709-22. [PMID: 21343424 PMCID: PMC3091129 DOI: 10.1104/pp.110.170233] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The membrane-spanning protein PIC1 (for permease in chloroplasts 1) in Arabidopsis (Arabidopsis thaliana) was previously described to mediate iron transport across the inner envelope membrane of chloroplasts. The albino phenotype of pic1 knockout mutants was reminiscent of iron-deficiency symptoms and characterized by severely impaired plastid development and plant growth. In addition, plants lacking PIC1 showed a striking increase in chloroplast ferritin clusters, which function in protection from oxidative stress by sequestering highly reactive free iron in their spherical protein shell. In contrast, PIC1-overexpressing lines (PIC1ox) in this study rather resembled ferritin loss-of-function plants. PIC1ox plants suffered from oxidative stress and leaf chlorosis, most likely originating from iron overload in chloroplasts. Later during growth, plants were characterized by reduced biomass as well as severely defective flower and seed development. As a result of PIC1 protein increase in the inner envelope membrane of plastids, flower tissue showed elevated levels of iron, while the content of other transition metals (copper, zinc, manganese) remained unchanged. Seeds, however, specifically revealed iron deficiency, suggesting that PIC1 overexpression sequestered iron in flower plastids, thereby becoming unavailable for seed iron loading. In addition, expression of genes associated with metal transport and homeostasis as well as photosynthesis was deregulated in PIC1ox plants. Thus, PIC1 function in plastid iron transport is closely linked to ferritin and plastid iron homeostasis. In consequence, PIC1 is crucial for balancing plant iron metabolism in general, thereby regulating plant growth and in particular fruit development.
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Fischer K. The import and export business in plastids: transport processes across the inner envelope membrane. PLANT PHYSIOLOGY 2011; 155:1511-9. [PMID: 21263040 PMCID: PMC3091126 DOI: 10.1104/pp.110.170241] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2010] [Accepted: 01/20/2011] [Indexed: 05/17/2023]
Affiliation(s)
- Karsten Fischer
- Institute for Arctic and Marine Biology, University of Tromsø, 9037 Tromsø, Norway.
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131
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Duy D, Stübe R, Wanner G, Philippar K. The chloroplast permease PIC1 regulates plant growth and development by directing homeostasis and transport of iron. PLANT PHYSIOLOGY 2011; 155:1709-1722. [PMID: 21343424 DOI: 10.1104/pp110170233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The membrane-spanning protein PIC1 (for permease in chloroplasts 1) in Arabidopsis (Arabidopsis thaliana) was previously described to mediate iron transport across the inner envelope membrane of chloroplasts. The albino phenotype of pic1 knockout mutants was reminiscent of iron-deficiency symptoms and characterized by severely impaired plastid development and plant growth. In addition, plants lacking PIC1 showed a striking increase in chloroplast ferritin clusters, which function in protection from oxidative stress by sequestering highly reactive free iron in their spherical protein shell. In contrast, PIC1-overexpressing lines (PIC1ox) in this study rather resembled ferritin loss-of-function plants. PIC1ox plants suffered from oxidative stress and leaf chlorosis, most likely originating from iron overload in chloroplasts. Later during growth, plants were characterized by reduced biomass as well as severely defective flower and seed development. As a result of PIC1 protein increase in the inner envelope membrane of plastids, flower tissue showed elevated levels of iron, while the content of other transition metals (copper, zinc, manganese) remained unchanged. Seeds, however, specifically revealed iron deficiency, suggesting that PIC1 overexpression sequestered iron in flower plastids, thereby becoming unavailable for seed iron loading. In addition, expression of genes associated with metal transport and homeostasis as well as photosynthesis was deregulated in PIC1ox plants. Thus, PIC1 function in plastid iron transport is closely linked to ferritin and plastid iron homeostasis. In consequence, PIC1 is crucial for balancing plant iron metabolism in general, thereby regulating plant growth and in particular fruit development.
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Affiliation(s)
- Daniela Duy
- Biochemie und Physiologie der Pflanzen, Department Biologie I-Botanik, Ludwig-Maximilians-Universität München, D-82152 Planegg-Martinsried, Germany
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132
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Chan CX, Gross J, Yoon HS, Bhattacharya D. Plastid origin and evolution: new models provide insights into old problems. PLANT PHYSIOLOGY 2011; 155:1552-60. [PMID: 21343425 PMCID: PMC3091110 DOI: 10.1104/pp.111.173500] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 02/19/2011] [Indexed: 05/18/2023]
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133
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Jia L, Wu Z, Hao X, Carrie C, Zheng L, Whelan J, Wu Y, Wang S, Wu P, Mao C. Identification of a novel mitochondrial protein, short postembryonic roots 1 (SPR1), involved in root development and iron homeostasis in Oryza sativa. THE NEW PHYTOLOGIST 2011; 189:843-855. [PMID: 21039568 DOI: 10.1111/j.1469-8137.2010.03513.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
• A rice mutant, Oryza sativa short postembryonic roots 1 (Osspr1), has been characterized. It has short postembryonic roots, including adventitious and lateral roots, and a lower iron content in its leaves. • OsSPR1 was identified by map-based cloning. It encodes a novel mitochondrial protein with the Armadillo-like repeat domain. • Osspr1 mutants exhibited decreased root cell elongation. The iron content of the mutant shoots was significantly altered compared with that of wild-type shoots. A similar pattern of alteration of manganese and zinc concentrations in shoots was also observed. Complementation of the mutant confirmed that OsSPR1 is involved in post-embryonic root elongation and iron homeostasis in rice. OsSPR1 was found to be ubiquitously expressed in various tissues throughout the plant. The transcript abundance of various genes involved in iron uptake and signaling via both strategies I and II was similar in roots of wild-type and mutant plants, but was higher in the leaves of mutant plants. • Thus, a novel mitochondrial protein that is involved in root elongation and plays a role in metal ion homeostasis has been identified.
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Affiliation(s)
- Liqiang Jia
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Zhongchang Wu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Xi Hao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Chris Carrie
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, 6009 WA, Australia
- Joint Laboratory in Genomics and Nutriomics, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Libin Zheng
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - James Whelan
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, 6009 WA, Australia
- Joint Laboratory in Genomics and Nutriomics, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Yunrong Wu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Shoufeng Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Ping Wu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China
| | - Chuanzao Mao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou 310058, China
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135
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Zhang Y, Shi R, Rezaul KM, Zhang F, Zou C. Iron and zinc concentrations in grain and flour of winter wheat as affected by foliar application. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2010; 58:12268-74. [PMID: 21073194 DOI: 10.1021/jf103039k] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Human deficiencies of iron (Fe) and zinc (Zn) are worldwide problems. Biofortification of wheat could reduce Fe and Zn deficiencies in societies that depend on wheat consumption. This study investigated the effects of foliar application of Fe with or without Zn on the concentrations of Fe and Zn in grain and especially in flour of three wheat cultivars. On average, grain Fe concentration was increased significantly from 29.5 mg kg(-1) in the control to 37.8, 35.9, or 34.9 mg kg(-1) by application of FeSO4, ferric citrate plus ZnSO4, or ferric citrate, respectively. As expected, grain Zn concentration was increased from 29.0 mg kg(-1) in the control to 45.7 or 39.6 mg kg(-1) by application of ferric citrate plus ZnSO4 or a complex of micronutrients. Although the Fe and Zn concentrations in flour were inherently lower than in bran and shorts made by experimental mill, the concentrations in flour were simultaneously increased from 10.4 to 12.4 mg kg(-1) for Fe and from 11.8 to 17.4 mg kg(-1) for Zn by application of ferric citrate plus ZnSO4. Importantly, Fe was peripherally localized within grain fractions and strictly limited to transport to endosperm, making it more difficult to increase the quantity of Fe in flour products by foliar Fe application, but the situation with Zn is promising because Zn is more readily transported to the endosperm than Fe. The current study increases the understanding of agronomic biofortification.
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Affiliation(s)
- Yueqiang Zhang
- Key Laboratory of Plant-Soil Interaction, MOE, and Key Laboratory of Plant Nutrition, MOA, Department of Plant Nutrition, China Agricultural University, Beijing 100193, People's Republic of China
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136
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Vesicle-related OsSEC27P enhances H+ secretion in the iron deficient transgenic tobacco root. ACTA ACUST UNITED AC 2010. [DOI: 10.1007/s11434-010-4012-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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137
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Schwenkert S, Soll J, Bölter B. Protein import into chloroplasts--how chaperones feature into the game. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:901-11. [PMID: 20682282 DOI: 10.1016/j.bbamem.2010.07.021] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 07/20/2010] [Accepted: 07/21/2010] [Indexed: 11/15/2022]
Abstract
Chloroplasts originated from an endosymbiotic event, in which an ancestral photosynthetic cyanobacterium was engulfed by a mitochondriate eukaryotic host cell. During evolution, the endosymbiont lost its autonomy by means of a massive transfer of genetic information from the prokaryotic genome to the host nucleus. Consequently, the development of protein import machineries became necessary for the relocation of proteins that are now nuclear-encoded and synthesized in the cytosol but destined for the chloroplast. Organelle biogenesis and maintenance requires a tight coordination of transcription, translation and protein import between the host cell and the organelle. This review focuses on the translocation complexes in the outer and inner envelope membrane with a special emphasis on the role of molecular chaperones. This article is part of a Special Issue entitled Protein translocation across or insertion into membranes.
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Affiliation(s)
- Serena Schwenkert
- Department Biologie I-Botanik, Ludwig-Maximilians-Universität, Großhadernerstr 2-4, D-82152 Planegg-Martinsried, Germany
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138
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Bodył A, Mackiewicz P, Stiller JW. Comparative genomic studies suggest that the cyanobacterial endosymbionts of the amoeba Paulinella chromatophora possess an import apparatus for nuclear-encoded proteins. PLANT BIOLOGY (STUTTGART, GERMANY) 2010; 12:639-649. [PMID: 20636907 DOI: 10.1111/j.1438-8677.2009.00264.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Plastids evolved from free-living cyanobacteria through a process of primary endosymbiosis. The most widely accepted hypothesis derives three ancient lineages of primary plastids, i.e. those of glaucophytes, red algae and green plants, from a single cyanobacterial endosymbiosis. This hypothesis was originally predicated on the assumption that transformations of endosymbionts into organelles must be exceptionally rare because of the difficulty in establishing efficient protein trafficking between a host cell and incipient organelle. It turns out, however, that highly integrated endosymbiotic associations are more common than once thought. Among them is the amoeba Paulinella chromatophora, which harbours independently acquired cyanobacterial endosymbionts functioning as plastids. Sequencing of the Paulinella endosymbiont genome revealed an absence of essential genes for protein trafficking, suggesting their residence in the host nucleus and import of protein products back into the endosymbiont. To investigate this hypothesis, we searched the Paulinella endosymbiont genome for homologues of higher plant translocon proteins that form the import apparatus in two-membrane envelopes of primary plastids. We found homologues of Toc12, Tic21 and Tic32, but genes for other key translocon proteins (e.g. Omp85/Toc75 and Tic20) were missing. We propose that these missing genes were transferred to the Paulinella nucleus and their products are imported and integrated into the endosymbiont envelope membranes, thereby creating an effective protein import apparatus. We further suggest that other bacterial/cyanobacterial endosymbionts found in protists, plants and animals could have evolved efficient protein import systems independently and, therefore, reached the status of true cellular organelles.
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Affiliation(s)
- A Bodył
- Department of Biodiversity and Evolutionary Taxonomy, Zoological Institute, University of Wrocław, Wrocław, Poland.
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139
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Shimoni-Shor E, Hassidim M, Yuval-Naeh N, Keren N. Disruption of Nap14, a plastid-localized non-intrinsic ABC protein in Arabidopsis thaliana results in the over-accumulation of transition metals and in aberrant chloroplast structures. PLANT, CELL & ENVIRONMENT 2010; 33:1029-38. [PMID: 20132520 DOI: 10.1111/j.1365-3040.2010.02124.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Chloroplasts are the major sink for Fe in shoot tissues because of the requirements of the photosynthetic process and to storage in ferritins. Such requirements are common both to plastids and to their evolutionary progenitors, the cyanobacteria. Here, we examined whether iron transport mechanisms were conserved throughout the evolution of photosynthetic organisms. Comparison of the sequences of putative plastid transporters from Arabidopsis thaliana with those involved in cyanobacterial Fe transport identified two orthologs of the FutC protein, AtNAP11 and AtNAP14. To study their function, we analysed insertional mutants in the genes coding for these proteins. Both nap11/nap11 and nap14/nap14 plants exhibited severe growth defects. Significant changes in transition metal homeostasis were detected only in nap14/nap14. This mutant was found to contain approximately 18 times more Fe in the shoot tissue than in wild-type plants. The increased shoot transition metal content was accompanied by a specific loss of chloroplast structures and by a reduction in transcript levels of Fe homeostasis-related genes. Based on these results, we propose that AtNAP14 plays an important role in plastid transition metal homeostasis. One possibility is that AtNAP14 is part of a chloroplast transporter complex. Alternatively, AtNAP14 function may be in regulating transition metal homeostasis.
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Affiliation(s)
- Einav Shimoni-Shor
- Department of Plant and Environmental Sciences, the Alexander Silberman Institute of Life Sciences, Edmond Safra Campus, Givat Ram, Hebrew University of Jerusalem, Jerusalem, Israel
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140
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Wu H, Ji Y, Du J, Kong D, Liang H, Ling HQ. ClpC1, an ATP-dependent Clp protease in plastids, is involved in iron homeostasis in Arabidopsis leaves. ANNALS OF BOTANY 2010; 105:823-33. [PMID: 20382967 PMCID: PMC2859920 DOI: 10.1093/aob/mcq051] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
BACKGROUND AND AIMS Iron (Fe) is necessary for plant growth and development. Although it is well known that Fe deficiency causes chlorosis in plants, it remains unclear how the Fe homeostasis is regulated in mesophyll cells. The aim of this work was to identify a gene related to Fe homeostasis in leaves. METHODS A spontaneous mutant irm1, which revealed typical Fe-deficiency chlorosis, was found from Arabidopsis thaliana. Using map-based cloning, the gene responsible for the altered phenotype of irm1 was cloned. The expression of genes was analysed using northern blot hybridization and multiplex RT-PCR analysis. Further, GUS staining with transgenic promoter-GUS lines and transient expression of the fusion protein with GFP were used for detecting the expression pattern of the gene in different tissues and at different developmental stages, and for the subcelluar localization of the gene product. KEY RESULTS A point mutation from G to A at nucleotide 2317 of ClpC1 on chromosome V of Arabidopsis is responsible for the irm1 phenotype. The leaf chlorosis of the mutant irm1 and clpc1 (a T-DNA-inserted null mutant of ClpC1) could be converted to green by watering the soil with Fe solution. The expression intensity of ferric reductase FRO8 in irm1 and clpc1 was disordered (significantly higher than that of wild type). CONCLUSIONS The glycine residue at amino acid 773 of ClpC1 is essential for its functions. In addition to its known functions reported previously, ClpC1 is involved in leaf Fe homeostasis, presumably via chloroplast translocation of some nuclear-encoded proteins which function in Fe transport.
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Affiliation(s)
- Huilan Wu
- The State Key Laboratory of Plant Cell and Chromosome Engineering, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, China
| | - Yanyan Ji
- The State Key Laboratory of Plant Cell and Chromosome Engineering, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, China
| | - Juan Du
- The State Key Laboratory of Plant Cell and Chromosome Engineering, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, China
- Graduate School of the Chinese Academy of Sciences, Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Danyu Kong
- The State Key Laboratory of Plant Cell and Chromosome Engineering, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, China
- Graduate School of the Chinese Academy of Sciences, Yuquan Road, Shijingshan District, Beijing 100049, China
| | - Hui Liang
- The State Key Laboratory of Plant Cell and Chromosome Engineering, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, China
| | - Hong-Qing Ling
- The State Key Laboratory of Plant Cell and Chromosome Engineering, National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Datun Road, Chaoyang District, Beijing 100101, China
- For correspondence. E-mail
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141
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Cosentino C, Fischer-Schliebs E, Bertl A, Thiel G, Homann U. Na+/H+ antiporters are differentially regulated in response to NaCl stress in leaves and roots of Mesembryanthemum crystallinum. THE NEW PHYTOLOGIST 2010; 186:669-80. [PMID: 20298477 DOI: 10.1111/j.1469-8137.2010.03208.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Salinity tolerance in plants involves controlled Na(+) transport at the site of Na(+) accumulation and intracellular Na(+) compartmentation. The focus of this study was the identification and analysis of the expression of Na(+)/H(+) antiporters in response to NaCl stress in one particular plant, the facultative halophyte Mesembryanthemum crystallinum Na(+)/H(+) antiporters of M. crystallinum were cloned by RACE-PCR from total mRNA of leaf mesophyll cells. Functional complementation of Saccharomyces cerevisiae and Escherichia coli mutants was performed. The kinetics of changes in the expression of antiporters were quantified by real-time PCR in leaves and roots. Five Na(+)/H(+) antiporters (McSOS1, McNhaD, McNHX1, McNHX2 and McNHX3) were cloned, representing the entire set of these transporters in M. crystallinum. The functionality of McSOS1, McHX1 and McNhaD was demonstrated in complementation experiments. Quantitative analysis revealed a temporal correlation between salt accumulation and expression levels of genes in leaves, but not in roots, which was most pronounced for McNhaD. Results suggest a physiological role of McSOS1, McNhaD and McNHX1 in Na(+) compartmentation during plant adaptation to high salinity. The study also provides evidence for salt-induced expression and function of the Na(+)/H(+) antiporter McNhaD in chloroplasts and demonstrates that the chloroplast is one of the compartments involved in the response of cells to salt stress.
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Affiliation(s)
- Cristian Cosentino
- Institut für Botanik, Technische Universität Darmstadt, 64287 Darmstadt, Germany
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142
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Yang TJW, Lin WD, Schmidt W. Transcriptional profiling of the Arabidopsis iron deficiency response reveals conserved transition metal homeostasis networks. PLANT PHYSIOLOGY 2010; 152:2130-2141. [PMID: 20181752 DOI: 10.1104/pp109152728] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Iron (Fe) deficiency is counteracted by a suite of responses to ensure maintenance of vital processes for which Fe is essential. Here, we report on transcriptional changes upon Fe deficiency, investigated in two Arabidopsis (Arabidopsis thaliana) accessions, Columbia (Col-0) and C24. Functional modules of the Arabidopsis Fe deficiency syndrome were inferred from clustering of Fe-responsive genes according to their coexpression. It was found that the redistribution of transition metals is an integral part of the reduction-based response to Fe starvation. The differential expression of metal transporters under the control of the FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR appeared to reflect an anticipated reaction rather than a response to the actual change in metal distribution. In contrast, the regulation of the zinc transporters ZRT/IRT-LIKE PROTEIN2 (ZIP2), ZIP3, ZIP4, and ZIP9 was dependent on the cellular zinc level, and their regulation by Fe was a secondary effect. Cellular Fe homeostasis was found to be closely coupled to Fe-related processes in the plastids. Using clustered genes as bait in gene-fishing experiments, we were able to attribute potentially important roles for gene candidates that have no previously described function in the Fe deficiency response. These results demonstrate a conceptually novel and integrative view into the regulation and interactions that allow Arabidopsis to adapt to suboptimal Fe availability.
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Affiliation(s)
- Thomas J W Yang
- Institute of Plant and Microbial Biology, Academia Sinica, 115 Taipei, Taiwan
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143
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Yang TJ, Lin WD, Schmidt W. Transcriptional profiling of the Arabidopsis iron deficiency response reveals conserved transition metal homeostasis networks. PLANT PHYSIOLOGY 2010; 152:2130-41. [PMID: 20181752 PMCID: PMC2850031 DOI: 10.1104/pp.109.152728] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Accepted: 02/16/2010] [Indexed: 05/17/2023]
Abstract
Iron (Fe) deficiency is counteracted by a suite of responses to ensure maintenance of vital processes for which Fe is essential. Here, we report on transcriptional changes upon Fe deficiency, investigated in two Arabidopsis (Arabidopsis thaliana) accessions, Columbia (Col-0) and C24. Functional modules of the Arabidopsis Fe deficiency syndrome were inferred from clustering of Fe-responsive genes according to their coexpression. It was found that the redistribution of transition metals is an integral part of the reduction-based response to Fe starvation. The differential expression of metal transporters under the control of the FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR appeared to reflect an anticipated reaction rather than a response to the actual change in metal distribution. In contrast, the regulation of the zinc transporters ZRT/IRT-LIKE PROTEIN2 (ZIP2), ZIP3, ZIP4, and ZIP9 was dependent on the cellular zinc level, and their regulation by Fe was a secondary effect. Cellular Fe homeostasis was found to be closely coupled to Fe-related processes in the plastids. Using clustered genes as bait in gene-fishing experiments, we were able to attribute potentially important roles for gene candidates that have no previously described function in the Fe deficiency response. These results demonstrate a conceptually novel and integrative view into the regulation and interactions that allow Arabidopsis to adapt to suboptimal Fe availability.
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144
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Protein import into chloroplasts: the Tic complex and its regulation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:740-7. [PMID: 20100520 DOI: 10.1016/j.bbamcr.2010.01.015] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 01/11/2010] [Accepted: 01/13/2010] [Indexed: 11/24/2022]
Abstract
Chloroplasts like mitochondria were derived from an endosymbiontic event. Due to the massive gene transfer to the nucleus during endosymbiosis, only a limited number of chloroplastic proteins are still encoded for in the plastid genome. Most of the nuclear-encoded plastidic proteins are post-translationally translocated back to the chloroplast via the general import pathway through distinct outer and inner envelope membrane protein complexes, the Toc and Tic translocons (Translocon at the outer/inner envelope membrane of chloroplasts). Eight Tic subunits have been described so far, including two potential channel proteins (Tic110 and Tic20), the "motor complex" (Tic40 associated with the stromal chaperone Hsp93) and the "redox regulon" (Tic62, Tic55, and Tic32) involved in regulation of protein import via the metabolic redox status of the chloroplast. Regulation can additionally occur via thioredoxins (Tic110 and Tic55) or via the calcium/calmodulin network (Tic110 and Tic32). In this review we present the current knowledge about the Tic complex focusing on its regulation and addressing some still open questions.
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145
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Abstract
Plastids are a heterogeneous family of organelles found ubiquitously in plants and algal cells. Most prominent are the chloroplasts, which carry out such essential processes as photosynthesis and the biosynthesis of fatty acids as well as of amino acids. As mitochondria, chloroplasts are derived from a single endosymbiotic event. They are believed to have evolved from an ancient cyanobacterium, which was engulfed by an early eukaryotic ancestor. During evolution the plastid genome has been greatly reduced and most of the genes have been transferred to the host nucleus. Consequently, more than 98% of all plastid proteins are translated on cytosolic ribosomes. They have to be posttranslationally targeted to and imported into the organelle. Targeting is assisted by cytosolic proteins which interact with proteins destined for plastids and thereby keep them in an import competent state. After reaching the target organelle, many proteins have to conquer the barrier of the chloroplast outer and inner envelope. This process is mediated by complex molecular machines in the outer (Toc complex) and inner (Tic complex) envelope of chloroplasts, respectively. Most proteins destined for the compartments inside the chloroplast contain a cleavable N-terminal transit peptide, whereas most of the outer envelope components insert into the membrane without such a targeting peptide.
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Affiliation(s)
- Penelope Strittmatter
- Department Biologie I-Botanik, Ludwig-Maximilians-Universität, Planegg-Martinsried and Munich Center for Integrated Protein Science, CiPSM, Ludwig-Maximilians- Universität, Munich, Germany
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147
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Abstract
Most proteins in chloroplasts are encoded by the nuclear genome and synthesized as precursors with N-terminal targeting signals called transit peptides. Novel machinery has evolved to specifically import these proteins from the cytosol into chloroplasts. This machinery consists of more than a dozen components located in and around the chloroplast envelope, including a pair of GTPase receptors, a beta-barrel-type channel across the outer membrane, and an AAA(+)-type motor in the stroma. How individual components assemble into functional subcomplexes and the sequential steps of the translocation process are being mapped out. An increasing number of noncanonical import pathways, including a pathway with initial transport through the endomembrane system, is being revealed. Multiple levels of control on protein transport into chloroplasts have evolved, including the development of two receptor subfamilies, one for photosynthetic proteins and one for housekeeping proteins. The functions or expression levels of some translocon components are further adjusted according to plastid type, developmental stage, and metabolic conditions.
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Affiliation(s)
- Hsou-min Li
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
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148
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Boij P, Patel R, Garcia C, Jarvis P, Aronsson H. In vivo studies on the roles of Tic55-related proteins in chloroplast protein import in Arabidopsis thaliana. MOLECULAR PLANT 2009; 2:1397-1409. [PMID: 19995737 DOI: 10.1093/mp/ssp079] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The Tic55 (Translocon at the inner envelope membrane of chloroplasts, 55 kDa) protein was identified in pea as a putative regulator, possibly linking chloroplast protein import to the redox state of the photosynthetic machinery. Two Tic55 homologs have been proposed to exist in Arabidopsis: atTic55-II and AtPTC52 (Protochlorophyllide-dependent Translocon Component, 52 kDa; has also been called atTic55-IV). Our phylogenetic analysis shows that atTic55-II is an ortholog of psTic55 from pea (Pisum sativum), and that AtPTC52 is a more distant homolog of the two. AtPTC52 was included in this study to rule out possible functional links between the proteins in Arabidopsis. No detectable mutant phenotypes were found in two independent T-DNA knockout mutant plant lines for each Arabidopsis protein, when compared with wild-type: visible appearance, chlorophyll content, photosynthetic performance, and chloroplast protein import, for example, were all normal. Both wild-type and tic55-II mutant chloroplasts exhibited deficient protein import when treated with diethylpyrocarbonate, indicating that Tic55 is not the sole target of this reagent in relation to protein import. Furthermore, ptc52 mutant chloroplasts were not defective with respect to pPORA import, which was previously reported to involve PTC52 in barley. Thus, we conclude that atTic55-II and AtPTC52 are not strictly required for functional protein import in Arabidopsis.
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Affiliation(s)
- Patrik Boij
- Department of Plant and Environmental Sciences, University of Gothenburg, Box 461, SE-405 30 Gothenburg, Sweden
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Bodył A, Mackiewicz P, Stiller JW. Early steps in plastid evolution: current ideas and controversies. Bioessays 2009; 31:1219-32. [DOI: 10.1002/bies.200900073] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Affiliation(s)
- Joe Morrissey
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
| | - Mary Lou Guerinot
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
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