86 results on '"Ryan, Peter R."'
Search Results
2. ZmMATE6 from maize encodes a citrate transporter that enhances aluminum tolerance in transgenic Arabidopsis thaliana.
- Author
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Du H, Ryan PR, Liu C, Li H, Hu W, Yan W, Huang Y, He W, Luo B, Zhang X, Gao S, Zhou S, and Zhang S
- Subjects
- Arabidopsis physiology, Carrier Proteins physiology, Crops, Agricultural genetics, Crops, Agricultural physiology, Genes, Plant, Genetic Variation, Genotype, Plant Roots metabolism, Plants, Genetically Modified genetics, Plants, Genetically Modified physiology, Sequence Analysis, Protein, Zea mays physiology, Adaptation, Physiological genetics, Adaptation, Physiological physiology, Aluminum adverse effects, Arabidopsis genetics, Carrier Proteins genetics, Gene Expression Regulation, Plant drug effects, Zea mays genetics
- Abstract
The yields of cereal crops grown on acidic soils are often reduced by aluminum (Al) toxicity because the prevalence of toxic Al
3+ cations increases as pH falls below 5.0. The Al-dependent release of citrate from resistant lines of maize is controlled by ZmMATE1 which encodes a multidrug and toxic compound extrusion (MATE) transporter protein. ZmMATE6 is another member of this family in maize whose expression is also increased by Al treatment. We investigated the function of this gene in more detail to determine whether it also contributes to Al resistance. Quantitative RT-PCR measurements found that ZmMATE6 was expressed in the roots and leaves of Al-resistant and sensitive inbred lines. Treatment with Al induced ZmMATE6 expression in all tissues but several other divalent or trivalent cations tested had no effect on expression. This expression pattern and the induction by Al treatment was confirmed in ZmMATE6 promoter-β-glucuronidase fusion lines. Heterogeneous expression of ZmMATE6 displayed a greater Al-activated release of citrate from the roots and was significantly resistant to Al toxicity than controls. This was associated with reduced accumulation of Al in the root tissues. Our results demonstrated that ZmMATE6 expression is induced by Al and functions as a citrate transporter., (Copyright © 2021. Published by Elsevier B.V.)- Published
- 2021
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3. The role of transposable elements in the evolution of aluminium resistance in plants.
- Author
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Pereira JF and Ryan PR
- Subjects
- DNA, Plant metabolism, Drug Resistance genetics, Evolution, Molecular, Plant Proteins genetics, Plant Proteins metabolism, Plants drug effects, Plants metabolism, Aluminum adverse effects, DNA Transposable Elements genetics, DNA, Plant genetics, Gene Expression Regulation, Plant drug effects, Plants genetics, Soil Pollutants adverse effects
- Abstract
Aluminium (Al) toxicity can severely reduce root growth and consequently affect plant development and yield. A mechanism by which many species resist the toxic effects of Al relies on the efflux of organic anions (OAs) from the root apices via OA transporters. Several of the genes encoding these OA transporters contain transposable elements (TEs) in the coding sequences or in flanking regions. Some of the TE-induced mutations impact Al resistance by modifying the level and/or location of gene expression so that OA efflux from the roots is increased. The importance of genomic modifications for improving the adaptation of plants to acid soils has been raised previously, but the growing number of examples linking TEs with these changes requires highlighting. Here, we review the role of TEs in creating genetic modifications that enhance the adaptation of plants to acid soils by increasing the release of OAs from the root apices. We argue that TEs have been an important source of beneficial mutations that have co-opted OA transporter proteins with other functions to perform this role. These changes have occurred relatively recently in the evolution of many species and likely facilitated their expansion into regions with acidic soils.
- Published
- 2019
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4. A chimeric protein of aluminum-activated malate transporter generated from wheat and Arabidopsis shows enhanced response to trivalent cations.
- Author
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Sasaki T, Tsuchiya Y, Ariyoshi M, Ryan PR, and Yamamoto Y
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- Animals, Arabidopsis drug effects, Arabidopsis genetics, Arabidopsis Proteins agonists, Arabidopsis Proteins antagonists & inhibitors, Arabidopsis Proteins genetics, Biological Transport drug effects, Cells, Cultured, Erbium pharmacology, Gadolinium pharmacology, Gene Expression, Kinetics, Lanthanum pharmacology, Oocytes cytology, Oocytes drug effects, Oocytes metabolism, Organic Anion Transporters agonists, Organic Anion Transporters antagonists & inhibitors, Organic Anion Transporters genetics, Plant Cells drug effects, Plant Cells metabolism, Recombinant Fusion Proteins genetics, Nicotiana genetics, Nicotiana metabolism, Triticum drug effects, Triticum genetics, Xenopus laevis, Ytterbium pharmacology, Aluminum pharmacology, Arabidopsis metabolism, Arabidopsis Proteins metabolism, Malates metabolism, Organic Anion Transporters metabolism, Recombinant Fusion Proteins metabolism, Triticum metabolism
- Abstract
TaALMT1 from wheat (Triticum aestivum) and AtALMT1 from Arabidopsis thaliana encode aluminum (Al)-activated malate transporters, which confer acid-soil tolerance by releasing malate from roots. Chimeric proteins from TaALMT1 and AtALMT1 (Ta::At, At::Ta) were previously analyzed in Xenopus laevis oocytes. Those studies showed that Al could activate malate efflux from the Ta::At chimera but not from At::Ta. Here, functions of TaALMT1, AtALMT1 and the chimeric protein Ta::At were compared in cultured tobacco BY-2 cells. We focused on the sensitivity and specificity of their activation by trivalent cations. The activation of malate efflux by Al was at least two-fold greater in the chimera than the native proteins. All proteins were also activated by lanthanides (erbium, ytterbium, gadolinium, and lanthanum), but the chimera again released more malate than TaALMT1 or AtALMT1. In Xenopus oocytes, Al, ytterbium, and erbium activated inward currents from the native TaALMT1 and the chimeric protein, but gadolinium only activated currents from the chimera. Lanthanum inhibited currents from both proteins. These results demonstrated that function of the chimera protein was altered compared to the native proteins and was more responsive to a range of trivalent cations when expressed in plant cells., (Copyright © 2016 Elsevier B.V. All rights reserved.)
- Published
- 2016
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5. Introgression of genes from bread wheat enhances the aluminium tolerance of durum wheat.
- Author
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Han C, Zhang P, Ryan PR, Rathjen TM, Yan Z, and Delhaize E
- Subjects
- Chromosome Mapping, Chromosomes, Plant, Plant Breeding, Plant Proteins genetics, Polyploidy, Soil chemistry, Triticum drug effects, Aluminum chemistry, Crosses, Genetic, Genes, Plant, Organic Anion Transporters genetics, Triticum genetics
- Abstract
Key Message: The aluminium tolerance of durum wheat was markedly enhanced by introgression of TaALMT1 and TaMATE1B from bread wheat. In contrast to bread wheat, TaMATE1B conferred greater aluminium tolerance than TaALMT1. Durum wheat (tetraploid AABB, Triticum turgidum) is a species that grows poorly on acid soils due to its sensitivity of Al(3+). By contrast, bread wheat (hexaploid AABBDD, T. aestivum) shows a large variation in Al(3+) tolerance which can be attributed to a major gene (TaALMT1) located on chromosome 4D as well as to other genes of minor effect such as TaMATE1B. Genotypic variation for Al(3+) tolerance in durum germplasm is small and the introgression of genes from bread wheat is one option for enhancing the ability of durum wheat to grow on acid soils. Introgression of a large fragment of the 4D chromosome previously increased the Al(3+) tolerance of durum wheat demonstrating the viability of transferring the TaALMT1 gene to durum wheat to increase its Al(3+) tolerance. Here, we used a ph1 (pairing homoeologous) mutant of durum wheat to introgress a small fragment of the 4D chromosome harboring the TaALMT1 gene. The size of the 4D chromosomal fragment introgressed into durum wheat was estimated by markers, fluorescence in situ hybridisation and real-time quantitative PCR. In a parallel strategy, we introgressed TaMATE1B from bread wheat into durum wheat using conventional crosses. Both genes separately increased the Al(3+) tolerance of durum wheat in both hydroponics and soil cultures. In contrast to bread wheat, the TaMATE1B gene was more effective than TaALMT1 in increasing the Al(3+) tolerance of durum wheat grown on acid soil.
- Published
- 2016
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6. A new allele for aluminium tolerance gene in barley (Hordeum vulgare L.).
- Author
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Ma Y, Li C, Ryan PR, Shabala S, You J, Liu J, Liu C, and Zhou M
- Subjects
- 5' Untranslated Regions, Citric Acid metabolism, DNA Transposable Elements, DNA, Plant genetics, Gene Expression Regulation, Plant, Genotype, Hordeum drug effects, Malates metabolism, Plant Roots drug effects, Plant Roots metabolism, Quantitative Trait Loci, Sequence Analysis, DNA, Alleles, Aluminum toxicity, Hordeum genetics, Plant Proteins genetics
- Abstract
Background: Aluminium (Al) toxicity is the main factor limiting the crop production in acid soils and barley (Hordeum vulgare L.) is one of the most Al-sensitive of the small-grained cereals. The major gene for Al tolerance in barley is HvAACT1 (HvMATE) on chromosome 4H which encodes a multidrug and toxic compound extrusion (MATE) protein. The HvAACT1 protein facilitates the Al-activated release of citrate from root apices which protects the growing cells and enables root elongation to continue. A 1 kb transposable element-like insert in the 5' untranslated region (UTR) of HvAACT1 is associated with increased gene expression and tolerance and a PCR-based marker is available to score for this insertion., Results: We screened a wide range of barley genotypes for Al tolerance and identified a moderately tolerant Chinese genotype named CXHKSL which did not show the typical allele in the 5' UTR of HvAACT1 associated with tolerance. We investigated the mechanism of Al tolerance in CXHKSL and concluded it also relies on the Al-activated release of citrate from roots. Quantitative trait loci (QTL) analysis of double haploid lines generated with CXHKSL and the Al-sensitive variety Gairdner mapped the tolerance locus to the same region as HvAACT1 on chromosome 4H., Conclusions: Our results show that the Chinese barley genotype CXHKSL possesses a novel allele of the major Al tolerance gene HvAACT1.
- Published
- 2016
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7. Transgenic Arabidopsis thaliana plants expressing a β-1,3-glucanase from sweet sorghum (Sorghum bicolor L.) show reduced callose deposition and increased tolerance to aluminium toxicity.
- Author
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Zhang H, Shi WL, You JF, Bian MD, Qin XM, Yu H, Liu Q, Ryan PR, and Yang ZM
- Subjects
- Aluminum analysis, Arabidopsis drug effects, Arabidopsis enzymology, Arabidopsis physiology, Glucan 1,3-beta-Glucosidase physiology, Glucans analysis, Glucans physiology, Plant Roots chemistry, Plant Roots physiology, Plants, Genetically Modified drug effects, Plants, Genetically Modified enzymology, Plants, Genetically Modified physiology, Real-Time Polymerase Chain Reaction, Sorghum drug effects, Sorghum enzymology, Sorghum physiology, Aluminum toxicity, Arabidopsis metabolism, Glucan 1,3-beta-Glucosidase metabolism, Glucans metabolism, Plants, Genetically Modified metabolism, Sorghum metabolism
- Abstract
Seventy-one cultivars of sweet sorghum (Sorghum bicolor L.) were screened for aluminium (Al) tolerance by measuring relative root growth (RRG). Two contrasting cultivars, ROMA (Al tolerant) and POTCHETSTRM (Al sensitive), were selected to study shorter term responses to Al stress. POTCHETSTRM had higher callose synthase activity, lower β-1,3-glucanase activity and more callose deposition in the root apices during Al treatment compared with ROMA. We monitored the expression of 12 genes involved in callose synthesis and degradation and found that one of these, SbGlu1 (Sb03g045630.1), which encodes a β-1,3-glucanase enzyme, best explained the contrasting deposition of callose in ROMA and POTCHETSTRM during Al treatment. Full-length cDNAs of SbGlu1 was prepared from ROMA and POTCHETSTRM and expressed in Arabidopsis thaliana using the constitutive cauliflower mosaic virus (CaMV) 35S promoter. Independent transgenic lines displayed significantly greater Al tolerance than wild-type plants and vector-only controls. This phenotype was associated with greater total β-1,3-glucanase activity, less Al accumulation and reduced callose deposition in the roots. These results suggest that callose production is not just an early indicator of Al stress in plants but likely to be part of the toxicity pathway that leads to the inhibition of root growth., (© 2014 John Wiley & Sons Ltd.)
- Published
- 2015
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8. A domain-based approach for analyzing the function of aluminum-activated malate transporters from wheat (Triticum aestivum) and Arabidopsis thaliana in Xenopus oocytes.
- Author
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Sasaki T, Tsuchiya Y, Ariyoshi M, Ryan PR, Furuichi T, and Yamamoto Y
- Subjects
- Amino Acid Sequence, Animals, Arabidopsis drug effects, Arabidopsis genetics, Arabidopsis Proteins genetics, Biological Transport, Female, Molecular Sequence Data, Oocytes, Organic Anion Transporters genetics, Plant Proteins genetics, Plant Proteins metabolism, Plant Roots genetics, Protein Structure, Tertiary, Recombinant Proteins, Sequence Alignment, Sequence Deletion, Triticum drug effects, Triticum genetics, Xenopus, Aluminum pharmacology, Arabidopsis physiology, Arabidopsis Proteins metabolism, Malates metabolism, Organic Anion Transporters metabolism, Triticum physiology
- Abstract
Wheat and Arabidopsis plants respond to aluminum (Al) ions by releasing malate from their root apices via Al-activated malate transporter. Malate anions bind with the toxic Al ions and contribute to the Al tolerance of these species. The genes encoding the transporters in wheat and Arabidopsis, TaALMT1 and AtALMT1, respectively, were expressed in Xenopus laevis oocytes and characterized electrophysiologically using the two-electrode voltage clamp system. The Al-activated currents generated by malate efflux were detected for TaALMT1 but not for AtALMT1. Chimeric proteins were generated by swapping the N- and C-terminal halves of TaALMT1 and AtALMT1 (Ta::At and At::Ta). When these chimeras were characterized in oocytes, Al-activated malate efflux was detected for the Ta::At chimera but not for At::Ta, suggesting that the N-terminal half of TaALMT1 is necessary for function in oocytes. An additional chimera, Ta(48)::At, generated by swapping 17 residues from the N-terminus of AtALMT1 with the equivalent 48 residues from TaALMT1, was sufficient to support transport activity. This 48 residue region includes a helical region with a putative transmembrane domain which is absent in AtALMT1. The deletion of this domain from Ta(48)::At led to the complete loss of transport activity. Furthermore, truncations and a deletion at the C-terminal end of TaALMT1 indicated that a putative helical structure in this region was also required for transport function. This study provides insights into the structure-function relationships of Al-activated ALMT proteins by identifying specific domains on the N- and C-termini of TaALMT1 that are critical for basal transport function and Al responsiveness in oocytes., (© The Author 2014. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email: journals.permissions@oup.com.)
- Published
- 2014
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9. Introgression of a 4D chromosomal fragment into durum wheat confers aluminium tolerance.
- Author
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Han C, Ryan PR, Yan Z, and Delhaize E
- Subjects
- DNA, Plant genetics, Hydroponics, Inbreeding, Malates metabolism, Plant Leaves drug effects, Plant Leaves genetics, Plant Leaves physiology, Plant Proteins metabolism, Plant Roots drug effects, Plant Roots genetics, Plant Roots physiology, Seedlings drug effects, Seedlings genetics, Seedlings physiology, Sodium toxicity, Soil, Triticum drug effects, Triticum genetics, Aluminum toxicity, Chromosomes, Plant genetics, Plant Proteins genetics, Triticum physiology
- Abstract
Background and Aim: Aluminium (Al(3+)) inhibits root growth of sensitive plant species and is a key factor that limits durum wheat (Triticum turgidum) production on acid soils. The aim of this study was to enhance the Al(3+) tolerance of an elite durum cultivar by introgression of a chromosomal fragment from hexaploid wheat (Triticum aestivum) that possesses an Al(3+) tolerance gene., Methods: A 4D(4B) substitution line of durum wheat 'Langdon' was backcrossed to 'Jandaroi', a current semi-dwarf Australian durum. In the second backcross, using 'Jandaroi' as the recurrent parent, a seedling was identified where TaALMT1 on chromosome 4D was recombined with the Rht-B1b locus on chromosome 4B to yield an Al(3+)-tolerant seedling with a semi-dwarf habit. This seedling was used in a third backcross to generate homozygous sister lines with contrasting Al(3+) tolerances. The backcrossed lines were characterized and compared with selected cultivars of hexaploid wheat for their Al(3+) and Na(+) tolerances in hydroponic culture as well as in short-term experiments to assess their growth on acid soil., Key Results: Analysis of sister lines derived from the third backcross showed that the 4D chromosomal fragment substantially enhanced Al(3+) tolerance. The ability to exclude Na(+) from leaves was also enhanced, indicating that the chromosomal fragment possessed the Kna1 salt tolerance locus. Although Al(3+) tolerance of seminal roots was enhanced in acid soil, the development of fine roots was not as robust as found in Al(3+)-tolerant lines of hexaploid wheat. Analysis of plant characteristics in the absence of Al(3+) toxicity showed that the introgressed fragment did not affect total grain yield but reduced the weight of individual grains., Conclusions: The results show that it is possible to increase substantially the Al(3+) tolerance of an elite durum wheat cultivar by introgression of a 4D chromosomal fragment. Further improvements are possible, such as introducing additional genes to enhance the Al(3+) tolerance of fine roots and by eliminating the locus on the chromosomal fragment responsible for smaller grain weights., (© The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)
- Published
- 2014
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10. Enhancing the aluminium tolerance of barley by expressing the citrate transporter genes SbMATE and FRD3.
- Author
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Zhou G, Pereira JF, Delhaize E, Zhou M, Magalhaes JV, and Ryan PR
- Subjects
- Arabidopsis Proteins metabolism, Carrier Proteins metabolism, Hordeum genetics, Membrane Transport Proteins metabolism, Plant Proteins metabolism, Plants, Genetically Modified genetics, Up-Regulation, Aluminum metabolism, Arabidopsis Proteins genetics, Carrier Proteins genetics, Gene Expression, Hordeum metabolism, Membrane Transport Proteins genetics, Plant Proteins genetics, Plants, Genetically Modified metabolism, Sorghum genetics
- Abstract
Malate and citrate efflux from root apices is a mechanism of Al(3+) tolerance in many plant species. Citrate efflux is facilitated by members of the MATE (multidrug and toxic compound exudation) family localized to the plasma membrane of root cells. Barley (Hordeum vulgare) is among the most Al(3+)-sensitive cereal species but the small genotypic variation in tolerance that is present is correlated with citrate efflux via a MATE transporter named HvAACT1. This study used a biotechnological approach to increase the Al(3+) tolerance of barley by transforming it with two MATE genes that encode citrate transporters: SbMATE is the major Al(3+)-tolerance gene from sorghum whereas FRD3 is involved with Fe nutrition in Arabidopsis. Independent transgenic and null T3 lines were generated for both transgenes. Lines expressing SbMATE showed Al(3+)-activated citrate efflux from root apices and greater tolerance to Al(3+) toxicity than nulls in hydroponic and short-term soil trials. Transgenic lines expressing FRD3 exhibited similar phenotypes except citrate release from roots occurred constitutively. The Al(3+) tolerance of these lines was compared with previously generated transgenic barley lines overexpressing the endogenous HvAACT1 gene and the TaALMT1 gene from wheat. Barley lines expressing TaALMT1 showed significantly greater Al(3+) tolerance than all lines expressing MATE genes. This study highlights the relative efficacy of different organic anion transport proteins for increasing the Al(3+) tolerance of an important crop species., (© The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.)
- Published
- 2014
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11. The barley MATE gene, HvAACT1, increases citrate efflux and Al(3+) tolerance when expressed in wheat and barley.
- Author
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Zhou G, Delhaize E, Zhou M, and Ryan PR
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- Carrier Proteins genetics, Carrier Proteins metabolism, Hordeum metabolism, Plant Proteins genetics, Plant Proteins metabolism, Plants, Genetically Modified metabolism, Aluminum metabolism, Carrier Proteins physiology, Citric Acid metabolism, Hordeum genetics, Plant Proteins physiology, Triticum genetics
- Abstract
Background and Aims: Aluminium is toxic in acid soils because the soluble Al(3+) inhibits root growth. A mechanism of Al(3+) tolerance discovered in many plant species involves the release of organic anions from root apices. The Al(3+)-activated release of citrate from the root apices of Al(3+)-tolerant genotypes of barley is controlled by a MATE gene named HvAACT1 that encodes a citrate transport protein located on the plasma membrane. The aim of this study was to investigate whether expressing HvAACT1 with a constitutive promoter in barley and wheat can increase citrate efflux and Al(3+) tolerance of these important cereal species., Methods: HvAACT1 was over-expressed in wheat (Triticum aestivum) and barley (Hordeum vulgare) using the maize ubiquitin promoter. Root apices of transgenic and control lines were analysed for HvAACT1 expression and organic acid efflux. The Al(3+) tolerance of transgenic and control lines was assessed in both hydroponic solution and acid soil., Key Results and Conclusions: Increased HvAACT1 expression in both cereal species was associated with increased citrate efflux from root apices and enhanced Al(3+) tolerance, thus demonstrating that biotechnology can complement traditional breeding practices to increase the Al(3+) tolerance of important crop plants.
- Published
- 2013
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12. Transcriptional regulation of aluminium tolerance genes.
- Author
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Delhaize E, Ma JF, and Ryan PR
- Subjects
- Adaptation, Physiological drug effects, Aluminum toxicity, Hydrogen-Ion Concentration drug effects, Adaptation, Physiological genetics, Aluminum pharmacology, Gene Expression Regulation, Plant drug effects, Genes, Plant genetics, Transcription, Genetic drug effects
- Abstract
Trivalent aluminium (Al(3+)) is the major toxin encountered by plants on acid soils. These cations inhibit root growth by damaging cells at the root apex. The physiology and genetics of Al(3+) tolerance mechanisms involving organic anion efflux from roots have now been investigated in a range of species. Over the past decade, genes encoding these and other newly discovered mechanisms of tolerance have been cloned. In this review, we describe the genes controlling the genotypic variation in Al(3+) tolerance for several important crop species. We focus on recent insights into the transcriptional regulation of these and other genes involved in Al(3+) tolerance and discuss the pathways coordinating their expression in Arabidopsis and rice., (Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.)
- Published
- 2012
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13. Genome-wide association analyses of common wheat (Triticum aestivum L.) germplasm identifies multiple loci for aluminium resistance.
- Author
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Raman H, Stodart B, Ryan PR, Delhaize E, Emebiri L, Raman R, Coombes N, and Milgate A
- Subjects
- Alleles, Drug Resistance genetics, Genetic Variation, Organic Anion Transporters genetics, Polymorphism, Genetic, Quantitative Trait Loci, Triticum drug effects, Aluminum toxicity, Chromosomes, Plant genetics, Genome-Wide Association Study, Triticum genetics
- Abstract
Aluminium (Al3+) toxicity restricts productivity and profitability of wheat (Triticum aestivum L.) crops grown on acid soils worldwide. Continued gains will be obtained by identifying superior alleles and novel Al3+ resistance loci that can be incorporated into breeding programs. We used association mapping to identify genomic regions associated with Al3+ resistance using 1055 accessions of common wheat from different geographic regions of the world and 178 polymorphic diversity arrays technology (DArT) markers. Bayesian analyses based on genetic distance matrices classified these accessions into 12 subgroups. Genome-wide association analyses detected markers that were significantly associated with Al3+ resistance on chromosomes 1A, 1B, 2A, 2B, 2D, 3A, 3B, 4A, 4B, 4D, 5B, 6A, 6B, 7A, and 7B. Some of these genomic regions correspond to previously identified loci for Al3+ resistance, whereas others appear to be novel. Among the markers targeting TaALMT1 (the major Al3+-resistance gene located on chromosome 4D), those that detected alleles in the promoter explained most of the phenotypic variance for Al3+ resistance, which is consistent with this region controlling the level of TaALMT1 expression. These results demonstrate that genome-wide association mapping cannot only confirm known Al3+-resistance loci, such as those on chromosomes 4D and 4B, but they also highlight the utility of this technique in identifying novel resistance loci.
- Published
- 2010
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14. The multiple origins of aluminium resistance in hexaploid wheat include Aegilops tauschii and more recent cis mutations to TaALMT1.
- Author
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Ryan PR, Raman H, Gupta S, Sasaki T, Yamamoto Y, and Delhaize E
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- Alleles, Evolution, Molecular, Gene Expression Regulation, Plant, Genes, Plant, Malates metabolism, Mutation, Organic Anion Transporters genetics, Phylogeny, Plant Proteins genetics, Plants, Genetically Modified genetics, Plants, Genetically Modified metabolism, Promoter Regions, Genetic, Triticum metabolism, Aluminum pharmacology, Organic Anion Transporters metabolism, Plant Proteins metabolism, Tandem Repeat Sequences, Triticum genetics
- Abstract
Acid soils limit plant production worldwide because their high concentrations of soluble aluminium cations (Al(3+) ) inhibit root growth. Major food crops such as wheat (Triticum aestivum L.) have evolved mechanisms to resist Al(3+) toxicity, thus enabling wider distribution. The origins of Al(3+) resistance in wheat are perplexing because all progenitors of this hexaploid species are reportedly sensitive to Al(3+) stress. The large genotypic variation for Al(3+) resistance in wheat is largely controlled by expression of an anion channel, TaALMT1, which releases malate anions from the root apices. A current hypothesis proposes that the malate anions protect this sensitive growth zone by binding to Al(3+) in the apoplasm. We investigated the evolution of this trait in wheat, and demonstrated that it has multiple independent origins that enhance Al(3+) resistance by increasing TaALMT1 expression. One origin is likely to be Aegilops tauschii while other origins occurred more recently from a series of cis mutations that have generated tandemly repeated elements in the TaALMT1 promoter. We generated transgenic plants to directly compare these promoter alleles and demonstrate that the tandemly repeated elements act to enhance gene expression. This study provides an example from higher eukaryotes in which perfect tandem repeats are linked with transcriptional regulation and phenotypic change in the context of evolutionary adaptation to a major abiotic stress., (© 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd.)
- Published
- 2010
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15. An extracellular hydrophilic carboxy-terminal domain regulates the activity of TaALMT1, the aluminum-activated malate transport protein of wheat.
- Author
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Furuichi T, Sasaki T, Tsuchiya Y, Ryan PR, Delhaize E, and Yamamoto Y
- Subjects
- Amino Acid Motifs, Amino Acid Sequence, Biological Transport, Molecular Sequence Data, Mutagenesis, Site-Directed, Mutation, Organic Anion Transporters genetics, Plant Proteins genetics, Triticum metabolism, Aluminum metabolism, Organic Anion Transporters metabolism, Plant Proteins metabolism, Triticum genetics
- Abstract
Al³+ -resistant cultivars of wheat (Triticum aestivum L.) release malate through the Al³+ -activated anion transport protein Triticum aestivum aluminum-activated malate transporter 1 (TaALMT1). Expression of TaALMT1 in Xenopus oocytes and tobacco suspension cells enhances the basal transport activity (inward and outward currents present in the absence of external Al³+, and generates the same Al³+ -activated currents (reflecting the Al³+-dependent transport function) as observed in wheat cells. We investigated the amino acid residues involved in this Al³+-dependent transport activity by generating a series of mutations to the TaALMT1 protein. We targeted the acidic residues on the hydrophilic C-terminal domain of TaALMT1 and changed them to uncharged residues by site-directed mutagenesis. These mutant proteins were expressed in Xenopus oocytes and their transport activity was measured before and after Al³+ addition. Three mutations (E274Q, D275N and E284Q) abolished the Al³+-activated transport activity without affecting the basal transport activity. Truncation of the hydrophilic C-terminal domain abolished both basal and Al³+-activated transport activities. Al³+-dependent transport activity was recovered by fusing the N-terminal region of TaALMT1 with the C-terminal region of AtALMT1, a homolog from Arabidopsis. These findings demonstrate that the extracellular C-terminal domain is required for both basal and Al³+-dependent TaALMT1 activity. Furthermore, we identified three acidic amino acids within this domain that are specifically required for the activation of transport function by external Al³+., (© 2010 The Authors. Journal compilation © 2010 Blackwell Publishing Ltd.)
- Published
- 2010
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16. Engineering greater aluminium resistance in wheat by over-expressing TaALMT1.
- Author
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Pereira JF, Zhou G, Delhaize E, Richardson T, Zhou M, and Ryan PR
- Subjects
- Blotting, Southern, Malates metabolism, Plant Proteins genetics, Plants, Genetically Modified drug effects, Plants, Genetically Modified genetics, Plants, Genetically Modified metabolism, Promoter Regions, Genetic genetics, Reverse Transcriptase Polymerase Chain Reaction, Soil, Triticum genetics, Triticum metabolism, Aluminum toxicity, Genetic Engineering methods, Plant Proteins physiology, Triticum drug effects
- Abstract
Background and Aims: Expected increases in world population will continue to make demands on agricultural productivity and food supply. These challenges will only be met by increasing the land under cultivation and by improving the yields obtained on existing farms. Genetic engineering can target key traits to improve crop yields and to increase production on marginal soils. Soil acidity is a major abiotic stress that limits plant production worldwide. The goal of this study was to enhance the acid soil tolerance of wheat by increasing its resistance to Al(3+) toxicity., Methods: Particle bombardment was used to transform wheat with TaALMT1, the Al(3+) resistance gene from wheat, using the maize ubiquitin promoter to drive expression. TaALMT1 expression, malate efflux and Al(3+) resistance were measured in the T(1) and T(2) lines and compared with the parental line and an Al(3+)-resistant reference genotype, ET8., Key Results: Nine T(2) lines showed increased TaALMT1 expression, malate efflux and Al(3+) resistance when compared with untransformed controls and null segregant lines. Some T(2) lines displayed greater Al(3+) resistance than ET8 in both hydroponic and soil experiments., Conclusions: The Al(3+) resistance of wheat was increased by enhancing TaALMT1 expression with biotechnology. This is the first report of a major food crop being stably transformed for greater Al(3+) resistance. Transgenic strategies provide options for increasing food supply on acid soils.
- Published
- 2010
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17. Transgenic barley (Hordeum vulgare L.) expressing the wheat aluminium resistance gene (TaALMT1) shows enhanced phosphorus nutrition and grain production when grown on an acid soil.
- Author
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Delhaize E, Taylor P, Hocking PJ, Simpson RJ, Ryan PR, and Richardson AE
- Subjects
- Acids metabolism, Gene Expression Regulation, Plant, Genes, Plant, Hordeum drug effects, Hordeum growth & development, Hordeum metabolism, Hydrogen-Ion Concentration, Organic Anion Transporters genetics, Plant Proteins genetics, Plant Roots drug effects, Plant Roots genetics, Plant Roots growth & development, Plant Roots metabolism, Plants, Genetically Modified drug effects, Plants, Genetically Modified genetics, Plants, Genetically Modified growth & development, Plants, Genetically Modified metabolism, Soil, Triticum genetics, Aluminum pharmacology, Hordeum genetics, Organic Anion Transporters metabolism, Phosphorus metabolism, Plant Proteins metabolism
- Abstract
Barley (Hordeum vulgare L.), genetically modified with the Al(3+) resistance gene of wheat (TaALMT1), was compared with a non-transformed sibling line when grown on an acidic and highly phosphate-fixing ferrosol supplied with a range of phosphorus concentrations. In short-term pot trials (26 days), transgenic barley expressing TaALMT1 (GP-ALMT1) was more efficient than a non-transformed sibling line (GP) at taking up phosphorus on acid soil, but the genotypes did not differ when the soil was limed. Differences in phosphorus uptake efficiency on acid soil could be attributed not only to the differential effects of aluminium toxicity on root growth between the genotypes, but also to differences in phosphorus uptake per unit root length. Although GP-ALMT1 out-performed GP on acid soil, it was still not as efficient at taking up phosphorus as plants grown on limed soil. GP-ALMT1 plants grown in acid soil possessed substantially smaller rhizosheaths than those grown in limed soil, suggesting that root hairs were shorter. This is a probable reason for the lower phosphorus uptake efficiency. When grown to maturity in large pots, GP-ALMT1 plants produced more than twice the grain as GP plants grown on acid soil and 80% of the grain produced by limed controls. Expression of TaALMT1 in barley was not associated with a penalty in either total shoot or grain production in the absence of Al(3+), with both genotypes showing equivalent yields in limed soil. These findings demonstrate that an important crop species can be genetically engineered to successfully increase grain production on an acid soil.
- Published
- 2009
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18. A second mechanism for aluminum resistance in wheat relies on the constitutive efflux of citrate from roots.
- Author
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Ryan PR, Raman H, Gupta S, Horst WJ, and Delhaize E
- Subjects
- Biological Transport, Active, Chromosome Mapping, Expressed Sequence Tags, Gene Expression Regulation, Plant, Genes, Plant, Genotype, Molecular Sequence Data, Organic Anion Transporters genetics, Plant Proteins genetics, Plant Proteins metabolism, Plant Roots genetics, RNA, Plant metabolism, Triticum metabolism, Aluminum metabolism, Citric Acid metabolism, Organic Anion Transporters metabolism, Plant Roots metabolism, Triticum genetics
- Abstract
The first confirmed mechanism for aluminum (Al) resistance in plants is encoded by the wheat (Triticum aestivum) gene, TaALMT1, on chromosome 4DL. TaALMT1 controls the Al-activated efflux of malate from roots, and this mechanism is widespread among Al-resistant genotypes of diverse genetic origins. This study describes a second mechanism for Al resistance in wheat that relies on citrate efflux. Citrate efflux occurred constitutively from the roots of Brazilian cultivars Carazinho, Maringa, Toropi, and Trintecinco. Examination of two populations segregating for this trait showed that citrate efflux was controlled by a single locus. Whole-genome linkage mapping using an F(2) population derived from a cross between Carazinho (citrate efflux) and the cultivar EGA-Burke (no citrate efflux) identified a major locus on chromosome 4BL, Xce(c), which accounts for more than 50% of the phenotypic variation in citrate efflux. Mendelizing the quantitative variation in citrate efflux into qualitative data, the Xce(c) locus was mapped within 6.3 cM of the microsatellite marker Xgwm495 locus. This linkage was validated in a second population of F(2:3) families derived from a cross between Carazinho and the cultivar Egret (no citrate efflux). We show that expression of an expressed sequence tag, belonging to the multidrug and toxin efflux (MATE) gene family, correlates with the citrate efflux phenotype. This study provides genetic and physiological evidence that citrate efflux is a second mechanism for Al resistance in wheat.
- Published
- 2009
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19. Characterization of the TaALMT1 protein as an Al3+-activated anion channel in transformed tobacco (Nicotiana tabacum L.) cells.
- Author
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Zhang WH, Ryan PR, Sasaki T, Yamamoto Y, Sullivan W, and Tyerman SD
- Subjects
- Cells, Cultured, Electrophysiology, Ion Transport, Malates metabolism, Membrane Potentials, Organic Anion Transporters genetics, Plant Proteins genetics, Plants, Genetically Modified metabolism, Protoplasts metabolism, Nicotiana genetics, Transformation, Genetic, Triticum metabolism, Voltage-Dependent Anion Channels metabolism, Aluminum metabolism, Organic Anion Transporters metabolism, Plant Proteins metabolism, Nicotiana metabolism, Triticum genetics
- Abstract
TaALMT1 encodes a putative transport protein associated with Al(3+)-activated efflux of malate from wheat root apices. We expressed TaALMT1 in Nicotiana tabacum L. suspension cells and conducted a detailed functional analysis. Protoplasts were isolated for patch-clamping from cells expressing TaALMT1 and from control cells (empty vector transformed). With malate(2-) as the permeant anion in the protoplast, an inward current (anion efflux) that reversed at positive potentials was observed in protoplasts expressing TaALMT1 in the absence of Al(3+). This current was sensitive to the anion channel antagonist niflumate, but insensitive to Gd(3+). External AlCl(3) (50 microM), but not La(3+) and Gd(3+), increased the inward current in TaALMT1-transformed protoplasts. The inward current was highly selective to malate over nitrate and chloride (P(mal) >> P(NO3) >or= P(Cl), P(mal)/P(Cl) >or=18, +/-Al(3+)), under conditions with higher anion concentration internally than externally. The anion currents displayed a voltage and time dependent deactivation at negative voltages. Voltage ramps revealed that inward rectification was caused by the imposed anion gradients. Single channels with conductances between 10 and 17 pS were associated with the deactivation of the current at negative voltages, agreeing with estimates from voltage ramps. This study of the electrophysiological function of the TaALMT1 protein in a plant heterologous expression system provides the first direct evidence that TaALMT1 functions as an Al(3+)-activated malate(2-) channel. We show that the Al(3+)-activated currents measured in TaALMT1-transformed tobacco cells are identical to the Al(3+)-activated currents observed in the root cells of wheat, indicating that TaALMT1 alone is likely to be responsible for those endogenous currents.
- Published
- 2008
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20. Analysis of TaALMT1 traces the transmission of aluminum resistance in cultivated common wheat (Triticum aestivum L.).
- Author
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Raman H, Ryan PR, Raman R, Stodart BJ, Zhang K, Martin P, Wood R, Sasaki T, Yamamoto Y, Mackay M, Hebb DM, and Delhaize E
- Subjects
- Alleles, Aluminum metabolism, Breeding, Chromosome Segregation, Genetic Markers, Geography, Haploidy, Haplotypes, Malates metabolism, Plant Roots growth & development, Polymerase Chain Reaction, Promoter Regions, Genetic genetics, Agriculture, Aluminum pharmacology, Drug Resistance genetics, Organic Anion Transporters genetics, Triticum drug effects, Triticum genetics
- Abstract
Allele diversities of four markers specific to intron three, exon four and promoter regions of the aluminum (Al) resistance gene of wheat (Triticum aestivum L.) TaALMT1 were compared in 179 common wheat cultivars used in international wheat breeding programs. In wheat cultivars released during the last 93 years, six different promoter types were identified on the basis of allele size. A previous study showed that Al resistance was not associated with a particular coding allele for TaALMT1 but was correlated with blocks of repeated sequence upstream of the coding sequence. We verified the linkage between these promoter alleles and Al resistance in three doubled haploid and one intercross populations segregating for Al resistance. Molecular and pedigree analysis suggest that Al resistance in modern wheat germplasm is derived from several independent sources. Analysis of a population of 278 landraces and subspecies of wheat showed that most of the promoter alleles associated with Al resistance pre-existed in Europe, the Middle East and Asia prior to dispersal of cultivated germplasm around the world. Furthermore, several new promoter alleles were identified among the landraces surveyed. The TaALMT1 promoter alleles found within the spelt wheats were consistent with the hypothesis that these spelts arose on several independent occasions from hybridisations between non-free-threshing tetraploid wheats and Al-resistant hexaploid bread wheats. The strong correlation between Al resistance and Al-stimulated malate efflux from the root apices of 49 diverse wheat genotypes examined was consistent with the previous finding that Al resistance in wheat is conditioned primarily by malate efflux. These results demonstrate that the markers based on intron, exon and promoter regions of TaALMT1 can trace the inheritance of the Al resistance locus within wheat pedigrees and track Al resistance in breeding programmes.
- Published
- 2008
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21. A higher plant delta8 sphingolipid desaturase with a preference for (Z)-isomer formation confers aluminum tolerance to yeast and plants.
- Author
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Ryan PR, Liu Q, Sperling P, Dong B, Franke S, and Delhaize E
- Subjects
- Arabidopsis genetics, Arabidopsis metabolism, DNA, Complementary, Fabaceae genetics, Fabaceae metabolism, Genes, Plant, Plants, Genetically Modified metabolism, Saccharomyces cerevisiae genetics, Sphingosine metabolism, Aluminum metabolism, Fabaceae enzymology, Oxidoreductases metabolism, Sphingosine analogs & derivatives
- Abstract
Three plant cDNA libraries were expressed in yeast (Saccharomyces cerevisiae) and screened on agar plates containing toxic concentrations of aluminum. Nine cDNAs were isolated that enhanced the aluminum tolerance of yeast. These cDNAs were constitutively expressed in Arabidopsis (Arabidopsis thaliana) and one cDNA from the roots of Stylosanthes hamata, designated S851, conferred greater aluminum tolerance to the transgenic seedlings. The protein predicted to be encoded by S851 showed an equally high similarity to Delta6 fatty acyl lipid desaturases and Delta8 sphingolipid desaturases. We expressed other known Delta6 desaturase and Delta8 desaturase genes in yeast and showed that a Delta6 fatty acyl desaturase from Echium plantagineum did not confer aluminum tolerance, whereas a Delta8 sphingobase desaturase from Arabidopsis did confer aluminum tolerance. Analysis of the fatty acids and sphingobases of the transgenic yeast and plant cells demonstrated that S851 encodes a Delta8 sphingobase desaturase, which leads to the accumulation of 8(Z/E)-C(18)-phytosphingenine and 8(Z/E)-C(20)-phytopshingenine in yeast and to the accumulation of 8(Z/E)-C(18)-phytosphingenine in the leaves and roots of Arabidopsis plants. The newly formed 8(Z/E)-C(18)-phytosphingenine in transgenic yeast accounted for 3 mol% of the total sphingobases with a 8(Z):8(E)-isomer ratio of approximately 4:1. The accumulation of 8(Z)-C(18)-phytosphingenine in transgenic Arabidopsis shifted the ratio of the 8(Z):8(E) isomers from 1:4 in wild-type plants to 1:1 in transgenic plants. These results indicate that S851 encodes the first Delta8 sphingolipid desaturase to be identified in higher plants with a preference for the 8(Z)-isomer. They further demonstrate that changes in the sphingolipid composition of cell membranes can protect plants from aluminum stress.
- Published
- 2007
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22. High-resolution mapping of the Alp locus and identification of a candidate gene HvMATE controlling aluminium tolerance in barley (Hordeum vulgare L.).
- Author
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Wang J, Raman H, Zhou M, Ryan PR, Delhaize E, Hebb DM, Coombes N, and Mendham N
- Subjects
- Chromosome Mapping, Citric Acid metabolism, Genetic Markers, Genome, Plant, Hordeum metabolism, Oryza genetics, Plant Proteins physiology, Polymorphism, Single Nucleotide, Secale genetics, Synteny, Triticum genetics, Aluminum metabolism, Hordeum genetics, Plant Proteins genetics
- Abstract
Aluminium (Al) tolerance in barley is conditioned by the Alp locus on the long arm of chromosome 4H, which is associated with Al-activated release of citrate from roots. We developed a high-resolution map of the Alp locus using 132 doubled haploid (DH) lines from a cross between Dayton (Al-tolerant) and Zhepi 2 (Al-sensitive) and 2,070 F(2 )individuals from a cross between Dayton and Gairdner (Al-sensitive). The Al-activated efflux of citrate from the root apices of Al-tolerant Dayton was 10-fold greater than from the Al-sensitive parents Zhepi 2 and Gairdner. A suite of markers (ABG715, Bmag353, GBM1071, GWM165, HvMATE and HvGABP) exhibited complete linkage with the Alp locus in the DH population accounting 72% of the variation for Al tolerance evaluated as relative root elongation. These markers were used to map this genomic region in the Dayton/Gairdner population in more detail. Flanking markers HvGABP and ABG715 delineated the Alp locus to a 0.2 cM interval. Since the HvMATE marker was not polymorphic in the Dayton/Gairdner population we instead investigated the expression of the HvMATE gene. Relative expression of the HvMATE gene was 30-fold greater in Dayton than Gardiner. Furthermore, HvMATE expression in the F(2:3) families tested, including all the informative recombinant lines identified between HvGABP and ABG715 was significantly correlated with Al tolerance and Al-activated citrate efflux. These results identify HvMATE, a gene encoding a multidrug and toxic compound extrusion protein, as a candidate controlling Al tolerance in barley.
- Published
- 2007
- Full Text
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23. The roles of organic anion permeases in aluminium resistance and mineral nutrition.
- Author
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Delhaize E, Gruber BD, and Ryan PR
- Subjects
- ATP-Binding Cassette Transporters chemistry, ATP-Binding Cassette Transporters genetics, ATP-Binding Cassette Transporters metabolism, Biological Evolution, Drug Resistance genetics, Genes, Plant, Ion Transport genetics, Membrane Transport Proteins chemistry, Membrane Transport Proteins genetics, Minerals metabolism, Models, Biological, Models, Molecular, Organic Anion Transporters chemistry, Organic Anion Transporters genetics, Phosphorus metabolism, Phylogeny, Plant Proteins chemistry, Plant Proteins genetics, Plants genetics, Protein Structure, Secondary, Aluminum toxicity, Membrane Transport Proteins metabolism, Organic Anion Transporters metabolism, Plant Proteins metabolism, Plants drug effects, Plants metabolism
- Abstract
Soluble aluminium (Al(3+)) is the major constraint to plant growth on acid soils. Plants have evolved mechanisms to tolerate Al(3+) and one type of mechanism relies on the efflux of organic anions that protect roots by chelating the Al(3+). Al(3+) resistance genes of several species have now been isolated and found to encode membrane proteins that facilitate organic anion efflux from roots. These proteins belong to the Al(3+)-activated malate transporter (ALMT) and multi-drug and toxin extrusion (MATE) families. We review the roles of these proteins in Al(3+) resistance as well as their roles in other aspects of mineral nutrition.
- Published
- 2007
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24. The BnALMT1 and BnALMT2 genes from rape encode aluminum-activated malate transporters that enhance the aluminum resistance of plant cells.
- Author
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Ligaba A, Katsuhara M, Ryan PR, Shibasaka M, and Matsumoto H
- Subjects
- Amino Acid Sequence, Biological Transport, Active drug effects, Brassica napus drug effects, Brassica napus genetics, Cells, Cultured, Gene Expression Regulation, Plant, Molecular Sequence Data, Plant Proteins genetics, Nicotiana cytology, Aluminum pharmacology, Brassica napus cytology, Brassica napus metabolism, Malates metabolism, Organic Anion Transporters genetics, Organic Anion Transporters metabolism, Plant Proteins metabolism
- Abstract
The release of organic anions from roots can protect plants from aluminum (Al) toxicity and help them overcome phosphorus (P) deficiency. Our previous findings showed that Al treatment induced malate and citrate efflux from rape (Brassica napus) roots, and that P deficiency did not induce the efflux. Since this response is similar to the malate efflux from wheat (Triticum aestivum) that is controlled by the TaALMT1 gene, we investigated whether homologs of TaALMT1 are present in rape and whether they are involved in the release of organic anions. We isolated two TaALMT1 homologs from rape designated BnALMT1 and BnALMT2 (B. napus Al-activated malate transporter). The expression of these genes was induced in roots, but not shoots, by Al treatment but P deficiency had no effect. Several other cations (lanthanum, ytterbium, and erbium) also increased BnALMT1 and BnALMT2 expression in the roots. The function of the BnALMT1 and BnALMT2 proteins was investigated by heterologous expression in cultured tobacco (Nicotiana tabacum) cells and in Xenopus laevis oocytes. Both transfection systems showed an enhanced capacity for malate efflux but not citrate efflux, when exposed to Al. Smaller malate fluxes were also activated by ytterbium and erbium treatment. Transgenic tobacco cells grew significantly better than control cells following an 18 h treatment with Al, indicating that the expression of BnALMT1 and BnALMT2 increased the resistance of these plant cells to Al stress. This report demonstrates that homologs of the TaALMT1 gene from wheat perform similar functions in other species.
- Published
- 2006
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25. Sequence upstream of the wheat (Triticum aestivum L.) ALMT1 gene and its relationship to aluminum resistance.
- Author
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Sasaki T, Ryan PR, Delhaize E, Hebb DM, Ogihara Y, Kawaura K, Noda K, Kojima T, Toyoda A, Matsumoto H, and Yamamoto Y
- Subjects
- Base Sequence, Gene Expression Regulation, Plant, Malates metabolism, Molecular Sequence Data, Organic Anion Transporters metabolism, Triticum metabolism, Aluminum metabolism, Organic Anion Transporters genetics, Triticum genetics
- Abstract
Aluminum (Al) resistance in wheat relies on the Al-activated malate efflux from root apices, which appears to be controlled by an Al-activated anion transporter encoded by the ALMT1 gene on chromosome 4DL. Genomic regions upstream and downstream of ALMT1 in 69 wheat lines were characterized to identify patterns that might influence ALMT1 expression. The first 1,000 bp downstream of ALMT1 was conserved among the lines examined apart from the presence of a transposon-like sequence which did not correlate with Al resistance. In contrast, the first 1,000 bp upstream of the ALMT1 coding region was more variable and six different patterns could be discerned (types I-VI). Type I had the simplest structure, while the others had blocks of sequence that were duplicated or triplicated in different arrangements. A pattern emerged among the lines of non-Japanese origin such that the number of repeats in this upstream region was positively correlated with the levels of ALMT1 expression and Al resistance. In contrast, many of the Japanese lines exhibited a large variation in ALMT1 expression and Al resistance despite possessing the same type of upstream region. Although ALMT1 expression was also poorly correlated with Al-activated malate efflux in the Japanese lines, a strong correlation between malate efflux and Al resistance suggested that malate efflux was still the primary mechanism for Al resistance, and that additional genes are involved in the post-transcriptional regulation of ALMT1 function.
- Published
- 2006
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26. AtALMT1, which encodes a malate transporter, is identified as one of several genes critical for aluminum tolerance in Arabidopsis.
- Author
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Hoekenga OA, Maron LG, Piñeros MA, Cançado GM, Shaff J, Kobayashi Y, Ryan PR, Dong B, Delhaize E, Sasaki T, Matsumoto H, Yamamoto Y, Koyama H, and Kochian LV
- Subjects
- Amino Acids genetics, Amino Acids metabolism, Arabidopsis genetics, Arabidopsis growth & development, Arabidopsis Proteins genetics, DNA, Plant genetics, Electrophysiology, Molecular Sequence Data, Mutation genetics, Organic Anion Transporters genetics, Plant Roots drug effects, Plant Roots metabolism, Polymorphism, Genetic genetics, Aluminum pharmacology, Arabidopsis drug effects, Arabidopsis metabolism, Arabidopsis Proteins metabolism, Genes, Plant genetics, Organic Anion Transporters metabolism
- Abstract
Aluminum (Al) tolerance in Arabidopsis is a genetically complex trait, yet it is mediated by a single physiological mechanism based on Al-activated root malate efflux. We investigated a possible molecular determinant for Al tolerance involving a homolog of the wheat Al-activated malate transporter, ALMT1. This gene, named AtALMT1 (At1g08430), was the best candidate from the 14-member AtALMT family to be involved with Al tolerance based on expression patterns and genomic location. Physiological analysis of a transferred DNA knockout mutant for AtALMT1 as well as electrophysiological examination of the protein expressed in Xenopus oocytes showed that AtALMT1 is critical for Arabidopsis Al tolerance and encodes the Al-activated root malate efflux transporter associated with tolerance. However, gene expression and sequence analysis of AtALMT1 alleles from tolerant Columbia (Col), sensitive Landsberg erecta (Ler), and other ecotypes that varied in Al tolerance suggested that variation observed at AtALMT1 is not correlated with the differences observed in Al tolerance among these ecotypes. Genetic complementation experiments indicated that the Ler allele of AtALMT1 is equally effective as the Col allele in conferring Al tolerance and Al-activated malate release. Finally, fine-scale mapping of a quantitative trait locus (QTL) for Al tolerance on chromosome 1 indicated that AtALMT1 is located proximal to this QTL. These results indicate that AtALMT1 is an essential factor for Al tolerance in Arabidopsis but does not represent the major Al tolerance QTL also found on chromosome 1.
- Published
- 2006
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27. Molecular characterization and mapping of ALMT1, the aluminium-tolerance gene of bread wheat (Triticum aestivum L.).
- Author
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Raman H, Zhang K, Cakir M, Appels R, Garvin DF, Maron LG, Kochian LV, Moroni JS, Raman R, Imtiaz M, Drake-Brockman F, Waters I, Martin P, Sasaki T, Yamamoto Y, Matsumoto H, Hebb DM, Delhaize E, and Ryan PR
- Subjects
- Alleles, Base Sequence, Gene Expression, Gene Frequency, Genetic Linkage, Haploidy, Malates metabolism, Molecular Sequence Data, Polymorphism, Genetic, Quantitative Trait Loci, Sequence Deletion, Triticum genetics, Triticum metabolism, Aluminum toxicity, Chromosomes, Plant genetics, Drug Resistance genetics, Gene Expression Regulation, Plant, Genes, Plant genetics, Triticum drug effects
- Abstract
The major aluminum (Al) tolerance gene in wheat ALMT1 confers. An Al-activated efflux of malate from root apices. We determined the genomic structure of the ALMT1 gene and found it consists of 6 exons interrupted by 5 introns. Sequencing a range of wheat genotypes identified 3 alleles for ALMT1, 1 of which was identical to the ALMT1 gene from an Aegilops tauschii accession. The ALMT1 gene was mapped to chromosome 4DL using 'Chinese Spring' deletion lines, and loss of ALMT1 coincided with the loss of both Al tolerance and Al-activated malate efflux. Aluminium tolerance in each of 5 different doubled-haploid populations was found to be conditioned by a single major gene. When ALMT1 was polymorphic between the parental lines, QTL and linkage analyses indicated that ALMT1 mapped to chromosome 4DL and cosegregated with Al tolerance. In 2 populations examined, Al tolerance also segregated with a greater capacity for Al-activated malate efflux. Aluminium tolerance was not associated with a particular coding allele for ALMT1, but was significantly correlated with the relative level of ALMT1 expression. These findings suggest that the Al tolerance in a diverse range of wheat genotypes is primarily conditioned by ALMT1.
- Published
- 2005
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28. Engineering high-level aluminum tolerance in barley with the ALMT1 gene.
- Author
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Delhaize E, Ryan PR, Hebb DM, Yamamoto Y, Sasaki T, and Matsumoto H
- Subjects
- Base Sequence, Biological Transport, Active drug effects, DNA, Plant genetics, Genetic Engineering, Hordeum metabolism, Malates metabolism, Plant Proteins genetics, Plant Proteins metabolism, Plants, Genetically Modified, Recombinant Proteins genetics, Recombinant Proteins metabolism, Aluminum toxicity, Genes, Plant, Hordeum drug effects, Hordeum genetics
- Abstract
Acidity is a serious limitation to plant production on many of the world's agricultural soils. Toxic aluminium (Al) cations solubilized by the acidity rapidly inhibit root growth and limit subsequent uptake of water and nutrients. Recent work has shown that the ALMT1 gene of wheat (Triticum aestivum) encodes a malate transporter that is associated with malate efflux and Al tolerance. We generated transgenic barley (Hordeum vulgare) plants expressing ALMT1 and assessed their ability to exude malate and withstand Al stress. ALMT1 expression in barley conferred an Al-activated efflux of malate with properties similar to those of Al-tolerant wheat. The transgenic barley showed a high level of Al tolerance when grown in both hydroponic culture and on acid soils. These findings provide additional evidence that ALMT1 is a major Al-tolerance gene and demonstrate its ability to confer effective tolerance to acid soils through a transgenic approach in an important crop species.
- Published
- 2004
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29. A wheat gene encoding an aluminum-activated malate transporter.
- Author
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Sasaki T, Yamamoto Y, Ezaki B, Katsuhara M, Ahn SJ, Ryan PR, Delhaize E, and Matsumoto H
- Subjects
- Adaptation, Physiological, Animals, Cells, Cultured, Cloning, Molecular, DNA, Complementary chemistry, DNA, Complementary genetics, Female, Gene Expression Regulation, Plant drug effects, Membrane Potentials drug effects, Molecular Sequence Data, Oocytes physiology, Organic Anion Transporters metabolism, Plant Proteins metabolism, Sequence Analysis, DNA, Nicotiana cytology, Triticum drug effects, Triticum metabolism, Xenopus laevis, Aluminum pharmacology, Malates metabolism, Organic Anion Transporters genetics, Plant Proteins genetics, Triticum genetics
- Abstract
The major constraint to plant growth in acid soils is the presence of toxic aluminum (Al) cations, which inhibit root elongation. The enhanced Al tolerance exhibited by some cultivars of wheat is associated with the Al-dependent efflux of malate from root apices. Malate forms a stable complex with Al that is harmless to plants and, therefore, this efflux of malate forms the basis of a hypothesis to explain Al tolerance in wheat. Here, we report on the cloning of a wheat gene, ALMT1 (aluminum-activated malate transporter), that co-segregates with Al tolerance in F2 and F3 populations derived from crosses between near-isogenic wheat lines that differ in Al tolerance. The ALMT1 gene encodes a membrane protein, which is constitutively expressed in the root apices of the Al-tolerant line at greater levels than in the near-isogenic but Al-sensitive line. Heterologous expression of ALMT1 in Xenopus oocytes, rice and cultured tobacco cells conferred an Al-activated malate efflux. Additionally, ALMT1 increased the tolerance of tobacco cells to Al treatment. These findings demonstrate that ALMT1 encodes an Al-activated malate transporter that is capable of conferring Al tolerance to plant cells.
- Published
- 2004
- Full Text
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30. Assessing the effectiveness of the TaMATE1B and TaALMT1 genes to enhance the Al3+ tolerance of durum wheat (Triticum turgidum) grown under controlled conditions and in the field
- Author
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Kawasaki, Akitomo, Wasson, Anton P., Kielnhofer, Evangeline, Ryan, Peter R., and Delhaize, Emmanuel
- Published
- 2024
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31. Does the major aluminium-resistance gene in wheat, TaALMT1, also confer tolerance to alkaline soils?
- Author
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Silva, Carolina M. S., Zhang, Chunyan, Habermann, Gustavo, Delhaize, Emmanuel, and Ryan, Peter R.
- Published
- 2018
- Full Text
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32. Direct Evaluation of the Ca²⁺-Displacement Hypothesis for Al Toxicity
- Author
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Ryan, Peter R., Reid, Robert J., and Smith, F. Andrew
- Published
- 1997
33. Effects of altered citrate synthase and isocitrate dehydrogenase expression on internal citrate concentrations and citrate efflux from tobacco (Nicotiana tabacum L.) roots
- Author
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Delhaize, Emmanuel, Ryan, Peter R, Hocking, Peter J, and Richardson, Alan E
- Published
- 2003
34. Strategies to isolate transporters that facilitate organic anion efflux from plant roots
- Author
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Ryan, Peter R., Dong, Bei, Watt, Michelle, Kataoka, Tatsuhiko, and Delhaize, Emmanuel
- Published
- 2003
35. Aluminum Toxicity and Tolerance in Plants
- Author
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Delhaize, Emmanuel and Ryan, Peter R.
- Published
- 1995
36. Interaction between Aluminum Toxicity and Calcium Uptake at the Root Apex in Near-Isogenic Lines of Wheat (Triticum aestivum L.) Differing in Aluminum Tolerance
- Author
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Ryan, Peter R. and Kochian, Leon V.
- Published
- 1993
37. Aluminum Tolerance in Wheat (Triticum aestivum L.): II. Aluminum-Stimulated Excretion of Malic Acid from Root Apices
- Author
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Delhaize, Emmanuel and Ryan, Peter R.
- Published
- 1993
38. Aluminum Toxicity in Roots: Correlation among Ionic Currents, Ion Fluxes, and Root Elongation in Aluminum-Sensitive and Aluminum-Tolerant Wheat Cultivars
- Author
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Ryan, Peter R. and Kochian, Leon V.
- Published
- 1992
39. Interactive Effects of Al₃, H⁺, and Other Cations on Root Elongation Considered in Terms of Cell-Surface Electrical Potential
- Author
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Kinraide, Thomas B., Ryan, Peter R., and Kochian, Leon V.
- Published
- 1992
40. Characterisation of Al-stimulated efflux of malate from the apices of Al-tolerant wheat roots
- Author
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Ryan, Peter R., Delhaize, Emmanuel, and Randall, Peter J.
- Published
- 1995
41. Al 3+ -Ca 2+ interactions in aluminum rhizotoxicity: I. Inhibition of root growth is not caused by reduction of calcium uptake
- Author
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Ryan, Peter R., Kinraide, Thomas B., and Kochian, Leon V.
- Published
- 1994
42. Al 3+ -Ca 2+ interactions in aluminum rhizotoxicity: II. Evaluating the Ca 2+ -displacement hypothesis
- Author
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Kinraide, Thomas B., Ryan, Peter R., and Kochian, Leon V.
- Published
- 1994
43. Aluminium Toxicity in Roots: An Investigation of Spatial Sensitivity and the Role of the Root Cap
- Author
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RYAN, PETER R., DITOMASO, JOSEPH M., and KOCHIAN, LEON V.
- Published
- 1993
44. Does the major aluminium-resistance gene in wheat, <italic>TaALMT1</italic>, also confer tolerance to alkaline soils?
- Author
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Silva, Carolina M. S., Zhang, Chunyan, Habermann, Gustavo, Delhaize, Emmanuel, and Ryan, Peter R.
- Subjects
ACID soils ,SOIL acidity ,SODIC soils ,MINERALOGY ,HYDROPONICS - Abstract
Aim: A major limitation to plant growth in acid soils is the prevalence of toxic Al
3+ . Most genotypic variation for acid soil-tolerance in wheat is linked with the Al3+ -activated efflux of malate anions from roots which is controlled byTaALMT1 on chromosome 4DL. Recent studies have also linkedTaALMT1 with tolerance to high pH solutions and alkaline soils. This study tested the hypothesis that an Al3+ -resistant allele ofTaALMT1 also confers tolerance to alkaline conditions.Methods: The near-isogenic wheat lines, ET8 (Al3+ -resistant) and ES8 (Al3+ -sensitive), have different alleles of theTaALMT1 gene and contrasting resistance to Al3+ toxicity. Growth of these lines was compared in acid and alkaline soils with contrasting mineralogy and in a range of high pH hydroponic solutions of varying composition.Results: No consistent differences in root or shoot growth were detected between the lines in the alkaline soils or in the high pH hydroponic treatments. Malate efflux was detected from ET8 in acidic solution with Al3+ but no substantial malate efflux was detected at pH 9.0 treatment with added Na2 SO4 .Conclusion: The results are inconsistent with the hypothesis that theTaALMT1 gene confers an advantage to wheat on alkaline soils. [ABSTRACT FROM AUTHOR]- Published
- 2018
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45. A Second Mechanism for Aluminum Resistance in Wheat Relies on the Constitutive Efflux of Citrate from Roots1[W][OA]
- Author
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Ryan, Peter R., Raman, Harsh, Gupta, Sanjay, Horst, Walter J., and Delhaize, Emmanuel
- Subjects
Expressed Sequence Tags ,Genotype ,Molecular Sequence Data ,food and beverages ,Biological Transport, Active ,Chromosome Mapping ,Organic Anion Transporters ,Focus Issue on the Grasses ,Genes, Plant ,Plant Roots ,Citric Acid ,Gene Expression Regulation, Plant ,RNA, Plant ,Triticum ,Aluminum ,Plant Proteins - Abstract
The first confirmed mechanism for aluminum (Al) resistance in plants is encoded by the wheat (Triticum aestivum) gene, TaALMT1, on chromosome 4DL. TaALMT1 controls the Al-activated efflux of malate from roots, and this mechanism is widespread among Al-resistant genotypes of diverse genetic origins. This study describes a second mechanism for Al resistance in wheat that relies on citrate efflux. Citrate efflux occurred constitutively from the roots of Brazilian cultivars Carazinho, Maringa, Toropi, and Trintecinco. Examination of two populations segregating for this trait showed that citrate efflux was controlled by a single locus. Whole-genome linkage mapping using an F(2) population derived from a cross between Carazinho (citrate efflux) and the cultivar EGA-Burke (no citrate efflux) identified a major locus on chromosome 4BL, Xce(c), which accounts for more than 50% of the phenotypic variation in citrate efflux. Mendelizing the quantitative variation in citrate efflux into qualitative data, the Xce(c) locus was mapped within 6.3 cM of the microsatellite marker Xgwm495 locus. This linkage was validated in a second population of F(2:3) families derived from a cross between Carazinho and the cultivar Egret (no citrate efflux). We show that expression of an expressed sequence tag, belonging to the multidrug and toxin efflux (MATE) gene family, correlates with the citrate efflux phenotype. This study provides genetic and physiological evidence that citrate efflux is a second mechanism for Al resistance in wheat.
- Published
- 2009
46. The BnALMT1 and BnALMT2 Genes from Rape Encode Aluminum-Activated Malate Transporters That Enhance the Aluminum Resistance of Plant Cells1
- Author
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Ligaba, Ayalew, Katsuhara, Maki, Ryan, Peter R., Shibasaka, Mineo, and Matsumoto, Hideaki
- Subjects
Gene Expression Regulation, Plant ,Brassica napus ,Molecular Sequence Data ,Tobacco ,Malates ,food and beverages ,Biological Transport, Active ,Organic Anion Transporters ,Amino Acid Sequence ,Cells, Cultured ,Research Article ,Aluminum ,Plant Proteins - Abstract
The release of organic anions from roots can protect plants from aluminum (Al) toxicity and help them overcome phosphorus (P) deficiency. Our previous findings showed that Al treatment induced malate and citrate efflux from rape (Brassica napus) roots, and that P deficiency did not induce the efflux. Since this response is similar to the malate efflux from wheat (Triticum aestivum) that is controlled by the TaALMT1 gene, we investigated whether homologs of TaALMT1 are present in rape and whether they are involved in the release of organic anions. We isolated two TaALMT1 homologs from rape designated BnALMT1 and BnALMT2 (B. napus Al-activated malate transporter). The expression of these genes was induced in roots, but not shoots, by Al treatment but P deficiency had no effect. Several other cations (lanthanum, ytterbium, and erbium) also increased BnALMT1 and BnALMT2 expression in the roots. The function of the BnALMT1 and BnALMT2 proteins was investigated by heterologous expression in cultured tobacco (Nicotiana tabacum) cells and in Xenopus laevis oocytes. Both transfection systems showed an enhanced capacity for malate efflux but not citrate efflux, when exposed to Al. Smaller malate fluxes were also activated by ytterbium and erbium treatment. Transgenic tobacco cells grew significantly better than control cells following an 18 h treatment with Al, indicating that the expression of BnALMT1 and BnALMT2 increased the resistance of these plant cells to Al stress. This report demonstrates that homologs of the TaALMT1 gene from wheat perform similar functions in other species.
- Published
- 2006
47. Aluminum Complexation with Malate within the Root Apoplast Differs between Aluminum Resistant and Sensitive Wheat Lines.
- Author
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Kopittke, Peter M., McKenna, Brigid A., Karunakaran, Chithra, Dynes, James J., Arthur, Zachary, Gianoncelli, Alessandra, Kourousias, George, Menzies, Neal W., Ryan, Peter R., Peng Wang, Green, Kathryn, and Blamey, F. P. C.
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WHEAT genetics ,ALUMINUM ,RHIZOSPHERE - Abstract
In wheat (Triticum aestivum), it is commonly assumed that Al is detoxified by the release of organic anions into the rhizosphere, but it is also possible that detoxification occurs within the apoplast and symplast of the root itself. Using Al-resistant (ET8) and Al-sensitive (ES8) near-isogenic lines of wheat, we utilized traditional and synchrotronbased approaches to provide in situ analyses of the distribution and speciation of Al within root tissues. Some Al appeared to be complexed external to the root, in agreement with the common assumption. However, root apical tissues of ET8 accumulated four to six times more Al than ES8 when exposed to Al concentrations that reduce root elongation rate by 50% (3.5 mM Al for ES8 and 50 mM for ET8). Furthermore, in situ analyses of ET8 root tissues indicated the likely presence of Al-malate and other forms of Al, predominantly within the apoplast. To our knowledge, this is the first time that X-ray absorption near edge structure analyses have been used to examine the speciation of Al within plant tissues. The information obtained in the present study is important in developing an understanding of the underlying physiological mode of action for improved root growth in systems with elevated soluble Al. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
48. Malate-Permeable Channels and Cation Channels Activated by Aluminum in the Apical Cells of Wheat Roots1
- Author
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Zhang, Wen-Hao, Ryan, Peter R., and Tyerman, Stephen D.
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integumentary system ,Cyclic AMP ,Malates ,Niflumic Acid ,Biological Transport ,ortho-Aminobenzoates ,Plant Roots ,Ion Channels ,Permeability ,Triticum ,Research Article ,Aluminum - Abstract
Aluminum (Al(3+))-dependent efflux of malate from root apices is a mechanism for Al(3+) tolerance in wheat (Triticum aestivum). The malate anions protect the sensitive root tips by chelating the toxic Al(3+) cations in the rhizosphere to form non-toxic complexes. Activation of malate-permeable channels in the plasma membrane could be critical in regulating this malate efflux. We examined this by investigating Al(3+)-activated channels in protoplasts from root apices of near-isogenic wheat differing in Al(3+) tolerance at a single locus. Using whole-cell patch clamp we found that Al(3+) stimulated an electrical current carried by anion efflux across the plasma membrane in the Al(3+)-tolerant (ET8) and Al(3+)-sensitive (ES8) genotypes. This current occurred more frequently, had a greater current density, and remained active for longer in ET8 protoplasts than for ES8 protoplasts. The Al(3+)-activated current exhibited higher permeability to malate(2-) than to Cl(-) (P(mal)/P(Cl)or = 2.6) and was inhibited by anion channel antagonists, niflumate and diphenylamine-2-carboxylic acid. In ET8, but not ES8, protoplasts an outward-rectifying K(+) current was activated in the presence of Al(3+) when cAMP was included in the pipette solution. These findings provide evidence that the difference in Al(3+)-induced malate efflux between Al(3+)-tolerant and Al(3+)-sensitive genotypes lies in the differing capacity for Al(3+) to activate malate permeable channels and cation channels for sustained malate release.
- Published
- 2001
49. Analysis of TaALMT1 traces the transmission of aluminum resistance in cultivated common wheat ( Triticum aestivum L.).
- Author
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Raman, Harsh, Ryan, Peter R., Raman, Rosy, Stodart, Benjamin J., Zhang, Kerong, Martin, Peter, Wood, Rachel, Sasaki, Takayuki, Yamamoto, Yoko, Mackay, Michael, Hebb, Diane M., and Delhaize, Emmanuel
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WHEAT ,PLANT germplasm ,ALUMINUM ,GENETIC polymorphisms ,MOLECULAR genetics - Abstract
Allele diversities of four markers specific to intron three, exon four and promoter regions of the aluminum (Al) resistance gene of wheat ( Triticum aestivum L.) TaALMT1 were compared in 179 common wheat cultivars used in international wheat breeding programs. In wheat cultivars released during the last 93 years, six different promoter types were identified on the basis of allele size. A previous study showed that Al resistance was not associated with a particular coding allele for TaALMT1 but was correlated with blocks of repeated sequence upstream of the coding sequence. We verified the linkage between these promoter alleles and Al resistance in three doubled haploid and one intercross populations segregating for Al resistance. Molecular and pedigree analysis suggest that Al resistance in modern wheat germplasm is derived from several independent sources. Analysis of a population of 278 landraces and subspecies of wheat showed that most of the promoter alleles associated with Al resistance pre-existed in Europe, the Middle East and Asia prior to dispersal of cultivated germplasm around the world. Furthermore, several new promoter alleles were identified among the landraces surveyed. The TaALMT1 promoter alleles found within the spelt wheats were consistent with the hypothesis that these spelts arose on several independent occasions from hybridisations between non-free-threshing tetraploid wheats and Al-resistant hexaploid bread wheats. The strong correlation between Al resistance and Al-stimulated malate efflux from the root apices of 49 diverse wheat genotypes examined was consistent with the previous finding that Al resistance in wheat is conditioned primarily by malate efflux. These results demonstrate that the markers based on intron, exon and promoter regions of TaALMT1 can trace the inheritance of the Al resistance locus within wheat pedigrees and track Al resistance in breeding programmes. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
50. A Higher Plant Δ8 Sphingolipid Desaturase with a Preference for (Z)-Isomer Formation Confers Aluminum Tolerance to Yeast and Plants[C][OA].
- Author
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Ryan, Peter R., Qing Liu, Sperling, Petra, Bei Dong, Franke, Stefan, and Delhaize, Emmanuel
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SPHINGOLIPIDS ,LIPIDS ,ALUMINUM ,SACCHAROMYCES cerevisiae ,SACCHAROMYCES - Abstract
Three plant cDNA libraries were expressed in yeast (Saccharomyces cerevisiae) and screened on agar plates containing toxic concentrations of aluminum. Nine cDNAs were isolated that enhanced the aluminum tolerance of yeast. These cDNAs were constitutively expressed in Arabidopsis (Arabidopsis thaliana) and one cDNA from the roots of Stylosanthes hamata, designated S851, conferred greater aluminum tolerance to the transgenic seedlings. The protein predicted to be encoded by S851 showed an equally high similarity to iΔ6 fatty acyl lipid desaturases and iΔ8 sphingolipid desaturases. We expressed other known Δ6 desaturase and Δ8 desaturase genes in yeast and showed that a Δ6 fatty acyl desaturase from Echium plantagineum did not confer aluminum tolerance, whereas a Δ8 sphingobase desaturase from Arabidopsis did confer aluminum tolerance. Analysis of the fatty acids and sphingobases of the transgenic yeast and plant cells demonstrated that S851 encodes a Δ8 sphingobase desaturase, which leads to the accumulation of 8(Z/E)-C
18 -phytosphingenine and 8(Z/E)-C20 -phytopshingenine in yeast and to the accumulation of 8(Z/E)-C18 -phytosphingenine in the leaves and roots of Arabidopsis plants. The newly formed 8(Z/E)-C18 -phytosphingenine in transgenic yeast accounted for 3 mol% of the total sphingobases with a 8(Z):8(E)-isomer ratio of approximately 4:1. The accumulation of 8(Z)-C18 -phytosphingenine in transgenic Arabidopsis shifted the ratio of the 8(Z):8(E) isomers from 1:4 in wild-type plants to 1:1 in transgenic plants. These results indicate that S851 encodes the first Δ8 sphingolipid desaturase to be identified in higher plants with a preference for the 8(Z)-isomer. They further demonstrate that changes in the sphingolipid composition of cell membranes can protect plants from aluminum stress. [ABSTRACT FROM AUTHOR]- Published
- 2007
- Full Text
- View/download PDF
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