101
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Zhou ZS, Yang SN, Li H, Zhu CC, Liu ZP, Yang ZM. Molecular dissection of mercury-responsive transcriptome and sense/antisense genes in Medicago truncatula. JOURNAL OF HAZARDOUS MATERIALS 2013; 252-253:123-31. [PMID: 23500795 DOI: 10.1016/j.jhazmat.2013.02.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Revised: 02/04/2013] [Accepted: 02/11/2013] [Indexed: 05/21/2023]
Abstract
We described a newly developed approach, namely next-generation tag sequencing, to identify global gene transcripts and complexity regulated by heavy metals in Medicago truncatula. Two cDNA libraries were generated from M. truncatula seedlings: treated and non-treated with the toxic heavy metal mercury Hg(II). With the large number of read-mapped genes generated, we observed that most of the genes were differentially expressed between the two libraries. In addition, several classes of new transcripts including transcription factors, antisense transcripts, and stress responsive genes were detected. The forty genes most altered in expression levels were associated with tolerance to environmental stress and secondary metabolism. Validation of genes by quantitative RT-PCR confirmed the results from deep-sequencing. Most of genes coding for metal transporters, sulfate metabolism, and cell wall solidification were significantly altered by Hg exposure. We also examined altered expression ratios of sense and antisense (S-AS) transcripts between the two libraries. By analyzing strand-specific information of read sequences, S-AS transcripts were found to be enriched with metal treatment. The transcriptome sequences were analyzed further with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) and showed diverse biological functions and metabolic pathways under the metal stress.
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Affiliation(s)
- Zhao Sheng Zhou
- Jiangsu Province Key Laboratory of Marine Biology, College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing, China
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102
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Song XQ, Liu LF, Jiang YJ, Zhang BC, Gao YP, Liu XL, Lin QS, Ling HQ, Zhou YH. Disruption of secondary wall cellulose biosynthesis alters cadmium translocation and tolerance in rice plants. MOLECULAR PLANT 2013; 6:768-80. [PMID: 23376772 DOI: 10.1093/mp/sst025] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Tricheary elements (TEs), wrapped by secondary cell wall, play essential roles in water, mineral, and nutrient transduction. Cadmium (Cd) is a toxic heavy metal that is absorbed by roots and transported to shoot, leaves, and grains through vascular systems in plants. As rice is a major source of Cd intake, many efforts have been made to establish 'low-Cd rice'. However, no links have been found between cellulose biosynthesis and cadmium accumulation. We report here a rice brittle culm13 mutant, resulting from a novel missense mutation (E101K) [corrected] in the N-terminus of cellulose synthase subunit 9 (CESA9). Except for the abnormal mechanical strength, the mutant plants are morphologically indistinguishable from the wild-type plants. Transmission electron microscopy (TEM) and chemical analyses showed a slight reduction in secondary wall thickness and 22% decrease in cellulose content in bc13 plants. Moreover, this mutation unexpectedly confers the mutant plants Cd tolerance due to less Cd accumulation in leaves. Expression analysis of the genes required for Cd uptake and transport revealed complicated alterations after applying Cd to wild-type and bc13. The mutants were further found to have altered vascular structure. More importantly, Cd concentration in the xylem saps from the bc13 plants was significantly lower than that from the wild-type. Combining the analyses of CESA9 gene expression and Cd content retention in the cell-wall residues, we conclude that CESA9(E101K) [corrected] mutation alters cell-wall properties in the conducting tissues, which consequently affects Cd translocation efficiency that largely contributes to the low Cd accumulation in the mutant plants.
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Affiliation(s)
- Xue-Qin Song
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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103
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Liu XM, Han HJ, Kim KE, Park HC, Hong JC, Yun DJ, Chung WS. WITHDRAWN: Overexpression of a C(2)H(2)-type zinc finger protein gene, ZAT11, leads to enhanced primary root growth and increased nickel ion sensitivity in Arabidopsis. Biochem Biophys Res Commun 2012:S0006-291X(12)02325-X. [PMID: 23228661 DOI: 10.1016/j.bbrc.2012.11.115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 11/29/2012] [Indexed: 11/25/2022]
Abstract
This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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Affiliation(s)
- Xiao-Min Liu
- Division of Applied Life Science (BK21 Program), Gyeongsang National University, Jinju 660-701, Republic of Korea
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104
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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: 120] [Impact Index Per Article: 10.0] [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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105
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Bhargava A, Carmona FF, Bhargava M, Srivastava S. Approaches for enhanced phytoextraction of heavy metals. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2012; 105:103-20. [PMID: 22542973 DOI: 10.1016/j.jenvman.2012.04.002] [Citation(s) in RCA: 192] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 03/20/2012] [Accepted: 04/01/2012] [Indexed: 05/20/2023]
Abstract
The contamination of the environment with toxic metals has become a worldwide problem. Metal toxicity affects crop yields, soil biomass and fertility. Soils polluted with heavy metals pose a serious health hazard to humans as well as plants and animals, and often requires soil remediation practices. Phytoextraction refers to the uptake of contaminants from soil or water by plant roots and their translocation to any harvestable plant part. Phytoextraction has the potential to remove contaminants and promote long-term cleanup of soil or wastewater. The success of phytoextraction as a potential environmental cleanup technology depends on factors like metal availability for uptake, as well as plants ability to absorb and accumulate metals in aerial parts. Efforts are ongoing to understand the genetics and biochemistry of metal uptake, transport and storage in hyperaccumulator plants so as to be able to develop transgenic plants with improved phytoremediation capability. Many plant species are being investigated to determine their usefulness for phytoextraction, especially high biomass crops. The present review aims to give an updated version of information available with respect to metal tolerance and accumulation mechanisms in plants, as well as on the environmental and genetic factors affecting heavy metal uptake. The genetic tools of classical breeding and genetic engineering have opened the door to creation of 'remediation' cultivars. An overview is presented on the possible strategies for developing novel genotypes with increased metal accumulation and tolerance to toxicity.
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Affiliation(s)
- Atul Bhargava
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow Campus, Gomti Nagar, Lucknow, UP, India.
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106
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Eudes A, George A, Mukerjee P, Kim JS, Pollet B, Benke PI, Yang F, Mitra P, Sun L, Cetinkol OP, Chabout S, Mouille G, Soubigou-Taconnat L, Balzergue S, Singh S, Holmes BM, Mukhopadhyay A, Keasling JD, Simmons BA, Lapierre C, Ralph J, Loqué D. Biosynthesis and incorporation of side-chain-truncated lignin monomers to reduce lignin polymerization and enhance saccharification. PLANT BIOTECHNOLOGY JOURNAL 2012; 10:609-20. [PMID: 22458713 DOI: 10.1111/j.1467-7652.2012.00692.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Lignocellulosic biomass is utilized as a renewable feedstock in various agro-industrial activities. Lignin is an aromatic, hydrophobic and mildly branched polymer integrally associated with polysaccharides within the biomass, which negatively affects their extraction and hydrolysis during industrial processing. Engineering the monomer composition of lignins offers an attractive option towards new lignins with reduced recalcitrance. The presented work describes a new strategy developed in Arabidopsis for the overproduction of rare lignin monomers to reduce lignin polymerization degree (DP). Biosynthesis of these 'DP reducers' is achieved by expressing a bacterial hydroxycinnamoyl-CoA hydratase-lyase (HCHL) in lignifying tissues of Arabidopsis inflorescence stems. HCHL cleaves the propanoid side-chain of hydroxycinnamoyl-CoA lignin precursors to produce the corresponding hydroxybenzaldehydes so that plant stems expressing HCHL accumulate in their cell wall higher amounts of hydroxybenzaldehyde and hydroxybenzoate derivatives. Engineered plants with intermediate HCHL activity levels show no reduction in total lignin, sugar content or biomass yield compared with wild-type plants. However, cell wall characterization of extract-free stems by thioacidolysis and by 2D-NMR revealed an increased amount of unusual C₆C₁ lignin monomers most likely linked with lignin as end-groups. Moreover the analysis of lignin isolated from these plants using size-exclusion chromatography revealed a reduced molecular weight. Furthermore, these engineered lines show saccharification improvement of pretreated stem cell walls. Therefore, we conclude that enhancing the biosynthesis and incorporation of C₆C₁ monomers ('DP reducers') into lignin polymers represents a promising strategy to reduce lignin DP and to decrease cell wall recalcitrance to enzymatic hydrolysis.
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Affiliation(s)
- Aymerick Eudes
- Joint BioEnergy Institute, EmeryStation East, Emeryville, CA, USA
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107
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Wu H, Chen C, Du J, Liu H, Cui Y, Zhang Y, He Y, Wang Y, Chu C, Feng Z, Li J, Ling HQ. Co-overexpression FIT with AtbHLH38 or AtbHLH39 in Arabidopsis-enhanced cadmium tolerance via increased cadmium sequestration in roots and improved iron homeostasis of shoots. PLANT PHYSIOLOGY 2012; 158:790-800. [PMID: 22184655 PMCID: PMC3271767 DOI: 10.1104/pp.111.190983] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Accepted: 12/16/2011] [Indexed: 05/18/2023]
Abstract
Cadmium (Cd) is toxic to plant cells. Under Cd exposure, the plant displayed leaf chlorosis, which is a typical symptom of iron (Fe) deficiency. Interactions of Cd with Fe have been reported. However, the molecular mechanisms of Cd-Fe interactions are not well understood. Here, we showed that FER-like Deficiency Induced Transcripition Factor (FIT), AtbHLH38, and AtbHLH39, three basic helix-loop-helix transcription factors involved in Fe homeostasis in plants, also play important roles in Cd tolerance. The gene expression analysis showed that the expression of FIT, AtbHLH38, and AtbHLH39 was up-regulated in the roots of plants treated with Cd. The plants overexpressing AtbHLH39 and double-overexpressing FIT/AtbHLH38 and FIT/AtbHLH39 exhibited more tolerance to Cd exposure than wild type, whereas no Cd tolerance was observed in plants overexpressing either AtbHLH38 or FIT. Further analysis revealed that co-overexpression of FIT with AtbHLH38 or AtbHLH39 constitutively activated the expression of Heavy Metal Associated3 (HMA3), Metal Tolerance Protein3 (MTP3), Iron Regulated Transporter2 (IRT2), and Iron Regulated Gene2 (IREG2), which are involved in the heavy metal detoxification in Arabidopsis (Arabidopis thaliana). Moreover, co-overexpression of FIT with AtbHLH38 or AtbHLH39 also enhanced the expression of NICOTIANAMINE SYNTHETASE1 (NAS1) and NAS2, resulting in the accumulation of nicotiananamine, a crucial chelator for Fe transportation and homeostasis. Finally, we showed that maintaining high Fe content in shoots under Cd exposure could alleviate the Cd toxicity. Our results provide new insight to understand the molecular mechanisms of Cd tolerance in plants.
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108
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Villiers F, Jourdain A, Bastien O, Leonhardt N, Fujioka S, Tichtincky G, Parcy F, Bourguignon J, Hugouvieux V. Evidence for functional interaction between brassinosteroids and cadmium response in Arabidopsis thaliana. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:1185-200. [PMID: 22131160 DOI: 10.1093/jxb/err335] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Plant hormones, in addition to regulating growth and development, are involved in biotic and abiotic stress responses. To investigate whether a hormone signalling pathway plays a role in the plant response to the heavy metal cadmium (Cd), gene expression data in response to eight hormone treatments were retrieved from the Genevestigator Arabidopsis thaliana database and compared with published microarray analysis performed on plants challenged with Cd. Across more than 3000 Cd-regulated genes, statistical approaches and cluster analyses highlighted that gene expression in response to Cd and brassinosteroids (BR) showed a significant similarity. Of note, over 75% of the genes showing consistent (e.g. opposite) regulation upon BR and Brz (BR biosynthesis inhibitor) exposure exhibited a BR-like response upon Cd exposure. This phenomenon was confirmed by qPCR analysis of the expression level of 10 BR-regulated genes in roots of Cd-treated wild-type (WT) plants. Although no change in BR content was observed in response to Cd in our experimental conditions, adding epibrassinolide (eBL, a synthetic brassinosteroid) to WT plants significantly enhanced Cd-induced root growth inhibition, highlighting a synergistic response between eBL and the metal. This effect was specific to this hormone treatment. On the other hand, dwarf1 seedlings, showing a reduced BR level, exhibited decreased root growth inhibition in response to Cd compared with WT, reversed by the addition of eBL. Similar results were obtained on Brz-treated WT plants. These results argue in favour of an interaction between Cd and BR signalling that modulates plant sensitivity, and opens new perspectives to understand the plant response to Cd.
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Affiliation(s)
- Florent Villiers
- CEA Laboratoire de Physiologie Cellulaire Végétale, UMR5168 Commissariat à l'Energie Atomique/CNRS/Université Joseph-Fourier/INRA, Institut de Recherches en Technologies et Sciences pour le Vivant, 17 rue des Martyrs, F-38054 Grenoble cedex 9, France
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109
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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: 641] [Impact Index Per Article: 53.4] [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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110
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Nishida S, Tsuzuki C, Kato A, Aisu A, Yoshida J, Mizuno T. AtIRT1, the primary iron uptake transporter in the root, mediates excess nickel accumulation in Arabidopsis thaliana. PLANT & CELL PHYSIOLOGY 2011; 52:1433-42. [PMID: 21742768 DOI: 10.1093/pcp/pcr089] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Nickel (Ni) is an essential nutrient for plants, but excessive amounts can be toxic. Ni competes with iron (Fe) in vivo, raising the possibility that Ni is competitively taken up via the Fe uptake system in plants. Here, we show evidence that AtIRT1, the primary Fe(2+) uptake transporter in the root, mediates Ni accumulation in Arabidopsis thaliana. In hydroponic cultures, excess Ni exposure increased Fe accumulation and the relative transcription level of AtIRT1 in roots, indicating that excess Ni induces AtIRT1 expression in roots. An Fe-deficient treatment increased Ni accumulation in plants, suggesting that excess Ni was absorbed via the Fe uptake system, which was induced by Fe starvation. Moreover, Ni accumulation under Fe-deficient conditions was markedly lower in AtIRT1-defective mutants than in the wild-type, Col-0. Furthermore, AtIRT1 showed Ni(2+) uptake activity in a yeast expression system. These data demonstrate that AtIRT1 transports Ni(2+) in roots, and strongly suggest that Ni accumulation is further accelerated by AtIRT1 that is expressed in response to excess Ni.
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Affiliation(s)
- Sho Nishida
- Graduate School of Bioresources, Mie University, Kurimamachiya-cho 1577, Tsu, Mie, 514-8507 Japan
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111
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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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112
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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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113
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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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114
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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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115
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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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116
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Lan P, Li W, Wen TN, Shiau JY, Wu YC, Lin W, Schmidt W. iTRAQ protein profile analysis of Arabidopsis roots reveals new aspects critical for iron homeostasis. PLANT PHYSIOLOGY 2011; 155:821-34. [PMID: 21173025 PMCID: PMC3032469 DOI: 10.1104/pp.110.169508] [Citation(s) in RCA: 120] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 12/15/2010] [Indexed: 05/17/2023]
Abstract
Iron (Fe) deficiency is a major constraint for plant growth and affects the quality of edible plant parts. To investigate the mechanisms underlying Fe homeostasis in plants, Fe deficiency-induced changes in the protein profile of Arabidopsis (Arabidopsis thaliana) roots were comprehensively analyzed using iTRAQ (Isobaric Tag for Relative and Absolute Quantification) differential liquid chromatography-tandem mass spectrometry on a LTQ-Orbitrap with high-energy collision dissociation. A total of 4,454 proteins were identified with a false discovery rate of less than 1.1%, and 2,882 were reliably quantified. A subset of 101 proteins was differentially expressed upon Fe deficiency. The changes in protein profiles upon Fe deficiency show low congruency with previously reported alterations in transcript levels, indicating posttranscriptional changes, and provide complementary information on Fe deficiency-induced processes. The abundance of proteins involved in the synthesis/regeneration of S-adenosylmethionine, the phenylpropanoid pathway, the response to oxidative stress, and respiration was highly increased by Fe deficiency. Using Fe-responsive proteins as bait, genome-wide fishing for partners with predictable or confirmed interologs revealed that RNA processing and ribonucleoprotein complex assembly may represent critical processes that contribute to the regulation of root responses to Fe deficiency, possibly by biasing translation efficiency.
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117
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Functional Classification of Plant Plasma Membrane Transporters. THE PLANT PLASMA MEMBRANE 2011. [DOI: 10.1007/978-3-642-13431-9_6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Long TA, Tsukagoshi H, Busch W, Lahner B, Salt DE, Benfey PN. The bHLH transcription factor POPEYE regulates response to iron deficiency in Arabidopsis roots. THE PLANT CELL 2010; 22:2219-36. [PMID: 20675571 PMCID: PMC2929094 DOI: 10.1105/tpc.110.074096] [Citation(s) in RCA: 415] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2010] [Revised: 06/21/2010] [Accepted: 07/13/2010] [Indexed: 05/17/2023]
Abstract
Global population increases and climate change underscore the need for better comprehension of how plants acquire and process nutrients such as iron. Using cell type-specific transcriptional profiling, we identified a pericycle-specific iron deficiency response and a bHLH transcription factor, POPEYE (PYE), that may play an important role in this response. Functional analysis of PYE suggests that it positively regulates growth and development under iron-deficient conditions. Chromatin immunoprecipitation-on-chip analysis and transcriptional profiling reveal that PYE helps maintain iron homeostasis by regulating the expression of known iron homeostasis genes and other genes involved in transcription, development, and stress response. PYE interacts with PYE homologs, including IAA-Leu Resistant3 (ILR3), another bHLH transcription factor that is involved in metal ion homeostasis. Moreover, ILR3 interacts with a third protein, BRUTUS (BTS), a putative E3 ligase protein, with metal ion binding and DNA binding domains, which negatively regulates the response to iron deficiency. PYE and BTS expression is also tightly coregulated. We propose that interactions among PYE, PYE homologs, and BTS are important for maintaining iron homeostasis under low iron conditions.
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Affiliation(s)
- Terri A. Long
- Department of Biology and Institute for Genome Science and Policy Center for Systems Biology, Duke University, Durham, North Carolina 27708
| | - Hironaka Tsukagoshi
- Department of Biology and Institute for Genome Science and Policy Center for Systems Biology, Duke University, Durham, North Carolina 27708
| | - Wolfgang Busch
- Department of Biology and Institute for Genome Science and Policy Center for Systems Biology, Duke University, Durham, North Carolina 27708
| | - Brett Lahner
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907
| | - David E. Salt
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907
| | - Philip N. Benfey
- Department of Biology and Institute for Genome Science and Policy Center for Systems Biology, Duke University, Durham, North Carolina 27708
- Address correspondence to
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120
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Saito A, Saito M, Ichikawa Y, Yoshiba M, Tadano T, Miwa E, Higuchi K. Difference in the distribution and speciation of cellular nickel between nickel-tolerant and non-tolerant Nicotiana tabacum L. cv. BY-2 cells. PLANT, CELL & ENVIRONMENT 2010; 33:174-87. [PMID: 19906154 DOI: 10.1111/j.1365-3040.2009.02068.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
To evaluate Ni dynamics at the subcellular level, the distribution and speciation of Ni were determined in wild-type (WT) and Ni-tolerant (NIT) tobacco BY-2 cell lines. When exposed to low but toxic levels of Ni, NIT cells were found to contain 2.5-fold more Ni (14% of whole-cell Ni values) in their cell walls than WT cells (6% of whole-cell Ni values). In addition to higher levels of Ni in the apoplast, a higher proportion (94%) of symplastic Ni was localized in the vacuoles of NIT cells than in the vacuoles of WT cells (81%). The concentration of cytosolic Ni in the NIT cells was significantly lower (18 nmol g(-1) FW) than that in the WT cells (85 nmol g(-1) FW). In silico simulation showed that 95% of vacuolar Ni was in the form of Ni-citrate complexes, and that free Ni(2+) was virtually absent in the NIT cells. On the other hand, the amount of free metal ions was markedly increased in WT cells because free citrate was depleted by chelation of Ni. A protoplast viability assay using BCECF-AM further demonstrated that the main mechanism that confers strong Ni tolerance was present in the symplast as opposed to the cell wall.
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Affiliation(s)
- Akihiro Saito
- Laboratory of Plant Production Chemistry, Department of Applied Biology and Chemistry, Tokyo University of Agriculture, Tokyo 156-8502, Japan
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121
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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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122
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Conte S, Stevenson D, Furner I, Lloyd A. Multiple antibiotic resistance in Arabidopsis is conferred by mutations in a chloroplast-localized transport protein. PLANT PHYSIOLOGY 2009; 151:559-73. [PMID: 19675150 PMCID: PMC2754617 DOI: 10.1104/pp.109.143487] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Accepted: 08/07/2009] [Indexed: 05/18/2023]
Abstract
Widespread antibiotic resistance is a major public health concern, and plants represent an emerging antibiotic exposure route. Recent studies indicate that crop plants fertilized with antibiotic-laden animal manure accumulate antibiotics; however, the molecular mechanisms of antibiotic entry and subcellular partitioning within plant cells remain unknown. Here, we report that mutations in the Arabidopsis (Arabidopsis thaliana) locus Multiple Antibiotic Resistance1 (MAR1) confer resistance, while MAR1 overexpression causes hypersensitivity to multiple aminoglycoside antibiotics. Additionally, yeast expressing MAR1 are hypersensitive to the aminoglycoside G418. MAR1 encodes a protein with 11 putative transmembrane domains with low similarity to ferroportin1 from Danio rerio. A MAR1:yellow fluorescent protein fusion localizes to the chloroplast, and chloroplasts from plants overexpressing MAR1 accumulate more of the aminoglycoside gentamicin, while mar1-1 mutant chloroplasts accumulate less than the wild type. MAR1 overexpression lines are slightly chlorotic, and chlorosis is rescued by exogenous iron. MAR1 expression is also down-regulated by low iron. These data suggest that MAR1 is a plastid transporter that is likely to be involved in cellular iron homeostasis and allows opportunistic entry of multiple antibiotics into the chloroplast.
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Affiliation(s)
- Sarah Conte
- Section of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712, USA.
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123
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Morrissey J, Guerinot ML. Iron uptake and transport in plants: the good, the bad, and the ionome. Chem Rev 2009; 109:4553-67. [PMID: 19754138 PMCID: PMC2764373 DOI: 10.1021/cr900112r] [Citation(s) in RCA: 265] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Joe Morrissey
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
| | - Mary Lou Guerinot
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
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Morrissey J, Baxter IR, Lee J, Li L, Lahner B, Grotz N, Kaplan J, Salt DE, Guerinot ML. The ferroportin metal efflux proteins function in iron and cobalt homeostasis in Arabidopsis. THE PLANT CELL 2009; 21:3326-38. [PMID: 19861554 PMCID: PMC2782287 DOI: 10.1105/tpc.109.069401] [Citation(s) in RCA: 195] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 09/15/2009] [Accepted: 10/08/2009] [Indexed: 05/18/2023]
Abstract
Relatively little is known about how metals such as iron are effluxed from cells, a necessary step for transport from the root to the shoot. Ferroportin (FPN) is the sole iron efflux transporter identified to date in animals, and there are two closely related orthologs in Arabidopsis thaliana, IRON REGULATED1 (IREG1/FPN1) and IREG2/FPN2. FPN1 localizes to the plasma membrane and is expressed in the stele, suggesting a role in vascular loading; FPN2 localizes to the vacuole and is expressed in the two outermost layers of the root in response to iron deficiency, suggesting a role in buffering metal influx. Consistent with these roles, fpn2 has a diminished iron deficiency response, whereas fpn1 fpn2 has an elevated iron deficiency response. Ferroportins also play a role in cobalt homeostasis; a survey of Arabidopsis accessions for ionomic phenotypes showed that truncation of FPN2 results in elevated shoot cobalt levels and leads to increased sensitivity to the metal. Conversely, loss of FPN1 abolishes shoot cobalt accumulation, even in the cobalt accumulating mutant frd3. Consequently, in the fpn1 fpn2 double mutant, cobalt cannot move to the shoot via FPN1 and is not sequestered in the root vacuoles via FPN2; instead, cobalt likely accumulates in the root cytoplasm causing fpn1 fpn2 to be even more sensitive to cobalt than fpn2 mutants.
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Affiliation(s)
- Joe Morrissey
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
| | - Ivan R. Baxter
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907
| | - Joohyun Lee
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
| | - Liangtao Li
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84132
| | - Brett Lahner
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907
| | - Natasha Grotz
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
| | - Jerry Kaplan
- Department of Pathology, University of Utah School of Medicine, Salt Lake City, Utah 84132
| | - David E. Salt
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907
- Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907
| | - Mary Lou Guerinot
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755
- Address correspondence to
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125
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Tejada-Jiménez M, Galván A, Fernández E, Llamas A. Homeostasis of the micronutrients Ni, Mo and Cl with specific biochemical functions. CURRENT OPINION IN PLANT BIOLOGY 2009; 12:358-363. [PMID: 19487155 DOI: 10.1016/j.pbi.2009.04.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 04/27/2009] [Accepted: 04/27/2009] [Indexed: 05/27/2023]
Abstract
Homeostasis of three elements nickel, molybdenum and chloride is analysed. These micronutrients, at amounts varying in orders of magnitude, fulfil important cell functions. In general terms, cells use similar strategies to ensure that the elements are within physiological ranges avoiding high toxic concentrations. These strategies correspond to specific carriers, channels and pumps, intermediate steps (chelating/sequestration/binding/metabolic conversion/storage), final steps related to specific enzyme functionality and putative sensing proteins. Single cell homeostasis, coordinated with an efficient redistribution by xylem loading, ensures in turn homeostasis at the whole plant level. Recent advances are based on the molecular identification of some key components.
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Affiliation(s)
- Manuel Tejada-Jiménez
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias, Universidad de Córdoba, Campus de Rabanales, Córdoba, Spain
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126
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Mizuno T, Horie K, Nosaka S, Obata H, Mizuno N. Serpentine Plants in Hokkaido and their Chemical Characteristics. Northeast Nat (Steuben) 2009. [DOI: 10.1656/045.016.0506] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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127
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Buckhout TJ, Yang TJW, Schmidt W. Early iron-deficiency-induced transcriptional changes in Arabidopsis roots as revealed by microarray analyses. BMC Genomics 2009; 10:147. [PMID: 19348669 PMCID: PMC2676303 DOI: 10.1186/1471-2164-10-147] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Accepted: 04/06/2009] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Iron (Fe) is an essential nutrient in plants and animals, and Fe deficiency results in decreased vitality and performance. Due to limited bio-availability of Fe, plants have evolved sophisticated adaptive alterations in development, biochemistry and metabolism that are mainly regulated at the transcriptional level. We have investigated the early transcriptional response to Fe deficiency in roots of the model plant Arabidopsis, using a hydroponic system that permitted removal of Fe from the nutrient solution within seconds and transferring large numbers of plants with little or no mechanical damage to the root systems. We feel that this experimental approach offers significant advantages over previous and recent DNA microarray investigations of the Fe-deficiency response by increasing the resolution of the temporal response and by decreasing non-Fe deficiency-induced transcriptional changes, which are common in microarray analyses. RESULTS The expression of sixty genes were changed after 6 h of Fe deficiency and 65% of these were found to overlap with a group of seventy-nine genes that were altered after 24 h. A disproportionally high number of transcripts encoding ion transport proteins were found, which function to increase the Fe concentration and decrease the zinc (Zn) concentration in the cytosol. Analysis of global changes in gene expression revealed that changes in Fe availability were associated with the differential expression of genes that encode transporters with presumed function in uptake and distribution of transition metals other than Fe. It appeared that under conditions of Fe deficiency, the capacity for Zn uptake increased, most probably the result of low specificity of the Fe transporter IRT1 that was induced upon Fe deficiency. The transcriptional regulation of several Zn transports under Fe deficiency led presumably to the homeostatic regulation of the cytosolic concentration of Zn and of other transition metal ions such as Mn to avoid toxicity. CONCLUSION The genomic information obtained from this study gives insights into the rapid transcriptional responses to Fe shortage in plants, and is important for understanding how changes in nutrient availability are translated into responses that help to avoid imbalances in ion distribution. We further identified rapidly induced or repressed genes with potential roles in perception and signaling during Fe deficiency which may aid in the elucidation of these processes.
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Affiliation(s)
- Thomas J Buckhout
- Institute of Plant and Microbial Biology, Academia Sinica, 115 Taipei, Taiwan.
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Chapter 3. New insights into plant vacuolar structure and dynamics. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 277:103-35. [PMID: 19766968 DOI: 10.1016/s1937-6448(09)77003-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The plant vacuole is a multifunctional organelle and is essential for plant development and growth. The most distinctive feature of the plant vacuole is its size, which usually occupies over 80-90% of the cell volume in well-developed somatic cells, and is therefore highly involved in cell growth and plant body size. Recent progress in the visualization of the vacuole, together with developments in image analysis, has revealed the highly organized and complex morphology of the vacuole, as well as its dynamics. The plant vacuolar membrane (VM) forms not only a typically large vacuole but also other structures, such as tubular structures, transvacuolar strands, bulbs, and sheets. In higher plant cells, actin microfilaments are mainly located near the VM and are involved in vacuolar shape changes with the actin-myosin systems. Most recently, microtubule-dependent regulation of vacuolar structures in moss plant cells was reported, suggesting a diversity of mechanisms regulating vacuolar morphogenesis.
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129
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Ingle RA, Fricker MD, Smith JAC. Evidence for nickel/proton antiport activity at the tonoplast of the hyperaccumulator plant Alyssum lesbiacum. PLANT BIOLOGY (STUTTGART, GERMANY) 2008; 10:746-753. [PMID: 18950432 DOI: 10.1111/j.1438-8677.2008.00080.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The mechanism of nickel uptake into vacuoles isolated from leaf tissue of Alyssum lesbiacum was investigated to help understand the ability of this species to hyperaccumulate Ni. An imaging system was designed to monitor Ni uptake by single vacuoles using the metal-sensitive fluorescent dye, Newport Green. Nickel uptake into isolated vacuoles from leaf tissue of A. lesbiacum was enhanced by the presence of Mg/ATP, presumably via energisation of the vacuolar H(+)-ATPase (V-ATPase). This ATP-stimulated Ni uptake was abolished by bafilomycin (a diagnostic inhibitor of the V-ATPase) and by dissipation of the transmembrane pH difference with an uncoupler. These observations are consistent with Ni(2+)/nH(+) antiport activity at the tonoplast driven by a proton electrochemical gradient established by the V-ATPase, which would provide a mechanism for secondary active transport of Ni(2+) into the vacuole. This study provides insights into the molecular basis of Ni tolerance in Alyssum, and may aid in the identification of genes involved in Ni hyperaccumulation.
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Affiliation(s)
- R A Ingle
- Department of Molecular and Cell Biology, University of Cape Town, Rondebosch, South Africa.
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130
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Kim SA, Guerinot ML. Mining iron: iron uptake and transport in plants. FEBS Lett 2007; 581:2273-80. [PMID: 17485078 DOI: 10.1016/j.febslet.2007.04.043] [Citation(s) in RCA: 221] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Accepted: 04/18/2007] [Indexed: 10/23/2022]
Abstract
Iron uptake in plants is highly regulated in order to supply amounts sufficient for optimal growth while preventing excess accumulation. In response to iron deficiency, plants induce either reduction-based or chelation-based mechanisms to enhance iron uptake from the soil. Genes involved in each mechanism have been identified from various model plants including Arabidopsis and rice. Iron transport within plants is also tightly controlled. New information has emerged on transporters that play a role in xylem loading and phloem loading/unloading of iron, and on the iron chelators involved in iron homeostasis. Some of the components regulating iron deficiency responses also have been elucidated, demonstrating that iron dependent gene regulation occurs at both the transcriptional and post-transcriptional levels.
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Affiliation(s)
- Sun A Kim
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA
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131
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Krämer U, Talke IN, Hanikenne M. Transition metal transport. FEBS Lett 2007; 581:2263-72. [PMID: 17462635 DOI: 10.1016/j.febslet.2007.04.010] [Citation(s) in RCA: 272] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 04/02/2007] [Accepted: 04/03/2007] [Indexed: 11/26/2022]
Abstract
Transition metal transporters are of central importance in the plant metal homeostasis network which maintains internal metal concentrations within physiological limits. An overview is given of the functions of known transition metal transporters in the context of the unique chemical properties of their substrates. The modifications of the metal homeostasis network associated with the adaptation to an extreme metalliferous environment are illustrated in two Brassicaceae metal hyperaccumulator model plants based on cross-species transcriptomics studies. In a comparison between higher plants and unicellular algae, hypotheses are generated for evolutionary changes in metal transporter complements associated with the transition to multicellularity.
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Affiliation(s)
- Ute Krämer
- Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, D-14476, Potsdam/Golm, Germany.
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