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D’Alessandro A, Earley EJ, Nemkov T, Stephenson D, Dzieciatkowska M, Hansen KC, Minetti G, Champigneulle B, Stauffer E, Pichon A, Furian M, Verges S, Kleinman S, Norris PJ, Busch MP, Page GP, Kaestner L. Genetic polymorphisms and expression of Rhesus blood group RHCE are associated with 2,3-bisphosphoglycerate in humans at high altitude. Proc Natl Acad Sci U S A 2024; 121:e2315930120. [PMID: 38147558 PMCID: PMC10769835 DOI: 10.1073/pnas.2315930120] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Accepted: 10/24/2023] [Indexed: 12/28/2023] Open
Abstract
Red blood cell (RBC) metabolic reprogramming upon exposure to high altitude contributes to physiological human adaptations to hypoxia, a multifaceted process critical to health and disease. To delve into the molecular underpinnings of this phenomenon, first, we performed a multi-omics analysis of RBCs from six lowlanders after exposure to high-altitude hypoxia, with longitudinal sampling at baseline, upon ascent to 5,100 m and descent to sea level. Results highlighted an association between erythrocyte levels of 2,3-bisphosphoglycerate (BPG), an allosteric regulator of hemoglobin that favors oxygen off-loading in the face of hypoxia, and expression levels of the Rhesus blood group RHCE protein. We then expanded on these findings by measuring BPG in RBCs from 13,091 blood donors from the Recipient Epidemiology and Donor Evaluation Study. These data informed a genome-wide association study using BPG levels as a quantitative trait, which identified genetic polymorphisms in the region coding for the Rhesus blood group RHCE as critical determinants of BPG levels in erythrocytes from healthy human volunteers. Mechanistically, we suggest that the Rh group complex, which participates in the exchange of ammonium with the extracellular compartment, may contribute to intracellular alkalinization, thus favoring BPG mutase activity.
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Affiliation(s)
- Angelo D’Alessandro
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus,Aurora, CO80045
| | - Eric J. Earley
- Research Triangle Institute International, Atlanta, GA30329-4434
| | - Travis Nemkov
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus,Aurora, CO80045
| | - Daniel Stephenson
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus,Aurora, CO80045
| | - Monika Dzieciatkowska
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus,Aurora, CO80045
| | - Kirk C. Hansen
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus,Aurora, CO80045
| | - Giampaolo Minetti
- Department of Biology and Biotechnology, University of Pavia, Pavia27100, Italy
| | - Benoit Champigneulle
- Hypoxia Physiopathology laboratory (HP2), INSERM U1042, Grenoble Alpes University, Grenoble38400, France
| | - Emeric Stauffer
- Laboratoire Interuniversitaire de Biologie de la Motricité (LIBM) EA7424, Université Claude Bernard Lyon 1, Lyon69100, France
| | - Aurélien Pichon
- Université de Poitiers, Laboratoire MOVE,Poitiers20296, France
| | - Michael Furian
- Pulmonology Department, University of Zurich, Zürich 1008091, Switzerland
| | - Samuel Verges
- Hypoxia Physiopathology laboratory (HP2), INSERM U1042, Grenoble Alpes University, Grenoble38400, France
| | - Steven Kleinman
- Department of Pathology and Laborarory Medicine, University of British Columbia, Victoria, BC V6T 1Z4, Canada
| | | | | | - Grier P. Page
- Research Triangle Institute International, Atlanta, GA30329-4434
| | - Lars Kaestner
- Dynamics of Fluids, Experimental Physics, Saarland University, Saarbrücken66123, Germany
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Maniero RA, Koltun A, Vitti M, Factor BG, de Setta N, Câmara AS, Lima JE, Figueira A. Identification and functional characterization of the sugarcane ( Saccharum spp.) AMT2-type ammonium transporter ScAMT3;3 revealed a presumed role in shoot ammonium remobilization. FRONTIERS IN PLANT SCIENCE 2023; 14:1299025. [PMID: 38098795 PMCID: PMC10720369 DOI: 10.3389/fpls.2023.1299025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 11/13/2023] [Indexed: 12/17/2023]
Abstract
Sugarcane (Saccharum spp.) is an important crop for sugar and bioethanol production worldwide. To maintain and increase sugarcane yields in marginal areas, the use of nitrogen (N) fertilizers is essential, but N overuse may result in the leaching of reactive N to the natural environment. Despite the importance of N in sugarcane production, little is known about the molecular mechanisms involved in N homeostasis in this crop, particularly regarding ammonium (NH4 +), the sugarcane's preferred source of N. Here, using a sugarcane bacterial artificial chromosome (BAC) library and a series of in silico analyses, we identified an AMMONIUM TRANSPORTER (AMT) from the AMT2 subfamily, sugarcane AMMONIUM TRANSPORTER 3;3 (ScAMT3;3), which is constitutively and highly expressed in young and mature leaves. To characterize its biochemical function, we ectopically expressed ScAMT3;3 in heterologous systems (Saccharomyces cerevisiae and Arabidopsis thaliana). The complementation of triple mep mutant yeast demonstrated that ScAMT3;3 is functional for NH3/H+ cotransport at high availability of NH4 + and under physiological pH conditions. The ectopic expression of ScAMT3;3 in the Arabidopsis quadruple AMT knockout mutant restored the transport capacity of 15N-NH4 + in roots and plant growth under specific N availability conditions, confirming the role of ScAMT3;3 in NH4 + transport in planta. Our results indicate that ScAMT3;3 belongs to the low-affinity transport system (Km 270.9 µM; Vmax 209.3 µmol g-1 root DW h-1). We were able to infer that ScAMT3;3 plays a presumed role in NH4 + source-sink remobilization in the shoots via phloem loading. These findings help to shed light on the functionality of a novel AMT2-type protein and provide bases for future research focusing on the improvement of sugarcane yield and N use efficiency.
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Affiliation(s)
- Rodolfo A. Maniero
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, SP, Brazil
| | - Alessandra Koltun
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, SP, Brazil
| | - Marielle Vitti
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, SP, Brazil
| | - Bruna G. Factor
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, SP, Brazil
| | - Nathalia de Setta
- Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, São Bernardo do Campo, SP, Brazil
| | - Amanda S. Câmara
- Genebank Department, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Seeland, Germany
| | - Joni E. Lima
- Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Antonio Figueira
- Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Piracicaba, SP, Brazil
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Cao H, Liu Q, Liu X, Ma Z, Zhang J, Li X, Shen L, Yuan J, Zhang Q. Phosphatidic acid regulates ammonium uptake by interacting with AMMONIUM TRANSPORTER 1;1 in Arabidopsis. PLANT PHYSIOLOGY 2023; 193:1954-1969. [PMID: 37471275 DOI: 10.1093/plphys/kiad421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 06/26/2023] [Accepted: 06/27/2023] [Indexed: 07/22/2023]
Abstract
Ammonium (NH4+) is a key inorganic nitrogen source in cellular amino acid biosynthesis. The coupling of transcriptional and posttranslational regulation of AMMONIUM TRANSPORTER (AMT) ensures that NH4+ acquisition by plant roots is properly balanced, which allows for rapid adaptation to a variety of nitrogen conditions. Here, we report that phospholipase D (PLD)-derived phosphatidic acid (PA) interacts with AMT1;1 to mediate NH4+ uptake in Arabidopsis (Arabidopsis thaliana). We examined pldα1 pldδ-knockout mutants and found that a reduced PA level increased seedling growth under nitrogen deficiency and inhibited root growth upon NH4+ stress, which was consistent with the enhanced accumulation of cellular NH4+. PA directly bound to AMT1;1 and inhibited its transport activity. Mutation of AMT1;1 R487 to Gly (R487G) resulted in abolition of PA suppression and, subsequently, enhancement of ammonium transport activity in vitro and in vivo. Observations of AMT1;1-GFP showed suppressed endocytosis under PLD deficiency or by mutation of the PA-binding site in AMT1;1. Endocytosis was rescued by PA in the pldα1 pldδ mutant but not in the mutant AMT1;1R487G-GFP line. Together, these findings demonstrated PA-based shutoff control of plant NH4+ transport and point to a broader paradigm of lipid-transporter function.
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Affiliation(s)
- Hongwei Cao
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Qingyun Liu
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Xiao Liu
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Zhaokun Ma
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Jixiu Zhang
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Xuebing Li
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Like Shen
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Jingya Yuan
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
| | - Qun Zhang
- State Key Laboratory of Crop Genetics & Germplasm Enhancement and Utilization, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China
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Konishi N, Ma JF. Three polarly localized ammonium transporter 1 members are cooperatively responsible for ammonium uptake in rice under low ammonium condition. THE NEW PHYTOLOGIST 2021; 232:1778-1792. [PMID: 34392543 DOI: 10.1111/nph.17679] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 08/09/2021] [Indexed: 06/13/2023]
Abstract
Ammonium is a preferential nitrogen form for rice (Oryza sativa) grown in paddy field, but the molecular mechanisms for ammonium uptake have not been well understood. We functionally characterized three members belonging to ammonium transporter 1 (AMT1) and investigated their contributions to ammonium uptake. Spatial expression analysis showed that the upregulated expression of OsAMT1;1 and OsAMT1;2 and downregulated expression of OsAMT1;3 by ammonium were higher in the root mature region than in the root tips. All OsAMT1 members were polarly localized at the distal side of exodermis in the mature region of crown roots and lateral roots. Upon exposure to ammonium, localization of OsAMT1;1 and OsAMT1;2 was also observed in the endoplasmic reticulum, but their abundance in the plasma membrane was not changed. Single knockout of either gene did not affect ammonium uptake, but knockout of all three genes resulted in 95% reduction of ammonium uptake. However, the nitrogen uptake did not differ between the wild-type rice and triple mutants at high ammonium and nitrate supply. Our results indicate that three OsAMT1 members are cooperatively required for uptake of low ammonium in rice roots and that they undergo a distinct regulatory mechanism in response to ammonium.
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Affiliation(s)
- Noriyuki Konishi
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, 710-0046, Japan
| | - Jian Feng Ma
- Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, 710-0046, Japan
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Ijato T, Porras-Murillo R, Ganz P, Ludewig U, Neuhäuser B. Concentration-dependent physiological and transcriptional adaptations of wheat seedlings to ammonium. PHYSIOLOGIA PLANTARUM 2021; 171:328-342. [PMID: 32335941 DOI: 10.1111/ppl.13113] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 04/20/2020] [Indexed: 05/24/2023]
Abstract
Conventional wheat production utilizes fertilizers of various nitrogen forms. Sole ammonium nutrition has been shown to improve grain quality, despite the potential toxic effects of ammonium at elevated concentrations. We therefore investigated the responses of young seedlings of winter wheat to different nitrogen sources (NH4 NO3 = NN, NH4 Cl = NNH4 + and KNO3 = NNO3 - ). Growth with ammonium-nitrate was superior. However, an elevated concentration of sole ammonium caused severe toxicity symptoms and significant decreases in biomass accumulation. We addressed the molecular background of the ammonium uptake by gathering an overview of the ammonium transporter (AMT) of wheat (Triticum aestivum) and characterized the putative high-affinity TaAMT1 transporters. TaAMT1;1 and TaAMT1;2 were both active in yeast and Xenopus laevis oocytes and showed saturating high-affinity ammonium transport characteristics. Interestingly, nitrogen starvation, as well as ammonium resupply to starved seedlings triggered an increase in the expression of the TaAMT1s. The presence of nitrate seamlessly repressed their expression. We conclude that wheat showed the ability to respond robustly to sole ammonium supply by adopting distinct physiological and transcriptional responses.
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Affiliation(s)
- Toyosi Ijato
- Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstr. 20, 70593, Stuttgart, Germany
| | - Romano Porras-Murillo
- Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstr. 20, 70593, Stuttgart, Germany
| | - Pascal Ganz
- Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstr. 20, 70593, Stuttgart, Germany
| | - Uwe Ludewig
- Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstr. 20, 70593, Stuttgart, Germany
| | - Benjamin Neuhäuser
- Institute of Crop Science, Nutritional Crop Physiology, University of Hohenheim, Fruwirthstr. 20, 70593, Stuttgart, Germany
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Low-Dose Ammonium Preconditioning Enhances Endurance in Submaximal Physical Exercises. Sports (Basel) 2021; 9:sports9020029. [PMID: 33669436 PMCID: PMC7920466 DOI: 10.3390/sports9020029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/07/2021] [Accepted: 02/10/2021] [Indexed: 11/17/2022] Open
Abstract
Preconditioning is often used in medicine to protect organs from ischemic damage and in athletes to enhance the performances. We tested whether low-dose ammonium preconditioning (AMP) could have a beneficial effect on physical exercises (PE). We used Cardiopulmonary Exercise Testing (CPET) on a treadmill to investigate the effects of low-dose AMP on the physical exercise capacity of professional track and field athletes and tested twenty-five athletes. Because of the individual differences between athletes, we performed a preliminary treadmill test (Pre-test) and, according to the results, the athletes were randomly allocated into the AMP and control (placebo, PL) group based on the similarity of the total distance covered on a treadmill. In the AMP group, the covered distance increased (11.3 ± 3.6%, p < 0.02) compared to Pre-test. Similarly, AMP significantly increased O2 uptake volume—VO2 (4.6 ± 2.3%, p < 0.03) and pulmonary CO2 output—VCO2 (8.7 ± 2.8%, p < 0.01). Further, the basic blood parameters (pH, pO2, and lactate) shift was lower despite the greater physical exercise progress in the AMP group compared to Pre-test, whereas in the placebo group there were no differences between Pre-test and Load-test. Importantly, the AMP significantly increased red blood cell count (6.8 ± 2.0%, p < 0.01) and hemoglobin concentration (5.3 ± 1.9%, p < 0.01), which might explain the beneficial effects in physical exercise progress. For the first time, we showed that low-dose AMP had clear beneficial effects on submaximal PE.
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Ammonium Accumulation Caused by Reduced Tonoplast V-ATPase Activity in Arabidopsis thaliana. Int J Mol Sci 2020; 22:ijms22010002. [PMID: 33374906 PMCID: PMC7792577 DOI: 10.3390/ijms22010002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 12/09/2020] [Accepted: 12/10/2020] [Indexed: 01/06/2023] Open
Abstract
Plant vacuoles are unique compartments that play a critical role in plant growth and development. The vacuolar H+-ATPase (V-ATPase), together with the vacuolar H+-pyrophosphatase (V-PPase), generates the proton motive force that regulates multiple cell functions and impacts all aspects of plant life. We investigated the effect of V-ATPase activity in the vacuole on plant growth and development. We used an Arabidopsisthaliana (L.) Heynh. double mutant, vha-a2 vha-a3, which lacks two tonoplast-localized isoforms of the membrane-integral V-ATPase subunit VHA-a. The mutant is viable but exhibits impaired growth and leaf chlorosis. Nitrate assimilation led to excessive ammonium accumulation in the shoot and lower nitrogen uptake, which exacerbated growth retardation of vha-a2 vha-a3. Ion homeostasis was disturbed in plants with missing VHA-a2 and VHA-a3 genes, which might be related to limited growth. The reduced growth and excessive ammonium accumulation of the double mutant was alleviated by potassium supplementation. Our results demonstrate that plants lacking the two tonoplast-localized subunits of V-ATPase can be viable, although with defective growth caused by multiple factors, which can be alleviated by adding potassium. This study provided a new insight into the relationship between V-ATPase, growth, and ammonium accumulation, and revealed the role of potassium in mitigating ammonium toxicity.
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Lecompte M, Cattaert D, Vincent A, Birman S, Chérif-Zahar B. Drosophila ammonium transporter Rh50 is required for integrity of larval muscles and neuromuscular system. J Comp Neurol 2019; 528:81-94. [PMID: 31273786 DOI: 10.1002/cne.24742] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 05/30/2019] [Accepted: 06/21/2019] [Indexed: 12/18/2022]
Abstract
Rhesus glycoproteins (Rh50) have been shown to be ammonia transporters in many species from bacteria to human. They are involved in various physiological processes including acid excretion and pH regulation. Rh50 proteins can also provide a structural link between the cytoskeleton and the plasma membranes that maintain cellular integrity. Although ammonia plays essential roles in the nervous system, in particular at glutamatergic synapses, a potential role for Rh50 proteins at synapses has not yet been investigated. To better understand the function of these proteins in vivo, we studied the unique Rh50 gene of Drosophila melanogaster, which encodes two isoforms, Rh50A and Rh50BC. We found that Drosophila Rh50A is expressed in larval muscles and enriched in the postsynaptic regions of the glutamatergic neuromuscular junctions. Rh50 inactivation by RNA interference selectively in muscle cells caused muscular atrophy in larval stages and pupal lethality. Interestingly, Rh50-deficiency in muscles specifically increased glutamate receptor subunit IIA (GluRIIA) level and the frequency of spontaneous excitatory postsynaptic potentials. Our work therefore highlights a new role for Rh50 proteins in the maintenance of Drosophila muscle architecture and synaptic physiology, which could be conserved in other species.
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Affiliation(s)
- Mathilde Lecompte
- Genes Circuits Rhythmes et Neuropathologies, Plasticité du Cerveau, ESPCI Paris, CNRS, PSL University, Paris, France
| | - Daniel Cattaert
- Institut des Neurosciences Cognitives et Intégratives d'Aquitaine, CNRS, Bordeaux University, Bordeaux, France
| | - Alain Vincent
- Centre de Biologie du Développement, Centre de Biologie Intégrative, CNRS, Toulouse University, UPS, Toulouse, France
| | - Serge Birman
- Genes Circuits Rhythmes et Neuropathologies, Plasticité du Cerveau, ESPCI Paris, CNRS, PSL University, Paris, France
| | - Baya Chérif-Zahar
- Genes Circuits Rhythmes et Neuropathologies, Plasticité du Cerveau, ESPCI Paris, CNRS, PSL University, Paris, France
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Beier MP, Obara M, Taniai A, Sawa Y, Ishizawa J, Yoshida H, Tomita N, Yamanaka T, Ishizuka Y, Kudo S, Yoshinari A, Takeuchi S, Kojima S, Yamaya T, Hayakawa T. Lack of ACTPK1, an STY kinase, enhances ammonium uptake and use, and promotes growth of rice seedlings under sufficient external ammonium. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 93:992-1006. [PMID: 29356222 DOI: 10.1111/tpj.13824] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 12/11/2017] [Accepted: 12/15/2017] [Indexed: 05/09/2023]
Abstract
Ammonium influx into plant roots via the high-affinity transport system (HATS) is down-modulated under elevated external ammonium, preventing ammonium toxicity. In ammonium-fed Arabidopsis, ammonium transporter 1 (AMT1) trimers responsible for HATS activity are allosterically inactivated in a dose-dependent manner via phosphorylation of the conserved threonine at the carboxyl-tail by the calcineurin B-like protein 1-calcineurin B-like protein-interacting protein kinase 23 complex and other yet unidentified protein kinases. Using transcriptome and reverse genetics in ammonium-preferring rice, we revealed the role of the serine/threonine/tyrosine protein kinase gene OsACTPK1 in down-modulation of HATS under sufficient ammonium. In wild-type roots, ACTPK1 mRNA and protein accumulated dose-dependently under sufficient ammonium. To determine the function of ACTPK1, two independent mutants lacking ACTPK1 were produced by retrotransposon Tos17 insertion. Compared with segregants lacking insertions, the two mutants showed decreased root growth and increased shoot growth under 1 mm ammonium due to enhanced ammonium acquisition, via aberrantly high HATS activity, and use. Furthermore, introduction of OsACTPK1 cDNA fused to the synthetic green fluorescence protein under its own promoter complemented growth and the HATS influx, and suggested plasma membrane localization. Root cellular expression of OsACTPK1 also overlapped with that of ammonium-induced OsAMT1;1 and OsAMT1;2. Meanwhile, threonine-phosphorylated AMT1 levels were substantially decreased in roots of ACTPK1-deficient mutants grown under sufficient ammonium. Bimolecular fluorescence complementation assay further confirmed interaction between ACTPK1 and AMT1;2 at the cell plasma membrane. Overall, these findings suggest that ACTPK1 directly phosphorylates and inactivates AMT1;2 in rice seedling roots under sufficient ammonium.
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Affiliation(s)
- Marcel P Beier
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Mitsuhiro Obara
- Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi, Tsukuba, Ibaraki, 305-8686, Japan
| | - Akiko Taniai
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Yuki Sawa
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Jin Ishizawa
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Haruki Yoshida
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Narumi Tomita
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Tsuyoshi Yamanaka
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Yawara Ishizuka
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Syuko Kudo
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Akira Yoshinari
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Shiho Takeuchi
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Soichi Kojima
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Tomoyuki Yamaya
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
| | - Toshihiko Hayakawa
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, Miyagi, 981-8555, Japan
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10
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Si L, Pan L, Wang H, Zhang X. Identification of the role of Rh protein in ammonia excretion of swimming crab Portunus trituberculatus. J Exp Biol 2018; 221:jeb.184655. [DOI: 10.1242/jeb.184655] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 08/24/2018] [Indexed: 12/14/2022]
Abstract
In Portunus trituberculatus, a full-length cDNA of Rhesus-like glycoprotein (Rh protein), the whole 478 amino acids, has been identified in gills, which plays an essential role in ammonia (NH3 /NH4+) excretion. Phylogenetic analysis of the Rh-like proteins from crabs was clustered, showing high conservation of the ammonium transporter domain and transmembrane segments essential to the function of Rh protein. Rh protein of P. trituberculatus (PtRh) was detected in all tested tissues, and showed the highest expression in gills. To further characterize the role of PtRh in ammonia metabolism and excretion, a double-stranded RNA-mediated RNA interference of PtRh was employed. The knockdown of PtRh up-regulated mRNA expression of ammonia excretion related genes aquaporin (AQP), K+-channel, vesicle associated membrane protein (VAMP), increased activities of Na+ /K+ -ATPase (NKA) and V-type H+-ATPase (V-ATPase), whereas the Na+/H+-exchanger (NHE) expression reduced firstly and then elevated. dsRNA-mediated reductions in PtRh significantly reduced ammonia excretion rate and increased ammonia and glutamine (Gln) levels in hemolymph, together with increase of glutamate dehydrogenase (GDH) and glutamine synthetase (GS) activites, indicating a central role for PtRh in ammonia excretion and detoxification mechanisms. Taken together, we conclude that the Rh protein is a primary contributor to ammonia excretion of P. trituberculatus, which may be the basis of their ability to inhabit benthic water with high ammonia levels.
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Affiliation(s)
- Lingjun Si
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China
| | - Luqing Pan
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China
| | - Hongdan Wang
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China
| | - Xin Zhang
- Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, Qingdao 266003, PR China
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Giehl RFH, Laginha AM, Duan F, Rentsch D, Yuan L, von Wirén N. A Critical Role of AMT2;1 in Root-To-Shoot Translocation of Ammonium in Arabidopsis. MOLECULAR PLANT 2017; 10:1449-1460. [PMID: 29032248 DOI: 10.1016/j.molp.2017.10.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 09/01/2017] [Accepted: 10/01/2017] [Indexed: 05/24/2023]
Abstract
Ammonium uptake in plant roots is mediated by AMT/MEP/Rh-type ammonium transporters. Out of five AMTs being expressed in Arabidopsis roots, four AMT1-type transporters contribute to ammonium uptake, whereas no physiological function has so far been assigned to the only homolog belonging to the MEP subfamily, AMT2;1. Based on the observation that under ammonium supply, the transcript levels of AMT2;1 increased and its promoter activity shifted preferentially to the pericycle, we assessed the contribution of AMT2;1 to xylem loading. When exposed to 15N-labeled ammonium, amt2;1 mutant lines translocated less tracer to the shoots and contained less ammonium in the xylem sap. Moreover, in an amt1;1 amt1;2 amt1;3 amt2;1 quadruple mutant (qko), co-expression of AMT2;1 with either AMT1;2 or AMT1;3 significantly enhanced 15N translocation to shoots, indicating a cooperative action between AMT2;1 and AMT1 transporters. Under N deficiency, proAMT2;1-GFP lines showed enhanced promoter activity predominantly in cortical root cells, which coincided with elevated ammonium influx conferred by AMT2;1 at millimolar substrate concentrations. Our results indicate that in addition to contributing moderately to root uptake in the low-affinity range, AMT2;1 functions mainly in root-to-shoot translocation of ammonium, depending on its cell-type-specific expression in response to the plant nutritional status and to local ammonium gradients.
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Affiliation(s)
- Ricardo F H Giehl
- Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany
| | - Alberto M Laginha
- Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany
| | - Fengying Duan
- Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany
| | - Doris Rentsch
- Institute of Plant Sciences, University of Bern, Altenbergrain 21, 3013 Bern, Switzerland
| | - Lixing Yuan
- Key Lab of Plant-Soil Interaction, MOE, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
| | - Nicolaus von Wirén
- Department of Physiology and Cell Biology, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany.
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12
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Lupini A, Princi MP, Araniti F, Miller AJ, Sunseri F, Abenavoli MR. Physiological and molecular responses in tomato under different forms of N nutrition. JOURNAL OF PLANT PHYSIOLOGY 2017; 216:17-25. [PMID: 28551475 DOI: 10.1016/j.jplph.2017.05.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Revised: 05/16/2017] [Accepted: 05/17/2017] [Indexed: 05/14/2023]
Abstract
Urea is the most common nitrogen (N) fertilizer in agriculture, due to its cheaper price and high N content. Although the reciprocal influence between NO3- and NH4+ nutrition are well known, urea (U) interactions with these N-inorganic forms are poorly studied. Here, the responses of two tomato genotypes to ammonium nitrate (AN), U alone or in combination were investigated. Significant differences in root and shoot biomass between genotypes were observed. Under AN+U supply, Linosa showed higher biomass compared to UC82, exhibiting also higher values for many root architectural traits. Linosa showed higher Nitrogen Uptake (NUpE) and Utilization Efficiency (NUtE) compared to UC82, under AN+U nutrition. Interestingly, Linosa exhibited also a significantly higher DUR3 transcript abundance. These results underline the beneficial effect of AN+U nutrition, highlighting new molecular and physiological strategies for selecting crops that can be used for more sustainable agriculture. The data suggest that translocation and utilization (NUtE) might be a more important component of NUE than uptake (NUpE) in tomato. Genetic variation could be a source for useful NUE traits in tomato; further experiments are needed to dissect the NUtE components that confer a higher ability to utilize N in Linosa.
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Affiliation(s)
- Antonio Lupini
- Dipartimento AGRARIA, Università Mediterranea di Reggio Calabria, Feo di Vito I-89124, Reggio Calabria RC, Italy.
| | - Maria Polsia Princi
- Dipartimento AGRARIA, Università Mediterranea di Reggio Calabria, Feo di Vito I-89124, Reggio Calabria RC, Italy
| | - Fabrizio Araniti
- Dipartimento AGRARIA, Università Mediterranea di Reggio Calabria, Feo di Vito I-89124, Reggio Calabria RC, Italy
| | | | - Francesco Sunseri
- Dipartimento AGRARIA, Università Mediterranea di Reggio Calabria, Feo di Vito I-89124, Reggio Calabria RC, Italy
| | - Maria Rosa Abenavoli
- Dipartimento AGRARIA, Università Mediterranea di Reggio Calabria, Feo di Vito I-89124, Reggio Calabria RC, Italy
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13
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Nath M, Tuteja N. NPKS uptake, sensing, and signaling and miRNAs in plant nutrient stress. PROTOPLASMA 2016; 253:767-786. [PMID: 26085375 DOI: 10.1007/s00709-015-0845-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2015] [Accepted: 06/08/2015] [Indexed: 05/24/2023]
Abstract
Sessile nature of higher plants consequently makes it highly adaptable for nutrient absorption and acquisition from soil. Plants require 17 essential elements for their growth and development which include 14 minerals (macronutrients: N, P, K, Mg, Ca, S; micronutrients: Cl, Fe, B, Mn, Zn, Cu, Ni, Mo) and 3 non-mineral (C, H, O) elements. The roots of higher plants must acquire these macronutrients and micronutrients from rhizosphere and further allocate to other plant parts for completing their life cycle. Plants evolved an intricate series of signaling and sensing cascades to maintain nutrient homeostasis and to cope with nutrient stress/availability. The specific receptors for nutrients in root, root system architecture, and internal signaling pathways help to develop plasticity in response to the nutrient starvation. Nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) are essential for various metabolic processes, and their deficiency negatively effects the plant growth and yield. Genes coding for transporters and receptors for nutrients as well as some small non-coding RNAs have been implicated in nutrient uptake and signaling. This review summarizes the N, P, K, and S uptake, sensing and signaling events in nutrient stress condition especially in model plant Arabidopsis thaliana and involvement of microRNAs in nutrient deficiency. This article also provides a framework of uptake, sensing, signaling and to highlight the microRNA as an emerging major players in nutrient stress condition. Nutrient-plant-miRNA cross talk may help plant to cope up nutrient stress, and understanding their precise mechanism(s) will be necessary to develop high yielding smart crop with low nutrient input.
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Affiliation(s)
- Manoj Nath
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, 110067, New Delhi, India
| | - Narendra Tuteja
- Plant Molecular Biology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, 110067, New Delhi, India.
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14
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Vigna subterranea ammonium transporter gene ( VsAMT1): Some bioinformatics insights. BIOTECHNOLOGY REPORTS (AMSTERDAM, NETHERLANDS) 2015; 8:88-93. [PMID: 28352577 PMCID: PMC4980749 DOI: 10.1016/j.btre.2015.10.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 09/22/2015] [Accepted: 10/08/2015] [Indexed: 12/11/2022]
Abstract
Ammonium transporters (AMTs) play a role in the uptake of ammonium, the form in which nitrogen is preferentially absorbed by plants. Vigna subterranea (VsAMT1) and Solanum tuberosum (StAMT1) AMT1s were characterized using molecular biology and bioinformatics methods. AMT1-specific primers were designed and used to amplify the AMT1 internal regions. Nucleotide sequencing, alignment and phylogenetic analysis assigned VsAMT1 and StAMT1 to the AMT1 family. The deduced amino acid sequences showed that VsAMT1 is 92% and 89% similar to Phaseolus vulgaris PvAMT1.1 and Glycine max AMT1 respectively, while StAMT1 is 92% similar to Solanum lycopersicum LeAMT1.1, and correspond to the 5th–10th trans-membrane domains. Residues VsAMT1 D23 and StAMT1 D15 are predicted to be essential for ammonium transport, while mutations of VsAMT1 W1A-L and S87A and StAMT1 S76A may further enhance ammonium transport. In addition to nitrogen uptake from the roots, VsAMT1 may also contribute to interactions with rhizobia.
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15
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Neuhäuser B, Dynowski M, Ludewig U. Switching substrate specificity of AMT/MEP/ Rh proteins. Channels (Austin) 2015; 8:496-502. [PMID: 25483282 DOI: 10.4161/19336950.2014.967618] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In organisms from all kingdoms of life, ammonia and its conjugated ion ammonium are transported across membranes by proteins of the AMT/Rh family. Efficient and successful growth often depends on sufficient ammonium nutrition. The proteins mediating this transport, the so called Ammonium Transporter (AMT) or Rhesus like (Rh) proteins, share a very similar trimeric overall structure and a high sequence similarity even throughout the kingdoms. Even though structural components of the transport mechanism, like an external substrate recruitment site, an essential twin histidine pore motif, a phenylalanine gate and the hydrophobic pore are strongly conserved and have been analyzed in detail by molecular dynamic simulations and mutational studies, the substrate(s), which pass the central pores of the AMT/Rh subunits, NH4(+), NH3 + H(+), NH4(+) + H(+) or NH3, are still a matter of debate for most proteins, including the best characterized AmtB protein from Escherichia coli. The lack of a robust expression system for functional analysis has hampered proof of structural and mutational studies, although the NH3 transport function for Rh-like proteins is rarely disputed. In plant transporters belonging to the subfamily AMT1, transport is associated with electrical currents, while some plant transporters, notably of the AMT2 type, were suggested to transport NH3 across the membrane, without associated ionic currents. Here we summarize data in favor of each substrate for the distinct AMT/Rh classes, discuss mutants and how they differ in structure and functionality. A common mechanism with deprotonation and subsequent NH3 transport through the central subunit pore is suggested.
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Affiliation(s)
- Benjamin Neuhäuser
- a Institute of Crop Science; Nutritional Crop Physiology ; University of Hohenheim ; Stuttgart , Germany
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16
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Larsen EH, Deaton LE, Onken H, O'Donnell M, Grosell M, Dantzler WH, Weihrauch D. Osmoregulation and Excretion. Compr Physiol 2014; 4:405-573. [DOI: 10.1002/cphy.c130004] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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17
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Ullmann RT, Andrade SLA, Ullmann GM. Thermodynamics of transport through the ammonium transporter Amt-1 investigated with free energy calculations. J Phys Chem B 2012; 116:9690-703. [PMID: 22804733 DOI: 10.1021/jp305440f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Amt-1 from Archaeoglobus fulgidus (AfAmt-1) belongs to the Amt/Rh family of ammonium/ammonia transporting membrane proteins. The transport mode and the precise microscopic permeation mechanism utilized by these proteins are intensely debated. Open questions concern the identity of the transported substrate (ammonia and/or ammonium) and whether the transport is passive or active. To address these questions, we studied the overall thermodynamics of the different transport modes as a function of the environmental conditions. Then, we investigated the thermodynamics of the underlying microscopic transport mechanisms with free energy calculations within a continuum electrostatics model. The formalism developed for this purpose is of general utility in the calculation of binding free energies for ligands with multiple protonation forms or other binding forms. The results of our calculations are compared to the available experimental and theoretical data on Amt/Rh proteins and discussed in light of the current knowledge on the physiological conditions experienced by microorganisms and plants. We found that microscopic models of electroneutral and electrogenic transport modes are in principle thermodynamically viable. However, only the electrogenic variants have a net thermodynamic driving force under the physiological conditions experienced by microorganisms and plants. Thus, the transport mechanism of AfAmt-1 is most likely electrogenic.
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Affiliation(s)
- R Thomas Ullmann
- Structural Biology/Bioinformatics, University of Bayreuth, Universitätsstrasse 30, BGI, 95447 Bayreuth, Germany.
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18
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De Michele R, Loqué D, Lalonde S, Frommer WB. Ammonium and urea transporter inventory of the selaginella and physcomitrella genomes. FRONTIERS IN PLANT SCIENCE 2012; 3:62. [PMID: 22639655 PMCID: PMC3355718 DOI: 10.3389/fpls.2012.00062] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 03/14/2012] [Indexed: 05/05/2023]
Abstract
Ammonium and urea are important nitrogen sources for autotrophic organisms. Plant genomes encode several families of specific transporters for these molecules, plus other uptake mechanisms such as aquaporins and ABC transporters. Selaginella and Physcomitrella are representatives of lycophytes and bryophytes, respectively, and the recent completion of their genome sequences provided us with an opportunity for comparative genome studies, with special emphasis on the adaptive processes that accompanied the conquest of dry land and the evolution of a vascular system. Our phylogenetic analysis revealed that the number of genes encoding urea transporters underwent a progressive reduction during evolution, eventually down to a single copy in vascular plants. Conversely, no clear evolutionary pattern was found for ammonium transporters, and their number and distribution in families varies between species. In particular Selaginella, similar to rice, favors the AMT2/MEP family of ammonium transporters over the plant-specific AMT1 type. In comparison, Physcomitrella presents several members belonging to both families.
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Affiliation(s)
- Roberto De Michele
- Department of Plant Biology, Carnegie Institution for ScienceStanford, CA, USA
- Plant Genetics Institute, National Research Council of ItalyPalermo, Italy
| | | | - Sylvie Lalonde
- Department of Plant Biology, Carnegie Institution for ScienceStanford, CA, USA
| | - Wolf B. Frommer
- Department of Plant Biology, Carnegie Institution for ScienceStanford, CA, USA
- *Correspondence: Wolf B. Frommer, Department of Plant Biology, Carnegie Institution for Science, 260 Panama Street, Stanford, CA 94305, USA. e-mail:
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19
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Graff L, Obrdlik P, Yuan L, Loqué D, Frommer WB, von Wirén N. N-terminal cysteines affect oligomer stability of the allosterically regulated ammonium transporter LeAMT1;1. JOURNAL OF EXPERIMENTAL BOTANY 2011; 62:1361-73. [PMID: 21127027 DOI: 10.1093/jxb/erq379] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
AMMONIUM TRANSPORTER (AMT) proteins are conserved in all domains of life and mediate the transport of ammonium or ammonia across cell membranes. AMTs form trimers and use intermolecular interaction between subunits to regulate activity. So far, binding forces that stabilize AMT protein complexes are not well characterized. High temperature or reducing agents released mono- and dimeric forms from trimeric complexes formed by AMT1;1 from Arabidopsis and tomato. However, in the paralogue LeAMT1;3, trimeric complexes were not detected. LeAMT1;3 differs from the other AMTs by an unusually short N-terminus, suggesting a role for the N-terminus in oligomer stability. Truncation of the N-terminus in LeAMT1;1 destabilized the trimer and led to loss of functionality when expressed in yeast. Swapping of the N-terminus between LeAMT1;1 and LeAMT1;3 showed that sequences in the N-terminus of LeAMT1;1 are necessary and sufficient for stabilization of the interaction among the subunits. Two N-terminal cysteine residues are highly conserved among AMT1 transporters in plants but are lacking in LeAMT1;3. C3S or C27S variants of LeAMT1;1 showed reduced complex stability, which coincided with lower transport capacity for the substrate analogue methylammonium. Both cysteine-substituted LeAMT1;1 variants showed weaker interactions with the wildtype as determined by a quantitative analysis of the complex stability using the mating-based split-ubiquitin assay. These data indicate that the binding affinity of AMT1 subunits is stabilized by cysteines in the N-terminus and suggest a role for disulphide bridge formation via apoplastic N-terminal cysteine residues.
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Affiliation(s)
- Lucile Graff
- Institute for Plant Nutrition, University of Hohenheim, D-70593 Stuttgart, Germany
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20
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Barth C, Gouzd ZA, Steele HP, Imperio RM. A mutation in GDP-mannose pyrophosphorylase causes conditional hypersensitivity to ammonium, resulting in Arabidopsis root growth inhibition, altered ammonium metabolism, and hormone homeostasis. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:379-94. [PMID: 20007685 PMCID: PMC2803207 DOI: 10.1093/jxb/erp310] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2009] [Revised: 09/29/2009] [Accepted: 10/01/2009] [Indexed: 05/17/2023]
Abstract
Ascorbic acid (AA) is an antioxidant fulfilling a multitude of cellular functions. Given its pivotal role in maintaining the rate of cell growth and division in the quiescent centre of the root, it was hypothesized that the AA-deficient Arabidopsis thaliana mutants vtc1-1, vtc2-1, vtc3-1, and vtc4-1 have altered root growth. To test this hypothesis, root development was studied in the wild type and vtc mutants grown on Murashige and Skoog medium. It was discovered, however, that only the vtc1-1 mutant has strongly retarded root growth, while the other vtc mutants exhibit a wild-type root phenotype. It is demonstrated that the short-root phenotype in vtc1-1 is independent of AA deficiency and oxidative stress. Instead, vtc1-1 is conditionally hypersensitive to ammonium (NH(4)(+)). To provide new insights into the mechanism of NH(4)(+) sensitivity in vtc1-1, root development, NH(4)(+) content, glutamine synthetase (GS) activity, glutamate dehydrogenase activity, and glutamine content were assessed in wild-type and vtc1-1 mutant plants grown in the presence and absence of high NH(4)(+) and the GS inhibitor MSO. Since VTC1 encodes a GDP-mannose pyrophosphorylase, an enzyme generating GDP-mannose for AA biosynthesis and protein N-glycosylation, it was also tested whether protein N-glycosylation is affected in vtc1-1. Furthermore, since root development requires the action of a variety of hormones, it was investigated whether hormone homeostasis is linked to NH(4)(+) sensitivity in vtc1-1. Our data suggest that NH(4)(+) hypersensitivity in vtc1-1 is caused by disturbed N-glycosylation and that it is associated with auxin and ethylene homeostasis and/or nitric oxide signalling.
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Affiliation(s)
- Carina Barth
- Department of Biology, West Virginia University, 53 Campus Drive, Morgantown, WV 26506-6507, USA.
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21
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Garnett T, Conn V, Kaiser BN. Root based approaches to improving nitrogen use efficiency in plants. PLANT, CELL & ENVIRONMENT 2009; 32:1272-83. [PMID: 19558408 DOI: 10.1111/j.1365-3040.2009.02011.x] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
In the majority of agricultural growing regions, crop production is highly dependent on the supply of exogenous nitrogen (N) fertilizers. Traditionally, this dependency and the use of N-fertilizers to restore N depleted soils has been rewarded with increased plant health and yields. In recent years, increased competition for non-renewable fossil fuel reserves has directly elevated prices of N-fertilizers and the cost of agricultural production worldwide. Furthermore, N-fertilizer based pollution is becoming a serious issue for many regions where agriculture is highly concentrated. To help minimize the N footprint associated with agricultural production there is significant interest at the plant level to develop technologies which can allow economically viable production while using less applied N. To complement recent reviews examining N utilization efficiency in agricultural plants, this review will explore those strategies operating specifically at the root level, which may directly contribute to improved N use efficiencies in agricultural crops such as cereals, where the majority of N-fertilizers are used and lost to the environment. Root specific phenotypes that will be addressed in the context of improvements to N acquisition and assimilation efficiencies include: root morphology; root to shoot ratios; root vigour, root length density; and root N transport and metabolism.
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Affiliation(s)
- Trevor Garnett
- School of Agriculture Food and Wine, The University of Adelaide, Urrbrae, SA 5064, Australia
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22
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Yuan L, Loqué D, Kojima S, Rauch S, Ishiyama K, Inoue E, Takahashi H, von Wirén N. The organization of high-affinity ammonium uptake in Arabidopsis roots depends on the spatial arrangement and biochemical properties of AMT1-type transporters. THE PLANT CELL 2007; 19:2636-52. [PMID: 17693533 PMCID: PMC2002620 DOI: 10.1105/tpc.107.052134] [Citation(s) in RCA: 227] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The AMMONIUM TRANSPORTER (AMT) family comprises six isoforms in Arabidopsis thaliana. Here, we describe the complete functional organization of root-expressed AMTs for high-affinity ammonium uptake. High-affinity influx of (15)N-labeled ammonium in two transposon-tagged amt1;2 lines was reduced by 18 to 26% compared with wild-type plants. Enrichment of the AMT1;2 protein in the plasma membrane and localization of AMT1;2 promoter activity in the endodermis and root cortex indicated that AMT1;2 mediates the uptake of ammonium entering the root via the apoplasmic transport route. An amt1;1 amt1;2 amt1;3 amt2;1 quadruple mutant (qko) showed severe growth depression under ammonium supply and maintained only 5 to 10% of wild-type high-affinity ammonium uptake capacity. Transcriptional upregulation of AMT1;5 in nitrogen-deficient rhizodermal and root hair cells and the ability of AMT1;5 to transport ammonium in yeast suggested that AMT1;5 accounts for the remaining uptake capacity in qko. Triple and quadruple amt insertion lines revealed in vivo ammonium substrate affinities of 50, 234, 61, and 4.5 muM for AMT1;1, AMT1;2, AMT1;3, and AMT1;5, respectively, but no ammonium influx activity for AMT2;1. These data suggest that two principle means of achieving effective ammonium uptake in Arabidopsis roots are the spatial arrangement of AMT1-type ammonium transporters and the distribution of their transport capacities at different substrate affinities.
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Affiliation(s)
- Lixing Yuan
- Molecular Plant Nutrition, Institute of Plant Nutrition, University of Hohenheim, D-70593 Stuttgart, Germany
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23
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Neuhäuser B, Dynowski M, Mayer M, Ludewig U. Regulation of NH4+ transport by essential cross talk between AMT monomers through the carboxyl tails. PLANT PHYSIOLOGY 2007; 143:1651-9. [PMID: 17337531 PMCID: PMC1851830 DOI: 10.1104/pp.106.094243] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Ammonium transport across plant plasma membranes is facilitated by AMT/Rh-type ammonium transporters (AMTs), which also have homologs in most organisms. In the roots of the plant Arabidopsis (Arabidopsis thaliana), AMTs have been identified that function directly in the high-affinity NH4+ acquisition from soil. Here, we show that AtAMT1;2 has a distinct role, as it is located in the plasma membrane of the root endodermis. AtAMT1;2 functions as a comparatively low-affinity NH4+ transporter. Mutations at the highly conserved carboxyl terminus (C terminus) of AMTs, including one that mimics phosphorylation at a putative phosphorylation site, impair NH4+ transport activity. Coexpressing these mutants along with wild-type AtAMT1;2 substantially reduced the activity of the wild-type transporter. A molecular model of AtAMT1;2 provides a plausible explanation for the dominant inhibition, as the C terminus of one monomer directly contacts the neighboring subunit. It is suggested that part of the cytoplasmic C terminus of a single monomer can gate the AMT trimer. This regulatory mechanism for rapid and efficient inactivation of NH4+ transporters may apply to several AMT members to prevent excess influx of cytotoxic ammonium.
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Affiliation(s)
- Benjamin Neuhäuser
- Zentrum für Molekularbiologie der Pflanzen, Pflanzenphysiologie, Universität Tübingen, D-72076 Tuebingen, Germany
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24
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Luzhkov VB, Almlöf M, Nervall M, Aqvist J. Computational study of the binding affinity and selectivity of the bacterial ammonium transporter AmtB. Biochemistry 2006; 45:10807-14. [PMID: 16953566 DOI: 10.1021/bi0610799] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report results from microscopic molecular dynamics and free energy perturbation simulations of substrate binding and selectivity for the Escherichia coli high-affinity ammonium transporter AmtB. The simulation system consists of the protein embedded in a model membrane/water surrounding. The calculated absolute binding free energies for the external NH(4)(+) ions are between -5.8 and -7.3 kcal/mol and are in close agreement with experimental data. The apparent pK(a) of the bound NH(4)(+) increases by more than 4 units, indicating a preference for binding ammonium ion and not neutral ammonia. The external binding site is also selective for NH(4)(+) toward monovalent metal cations by 2.4-4.4 kcal/mol. The externally bound NH(4)(+) shows strong electrostatic interactions with the proximal buried Asp160, stabilized in the anionic form, whereas the interactions with the aromatic rings of Phe107 and Trp148, lining the binding cavity, are less pronounced. Simulated mutation of the highly conserved Asp160 to Asn reduces the pK(a) of the bound ammonium ion by approximately 7 units and causes loss of its binding. The calculations further predict that the substrate affinity of E. coli AmtB depends on the ionization state of external histidines. The computed free energies of hypothetical intermediate states related to transfer of NH(3), NH(4)(+), or H(2)O from the external binding site to the first position inside the internal channel pore favor permeation of the neutral species through the channel interior. However, the predicted change in the apparent pK(a) of NH(4)(+) upon translocation from the external site, Am1, to the first internal site, Am2, indicates that ammonium ion becomes deprotonated only when it enters the channel interior.
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Affiliation(s)
- Victor B Luzhkov
- Department of Cell and Molecular Biology, Uppsala University, BMC, Box 596, S-751 24 Uppsala, Sweden.
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25
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Abstract
AMT (ammonium transporter)/Rh (Rhesus) ammonium transporters/channels are identified in all domains of life and fulfil contrasting functions related either to ammonium acquisition or excretion. Based on functional and crystallographic high-resolution structural data, it was recently proposed that the bacterial AmtB (ammonium transporter B) is a gas channel for NH3 [Khademi, O'Connell, III, Remis, Robles-Colmenares, Miercke and Stroud (2004) Science 305, 1587-1594; Zheng, Kostrewa, Berneche, Winkler and Li (2004) Proc. Natl. Acad. Sci. U.S.A. 101, 17090-17095]. Key residues, proposed to be crucial for NH3 conduction, and the hydrophobic, but obstructed, pore were conserved in a homology model of LeAMT1;1 from tomato. Transport by LeAMT1;1 was affected by mutations of residues that were predicted to constitute the aromatic recruitment site for NH4+ at the external pore entrance. Despite the structural similarities, LeAMT1;1 was shown to transport only the ion; each transported 14C-methylammonium molecule carried a single positive elementary charge. Similarly, NH4+ (or H+/NH3) was transported, but NH3 conduction was excluded. It is concluded that related proteins and a similar molecular architecture can apparently support contrasting transport mechanisms.
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Affiliation(s)
- Maria Mayer
- Zentrum für Molekularbiologie der Pflanzen (ZMBP), Pflanzenphysiologie, Universität Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
| | - Marek Dynowski
- Zentrum für Molekularbiologie der Pflanzen (ZMBP), Pflanzenphysiologie, Universität Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
| | - Uwe Ludewig
- Zentrum für Molekularbiologie der Pflanzen (ZMBP), Pflanzenphysiologie, Universität Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
- To whom correspondence should be addressed (email )
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Ji Q, Hashmi S, Liu Z, Zhang J, Chen Y, Huang CH. CeRh1 (rhr-1) is a dominant Rhesus gene essential for embryonic development and hypodermal function in Caenorhabditis elegans. Proc Natl Acad Sci U S A 2006; 103:5881-6. [PMID: 16595629 PMCID: PMC1458667 DOI: 10.1073/pnas.0600901103] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Indexed: 01/16/2023] Open
Abstract
Rhesus (Rh) proteins share a conserved 12-transmembrane topology and specify a family of putative CO(2) channels found in diverse species from microbes to human, but their functional essentiality and physiological importance in metazoans is unknown. To address this key issue and analyze Rh-engaged physiologic processes, we sought to explore model organisms with fewer Rh genes yet are tractable to genetic manipulations. In this article, we describe the identification in nematodes of two Rh homologues that are highly conserved and similar to human Rh glycoproteins, and we focus on their characterization in Caenorhabditis elegans. RNA analysis revealed that CeRh1 is abundantly expressed in all developmental stages, with highest levels in adults, whereas CeRh2 shows a differential and much lower expression pattern. In transient expression in human cells, both CeRh1 and CeRh2-GFP fusion proteins were routed to the plasma membrane. Transgenic analysis with GFP or LacZ-fusion reporters showed that CeRh1 is mainly expressed in hypodermal tissue, although it is also in other cell types. Mutagenesis analysis using deletion constructs mapped a minimal promoter region driving CeRh1 gene expression. Although CeRh2 was dispensable, RNA interference with CeRh1 caused a lethal phenotype mainly affecting late stages of C. elegans embryonic development, which could be rescued by the CbRh1 homologue from the worm Caenorhabditis briggsae. Taken together, our data provide direct evidence for the essentiality of the CeRh1 gene in C. elegans, establishing a useful animal model for investigating CO(2) channel function by cross-species complementation.
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Affiliation(s)
- Qiongmei Ji
- Laboratories of *Biochemistry and Molecular Genetics
| | - Sarwar Hashmi
- Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, 310 East 67th Street, New York, NY 10021
| | - Zhi Liu
- Laboratories of *Biochemistry and Molecular Genetics
| | - Jun Zhang
- Molecular Parasitology, Lindsley F. Kimball Research Institute, New York Blood Center, 310 East 67th Street, New York, NY 10021
| | - Ying Chen
- Laboratories of *Biochemistry and Molecular Genetics
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Mayer M, Schaaf G, Mouro I, Lopez C, Colin Y, Neumann P, Cartron JP, Ludewig U. Different transport mechanisms in plant and human AMT/Rh-type ammonium transporters. ACTA ACUST UNITED AC 2006; 127:133-44. [PMID: 16446503 PMCID: PMC2151487 DOI: 10.1085/jgp.200509369] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The conserved family of AMT/Rh proteins facilitates ammonium transport across animal, plant, and microbial membranes. A bacterial homologue, AmtB, forms a channel-like structure and appears to function as an NH3 gas channel. To evaluate the function of eukaryotic homologues, the human RhCG glycoprotein and the tomato plant ammonium transporter LeAMT1;2 were expressed and compared in Xenopus oocytes and yeast. RhCG mediated the electroneutral transport of methylammonium (MeA), which saturated with Km = 3.8 mM at pHo 7.5. Uptake was strongly favored by increasing the pHo and was inhibited by ammonium. Ammonium induced rapid cytosolic alkalinization in RhCG-expressing oocytes. Additionally, RhCG expression was associated with an alkali-cation conductance, which was not significantly permeable to NH4+ and was apparently uncoupled from the ammonium transport. In contrast, expression of the homologous LeAMT1;2 induced pHo-independent MeA+ uptake and specific NH4+ and MeA+ currents that were distinct from endogenous currents. The different mechanisms of transport, including the RhCG-associated alkali-cation conductance, were verified by heterologous expression in appropriate yeast strains. Thus, homologous AMT/Rh-type proteins function in a distinct manner; while LeAMT1;2 carries specifically NH4+, or cotransports NH3/H+, RhCG mediates electroneutral NH3 transport.
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Affiliation(s)
- Maria Mayer
- Zentrum für Molekularbiologie der Pflanzen, Pflanzenphysiologie, Universität Tübingen, Tübingen, Germany
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28
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Abstract
The structure determination of the ammonium transport protein AmtB from Escherichia coli strongly indicates that the members of the ubiquitous ammonium transporter/methylamine permease/Rhesus (Amt/MEP/Rh) protein family are ammonia-conducting channels rather than ammonium ion transporters. The most conserved part of these proteins, apart from the common overall structure with 11 transmembrane helices, is the pore lined by hydrophobic side chains except for two highly conserved histidine residues. A high-affinity ion-binding site specific for ammonium is present at the extracellular pore entry of the Amt/MEP proteins. It is proposed to play an important role in enhancing net transport at very low external ammonium concentrations and to provide discrimination against water. The site is not conserved in the animal Rhesus proteins which are implicated in ammonium homeostasis and saturate at millimolar ammonium concentrations. Many aspects of the biological function of these ammonia channels are still poorly understood and further studies in cellular systems are needed. Likewise, studies with purified, reconstituted Amt/MEP/Rh proteins will be needed to resolve open mechanistic questions and gain a more quantitative understanding of the conduction mechanism in general and for different subfamily representatives.
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Affiliation(s)
- Fritz K Winkler
- Structural Biology, Biomolecular Research, Paul Scherrer Institut, 5232 Villigen, Switzerland.
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Zheng L, Kostrewa D, Bernèche S, Winkler FK, Li XD. The mechanism of ammonia transport based on the crystal structure of AmtB of Escherichia coli. Proc Natl Acad Sci U S A 2004; 101:17090-5. [PMID: 15563598 PMCID: PMC535379 DOI: 10.1073/pnas.0406475101] [Citation(s) in RCA: 263] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Indexed: 11/18/2022] Open
Abstract
Ammonium is one of the most important nitrogen sources for bacteria, fungi, and plants, but it is toxic to animals. The ammonium transport proteins (methylamine permeases/ammonium transporters/rhesus) are present in all domains of life; however, functional studies with members of this family have yielded controversial results with respect to the chemical identity (NH(4)(+) or NH(3)) of the transported species. We have solved the structure of wild-type AmtB from Escherichia coli in two crystal forms at 1.8- and 2.1-A resolution, respectively. Substrate transport occurs through a narrow mainly hydrophobic pore located at the center of each monomer of the trimeric AmtB. At the periplasmic entry, a binding site for NH(4)(+) is observed. Two phenylalanine side chains (F107 and F215) block access into the pore from the periplasmic side. Further into the pore, the side chains of two highly conserved histidine residues (H168 and H318) bridged by a H-bond lie adjacent, with their edges pointing into the cavity. These histidine residues may facilitate the deprotonation of an ammonium ion entering the pore. Adiabatic free energy calculations support the hypothesis that an electrostatic barrier between H168 and H318 hinders the permeation of cations but not that of the uncharged NH(3.) The structural data and energetic considerations strongly indicate that the methylamine permeases/ammonium transporters/rhesus proteins are ammonia gas channels. Interestingly, at the cytoplasmic exit of the pore, two different conformational states are observed that might be related to the inactivation mechanism by its regulatory partner.
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Affiliation(s)
- Lei Zheng
- Biomolecular Research, Paul Scherrer Institut, CH-5232, Villigen, Switzerland
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30
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Abstract
The liver and kidney are important tissues for ammonium (NH4+/NH3) metabolism and excretion. The rhesus B glycoprotein (RhBG) is a membrane protein expressed in liver and kidney with similarity to NH4+ transporters found in microorganisms, plants and animals. In the kidney, RhBG is predominantly localized to basolateral membranes of distal tubule epithelia, including connecting tubules and collecting ducts. These epithelia display mainly electroneutral ammonium transport, in contrast to other tubular sites, where net NH4+ transport occurs. In accordance with its localization, human RhBG mediates saturable, electroneutral transport of the ammonium analogue methylammonium when heterologously expressed in Xenopus oocytes. Uptake of methylammonium saturates with a Km = 2.6 mm. Methylammonium uptake is inhibited by ammonium and this inhibition saturates with a Ki approximately 3 mm. Electric current measurements and intracellular pHi determinations suggest that RhBG acts as an electroneutral NH4+ -H+ exchanger.
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Affiliation(s)
- Uwe Ludewig
- Pflanzenphysiologie, Zentrum für Molekularbiologie der Pflanzen, Universität Tübingen, Auf der Morgenstelle 1, D-72076, Germany.
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Wirén NV, Merrick M. Regulation and function of ammonium carriers in bacteria, fungi, and plants. MOLECULAR MECHANISMS CONTROLLING TRANSMEMBRANE TRANSPORT 2004. [DOI: 10.1007/b95775] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Ludewig U, Wilken S, Wu B, Jost W, Obrdlik P, El Bakkoury M, Marini AM, André B, Hamacher T, Boles E, von Wirén N, Frommer WB. Homo- and hetero-oligomerization of ammonium transporter-1 NH4 uniporters. J Biol Chem 2003; 278:45603-10. [PMID: 12952951 DOI: 10.1074/jbc.m307424200] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In most organisms, high affinity ammonium uptake is catalyzed by members of the ammonium transporter family (AMT/MEP/Rh). A single point mutation (G458D) in the cytosolic C terminus of the plasma membrane transporter LeAMT1;1 from tomato leads to loss of function, although mutant and wild type proteins show similar localization when expressed in yeast or plant protoplasts. Co-expression of LeAMT1;1 and mutant in Xenopus oocytes inhibited ammonium transport in a dominant negative manner, suggesting homo-oligomerization. In vivo interaction between LeAMT1;1 proteins was confirmed by the split ubiquitin yeast two-hybrid system. LeAMT1;1 is isolated from root membranes as a high molecular mass oligomer, converted to a approximately 35-kDa polypeptide by denaturation. To investigate interactions with the LeAMT1;2 paralog, co-localizing with LeAMT1;1 in root hairs, LeAMT1;2 was characterized as a lower affinity NH4+ uniporter. Co-expression of wild types with the respective G458D/G465D mutants inhibited ammonium transport in a dominant negative manner, supporting the formation of heteromeric complexes in oocytes. Thus, in yeast, oocytes, and plants, ammonium transporters are able to oligomerize, which may be relevant for regulation of ammonium uptake.
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Affiliation(s)
- Uwe Ludewig
- Zentrum für Molekularbiologie der Pflanzen, Pflanzenphysiologie, Universität Tübingen, Auf der Morgenstelle 1, 72076 Tübingen, Germany
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Hemker MB, Cheroutre G, van Zwieten R, Maaskant-van Wijk PA, Roos D, Loos JA, van der Schoot CE, von dem Borne AEGK. The Rh complex exports ammonium from human red blood cells. Br J Haematol 2003; 122:333-40. [PMID: 12846905 DOI: 10.1046/j.1365-2141.2003.04425.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Rh blood group system represents a major immunodominant protein complex on red blood cells (RBC). Recently, the Rh homologues RhAG and RhCG were shown to promote ammonium ion transport in yeast. In this study, we showed that also in RBC the human Rh complex functions as an exporter of ammonium ions. We measured ammonium import during the incubation of RBC in a solution containing a radiolabelled analogue of NH4Cl (14C-methyl-NH3Cl). Rhnull cells of the regulator type (expressing no Rh complex proteins) accumulated significantly higher levels (P = 0.05) of radiolabelled methyl-ammonium ions than normal RBC, at room temperature. Rhnull cells of the amorph type (expressing limited amounts of Rh complex proteins) accumulated an intermediate amount of methyl-ammonium ions. To show that decreased ammonium export contributes to its accumulation, the release of intracellular methyl-ammonium from the cells was measured over time. In 30 s, normal RBC released 87% of the intracellular methyl-ammonium ions, whereas Rhnull cells of the regulator type released only 46%. We conclude that the Rh complex is involved in the export of ammonium from RBC.
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Affiliation(s)
- Mirte B Hemker
- Laboratory for Transfusion Science, Bloodbank Rotterdam, Rotterdam, the Netherlands
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34
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Sonoda Y, Ikeda A, Saiki S, von Wirén N, Yamaya T, Yamaguchi J. Distinct expression and function of three ammonium transporter genes (OsAMT1;1-1;3) in rice. PLANT & CELL PHYSIOLOGY 2003; 44:726-34. [PMID: 12881500 DOI: 10.1093/pcp/pcg083] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
To study the regulation of ammonium uptake into rice roots, three ammonium transporter genes (OsAMT1;1, 1;2 and 1;3; Oryza sativa ammonium transporter) were isolated and examined. OsAMT1s belong to AMT1 family, containing 11 putative transmembrane-spanning domains. Southern blot analysis and screening of the rice genome database confirmed that with OsAMT1;1-1;3 the complete AMT1 family of rice had been isolated. Heterologous expression of OsAMT1s in the yeast Saccharomyces cerevisiae mutant 31019b showed that all three OsAMT1s exhibit ammonium transport activity. Northern blot analysis showed a distinct expression pattern for the three genes; more constitutive expression in shoots and roots for OsAMT1;1, root-specific and ammonium-inducible expression for OsAMT1;2, and root-specific and nitrogen-derepressible expression for OsAMT1;3. In situ mRNA detection revealed that OsAMT1;2 is expressed in the central cylinder and cell surface of root tips. This gene expression analysis revealed a distinct nitrogen-dependent regulation for AMTs in rice, differing from that in tomato or Arabidopsis:
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Affiliation(s)
- Yutaka Sonoda
- Division of Biological Sciences, Graduate School of Science, Hokkaido University, Kita-ku N10-W8, Sapporo, 060-0810 Japan
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Suenaga A, Moriya K, Sonoda Y, Ikeda A, Von Wirén N, Hayakawa T, Yamaguchi J, Yamaya T. Constitutive expression of a novel-type ammonium transporter OsAMT2 in rice plants. PLANT & CELL PHYSIOLOGY 2003; 44:206-11. [PMID: 12610225 DOI: 10.1093/pcp/pcg017] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
To characterize ammonium transport pathways in rice, two cDNAs with high homology to MEP/AMT2-type ammonium transporters, OsAMT2;1 and OsAMT3;1, were isolated. Expression of OsAMT2;1 in an ammonium-uptake-defective yeast mutant showed that this gene encodes functional ammonium transporters. OsAMT2;1 was constitutively expressed in both roots and shoots irrespective of the supply of inorganic nitrogen to the medium, whereas OsAMT3;1 expression was relatively weak. A database search with the amino acid sequence of OsAMT2;1 showed that there are 10 putative OsAMT genes in rice, i.e. three each for OsAMT1, OsAMT2 and OsAMT3, respectively, and one for OsAMT4.
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Affiliation(s)
- Arata Suenaga
- Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, 981-8555 Japan
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36
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Ludewig U, von Wirén N, Frommer WB. Uniport of NH4+ by the root hair plasma membrane ammonium transporter LeAMT1;1. J Biol Chem 2002; 277:13548-55. [PMID: 11821433 DOI: 10.1074/jbc.m200739200] [Citation(s) in RCA: 167] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The transport of ammonium/ammonia is a key process for the acquisition and metabolism of nitrogen. Ammonium transport is mediated by the AMT/MEP/Rh family of membrane proteins which are found in microorganisms, plants, and animals, including the Rhesus blood group antigens in humans. Although ammonium transporters from all kingdoms have been functionally expressed and partially characterized, the transport mechanism, as well as the identity of the true substrate (NH(4+) or NH(3)) remains unclear. Here we describe the functional expression and characterization of LeAMT1;1, a root hair ammonium transporter from tomato (Lycopersicon esculentum) in Xenopus oocytes. Micromolar concentrations of external ammonium were found to induce concentration- and voltage-dependent inward currents in oocytes injected with LeAMT1;1 cRNA, but not in water-injected control oocytes. The NH(4+)-induced currents were more than 3-fold larger than methylammonium currents and were not subject to inhibition by Na(+) or K(+). The voltage dependence of the affinity of LeAMT1;1 toward its substrate strongly suggests that charged NH(4+), rather than NH(3), is the true transport substrate. Furthermore, ammonium transport was independent of the external proton concentration between pH 5.5 and pH 8.5. LeAMT1;1 is concluded to mediate potential-driven NH(4+) uptake and retrieval depending on root membrane potential and NH(4+) concentration gradient.
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Affiliation(s)
- Uwe Ludewig
- Zentrum für Molekularbiologie der Pflanzen, Pflanzenphysiologie, Universität Tübingen, Auf der Morgenstelle 1, Tübingen, Germany.
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37
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Abstract
Rh molecular biology has made many advances since the first Rh cDNA was cloned in 1990. This review summarizes the current knowledge concerning the molecular basis of Rh antigenicity, D-epitope expression, and the structures of the Rh genes and proteins. Although many recent reviews have appeared regarding these subjects, advances in Rh protein function that have been published within the last 12 months have had a fundamental impact on the future direction of Rh research. In November 2000, an article described the role of Rh proteins in ammonium transport, which has remained undescribed in vertebrates, except for non-specific transport via K+ channels. The recent identification of nonerythroid Rh proteins, their expression in diverse tissues, and notably polarized epithelial and endothelial cells will be of broad functional significance and will greatly increase our understanding of the role of Rh in ammonium transport and the biology of ammonium metabolism as a whole. The advances in Rh molecular genetics have enabled the development of diagnostic tests in the clinic. At present, this is largely confined to the prenatal diagnosis of fetal blood group status in alloimmunized pregnancies, but could be extended to the noninvasive prenatal testing of all D-negative pregnant women and eventually, perhaps, to all patient and donor blood.
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Affiliation(s)
- N D Avent
- Centre for Research in Biomedicine, University of the West of England, Bristol, United Kingdom.
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