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Kolbert Z, Barroso JB, Boscari A, Corpas FJ, Gupta KJ, Hancock JT, Lindermayr C, Palma JM, Petřivalský M, Wendehenne D, Loake GJ. Interorgan, intraorgan and interplant communication mediated by nitric oxide and related species. THE NEW PHYTOLOGIST 2024. [PMID: 39223868 DOI: 10.1111/nph.20085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2024] [Accepted: 07/29/2024] [Indexed: 09/04/2024]
Abstract
Plant survival to a potential plethora of diverse environmental insults is underpinned by coordinated communication amongst organs to help shape effective responses to these environmental challenges at the whole plant level. This interorgan communication is supported by a complex signal network that regulates growth, development and environmental responses. Nitric oxide (NO) has emerged as a key signalling molecule in plants. However, its potential role in interorgan communication has only recently started to come into view. Direct and indirect evidence has emerged supporting that NO and related species (S-nitrosoglutathione, nitro-linolenic acid) are mobile interorgan signals transmitting responses to stresses such as hypoxia and heat. Beyond their role as mobile signals, NO and related species are involved in mediating xylem development, thus contributing to efficient root-shoot communication. Moreover, NO and related species are regulators in intraorgan systemic defence responses aiming an effective, coordinated defence against pathogens. Beyond its in planta signalling role, NO and related species may act as ex planta signals coordinating external leaf-to-leaf, root-to-leaf but also plant-to-plant communication. Here, we discuss these exciting developments and emphasise how their manipulation may provide novel strategies for crop improvement.
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Affiliation(s)
- Zsuzsanna Kolbert
- Department of Plant Biology, University of Szeged, H6726, Szeged, Hungary
| | - Juan B Barroso
- Group of Biochemistry and Cell Signalling in Nitric Oxide, University of Jaén, Campus Universitario 'Las Lagunillas' s/n, E-23071, Jaén, Spain
| | - Alexandre Boscari
- Institut Sophia Agrobiotech, UMR INRAE 1355, Université Côte d'Azur, CNRS 7254, 400 route des Chappes, BP 167, 06903, Sophia Antipolis, France
| | - Francisco J Corpas
- Group of Antioxidants, Free Radicals and Nitric Oxide in Biotechnology, Food and Agriculture, Department of Stress, Development and Signaling in Plants, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Profesor Albareda 1, 18008, Granada, Spain
| | | | - John T Hancock
- Department of Applied Sciences, University of the West of England, Bristol, BS16 1QY, UK
| | - Christian Lindermayr
- Institute of Lung Health and Immunity, Helmholtz Zentrum München - German Research Center for Environmental Health, 85764, Munich/Neuherberg, Germany
| | - José Manuel Palma
- Group of Antioxidants, Free Radicals and Nitric Oxide in Biotechnology, Food and Agriculture, Department of Stress, Development and Signaling in Plants, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Profesor Albareda 1, 18008, Granada, Spain
| | - Marek Petřivalský
- Department of Biochemistry, Faculty of Science, Palacký University, Šlechtitelů 27, CZ-783 71, Olomouc, Czech Republic
| | - David Wendehenne
- Agroécologie, INRAE, Institut Agro Dijon, Univiversité de Bourgogne, 21000, Dijon, France
| | - Gary J Loake
- Institute of Molecular Plant Sciences, University of Edinburgh, Edinburgh, EH9 3BF, UK
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2
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Minguillón S, Fischer-Schrader K, Pérez-Rontomé C, Matamoros MA, Becana M. The enigmatic enzyme 'amidoxime reducing component' of Lotus japonicus. Characterization, expression, activity in plant tissues, and proposed role as a nitric oxide-forming nitrite reductase. PHYSIOLOGIA PLANTARUM 2024; 176:e14438. [PMID: 39054574 DOI: 10.1111/ppl.14438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Revised: 06/05/2024] [Accepted: 06/13/2024] [Indexed: 07/27/2024]
Abstract
Human mitochondria contain a molybdoprotein capable of reducing amidoximes using cytochrome b5/cytochrome b5 reductase (Cb/CbR). This 'amidoxime reducing component' (ARC) also reduces nitrite to nitric oxide (NO). In the plant kingdom, distinct functions have been suggested for ARCs. Thus, the single ARC of Chlamydomonas reinhardtii (crARC) reduces nitrite to NO by taking electrons from nitrate reductase (NR). Therefore, it was proposed that a dual NR/crARC system can generate NO under physiological conditions and the crARC was renamed to 'NO-forming nitrite reductase' (NOFNiR). In contrast to this, the two ARC enzymes from Arabidopsis thaliana were not found to produce NO in vitro at physiological nitrite concentrations, suggesting a different, as yet unknown, function in vascular plants. Here, we have investigated the two ARCs of Lotus japonicus (LjARCs) to shed light on this controversy and to examine, for the first time, the distribution of ARCs in plant tissues. The LjARCs are localized in the cytosol and their activities and catalytic efficiencies, which are much higher than those of A. thaliana, are consistent with a role as NOFNiR. LjARCs are prone to S-nitrosylation in vitro by S-nitrosoglutathione and this post-translational modification drastically inhibits their activities. The enzymes are mainly expressed in flowers, seeds and pods, but are absent in nodules. LjARCs are active with NR and Cb/CbR as electron-transferring systems. However, the LjNR mRNA levels in seeds and pods are negligible, whereas our proteomic analyses show that pods contain the two ARCs, Cb and CbR. We conclude that LjARCs may play a role as NOFNiR by receiving electrons from the Cb/CbR system but do not act in combination with NR.
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Affiliation(s)
- Samuel Minguillón
- Departamento de Biología Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Zaragoza, Spain
| | - Katrin Fischer-Schrader
- Institute of Biochemistry, Department of Chemistry and Biochemistry, University of Cologne, Germany
| | - Carmen Pérez-Rontomé
- Departamento de Biología Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Zaragoza, Spain
| | - Manuel A Matamoros
- Departamento de Biología Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Zaragoza, Spain
| | - Manuel Becana
- Departamento de Biología Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas (CSIC), Zaragoza, Spain
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3
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Weber JN, Minner-Meinen R, Kaufholdt D. The Mechanisms of Molybdate Distribution and Homeostasis with Special Focus on the Model Plant Arabidopsis thaliana. Molecules 2023; 29:40. [PMID: 38202623 PMCID: PMC10780190 DOI: 10.3390/molecules29010040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Revised: 12/08/2023] [Accepted: 12/15/2023] [Indexed: 01/12/2024] Open
Abstract
This review article deals with the pathways of cellular and global molybdate distribution in plants, especially with a full overview for the model plant Arabidopsis thaliana. In its oxidized state as bioavailable molybdate, molybdenum can be absorbed from the environment. Especially in higher plants, molybdenum is indispensable as part of the molybdenum cofactor (Moco), which is responsible for functionality as a prosthetic group in a variety of essential enzymes like nitrate reductase and sulfite oxidase. Therefore, plants need mechanisms for molybdate import and transport within the organism, which are accomplished via high-affinity molybdate transporter (MOT) localized in different cells and membranes. Two different MOT families were identified. Legumes like Glycine max or Medicago truncatula have an especially increased number of MOT1 family members for supplying their symbionts with molybdate for nitrogenase activity. In Arabidopsis thaliana especially, the complete pathway followed by molybdate through the plant is traceable. Not only the uptake from soil by MOT1.1 and its distribution to leaves, flowers, and seeds by MOT2-family members was identified, but also that inside the cell. the transport trough the cytoplasm and the vacuolar storage mechanisms depending on glutathione were described. Finally, supplying the Moco biosynthesis complex by MOT1.2 and MOT2.1 was demonstrated.
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Affiliation(s)
| | | | - David Kaufholdt
- Institut für Pflanzenbiologie, Technische Universität Braunschweig, Humboldtstrasse 1, D-38106 Braunschweig, Germany
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Struwe MA, Scheidig AJ, Clement B. The mitochondrial amidoxime reducing component-from prodrug-activation mechanism to drug-metabolizing enzyme and onward to drug target. J Biol Chem 2023; 299:105306. [PMID: 37778733 PMCID: PMC10637980 DOI: 10.1016/j.jbc.2023.105306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 09/17/2023] [Accepted: 09/24/2023] [Indexed: 10/03/2023] Open
Abstract
The mitochondrial amidoxime-reducing component (mARC) is one of five known molybdenum enzymes in eukaryotes. mARC belongs to the MOSC domain superfamily, a large group of so far poorly studied molybdoenzymes. mARC was initially discovered as the enzyme activating N-hydroxylated prodrugs of basic amidines but has since been shown to also reduce a variety of other N-oxygenated compounds, for example, toxic nucleobase analogs. Under certain circumstances, mARC might also be involved in reductive nitric oxide synthesis through reduction of nitrite. Recently, mARC enzymes have received a lot of attention due to their apparent involvement in lipid metabolism and, in particular, because many genome-wide association studies have shown a common variant of human mARC1 to have a protective effect against liver disease. The mechanism linking mARC enzymes with lipid metabolism remains unknown. Here, we give a comprehensive overview of what is currently known about mARC enzymes, their substrates, structure, and apparent involvement in human disease.
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Affiliation(s)
- Michel A Struwe
- Zoologisches Institut - Strukturbiologie, Christian-Albrechts-Universität Kiel, Kiel, Germany; Pharmazeutisches Institut, Christian-Albrechts-Universität Kiel, Kiel, Germany.
| | - Axel J Scheidig
- Zoologisches Institut - Strukturbiologie, Christian-Albrechts-Universität Kiel, Kiel, Germany
| | - Bernd Clement
- Pharmazeutisches Institut, Christian-Albrechts-Universität Kiel, Kiel, Germany
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Aroca A, García-Díaz I, García-Calderón M, Gotor C, Márquez AJ, Betti M. Photorespiration: regulation and new insights on the potential role of persulfidation. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:6023-6039. [PMID: 37486799 PMCID: PMC10575701 DOI: 10.1093/jxb/erad291] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 07/21/2023] [Indexed: 07/26/2023]
Abstract
Photorespiration has been considered a 'futile' cycle in C3 plants, necessary to detoxify and recycle the metabolites generated by the oxygenating activity of Rubisco. However, several reports indicate that this metabolic route plays a fundamental role in plant metabolism and constitutes a very interesting research topic. Many open questions still remain with regard to photorespiration. One of these questions is how the photorespiratory process is regulated in plants and what factors contribute to this regulation. In this review, we summarize recent advances in the regulation of the photorespiratory pathway with a special focus on the transcriptional and post-translational regulation of photorespiration and the interconnections of this process with nitrogen and sulfur metabolism. Recent findings on sulfide signaling and protein persulfidation are also described.
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Affiliation(s)
- Angeles Aroca
- Instituto de Bioquímica Vegetal y Fotosíntesis (Universidad de Sevilla, Consejo Superior de Investigaciones Científicas), Américo Vespucio 49, 41092 Sevilla, Spain
- Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Química, Universidad de Sevilla, C/Profesor García González, 1, 41012 Sevilla, Spain
| | - Inmaculada García-Díaz
- Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Química, Universidad de Sevilla, C/Profesor García González, 1, 41012 Sevilla, Spain
| | - Margarita García-Calderón
- Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Química, Universidad de Sevilla, C/Profesor García González, 1, 41012 Sevilla, Spain
| | - Cecilia Gotor
- Instituto de Bioquímica Vegetal y Fotosíntesis (Universidad de Sevilla, Consejo Superior de Investigaciones Científicas), Américo Vespucio 49, 41092 Sevilla, Spain
| | - Antonio J Márquez
- Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Química, Universidad de Sevilla, C/Profesor García González, 1, 41012 Sevilla, Spain
| | - Marco Betti
- Departamento de Bioquímica Vegetal y Biología Molecular, Facultad de Química, Universidad de Sevilla, C/Profesor García González, 1, 41012 Sevilla, Spain
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6
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Tejada-Jimenez M, Leon-Miranda E, Llamas A. Chlamydomonas reinhardtii-A Reference Microorganism for Eukaryotic Molybdenum Metabolism. Microorganisms 2023; 11:1671. [PMID: 37512844 PMCID: PMC10385300 DOI: 10.3390/microorganisms11071671] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 06/19/2023] [Accepted: 06/23/2023] [Indexed: 07/30/2023] Open
Abstract
Molybdenum (Mo) is vital for the activity of a small but essential group of enzymes called molybdoenzymes. So far, specifically five molybdoenzymes have been discovered in eukaryotes: nitrate reductase, sulfite oxidase, xanthine dehydrogenase, aldehyde oxidase, and mARC. In order to become biologically active, Mo must be chelated to a pterin, forming the so-called Mo cofactor (Moco). Deficiency or mutation in any of the genes involved in Moco biosynthesis results in the simultaneous loss of activity of all molybdoenzymes, fully or partially preventing the normal development of the affected organism. To prevent this, the different mechanisms involved in Mo homeostasis must be finely regulated. Chlamydomonas reinhardtii is a unicellular, photosynthetic, eukaryotic microalga that has produced fundamental advances in key steps of Mo homeostasis over the last 30 years, which have been extrapolated to higher organisms, both plants and animals. These advances include the identification of the first two molybdate transporters in eukaryotes (MOT1 and MOT2), the characterization of key genes in Moco biosynthesis, the identification of the first enzyme that protects and transfers Moco (MCP1), the first characterization of mARC in plants, and the discovery of the crucial role of the nitrate reductase-mARC complex in plant nitric oxide production. This review aims to provide a comprehensive summary of the progress achieved in using C. reinhardtii as a model organism in Mo homeostasis and to propose how this microalga can continue improving with the advancements in this field in the future.
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Affiliation(s)
- Manuel Tejada-Jimenez
- Department of Biochemistry and Molecular Biology, Campus de Rabanales and Campus Internacional de Excelencia Agroalimentario (CeiA3), Edificio Severo Ochoa, University of Córdoba, 14071 Córdoba, Spain
| | - Esperanza Leon-Miranda
- Department of Biochemistry and Molecular Biology, Campus de Rabanales and Campus Internacional de Excelencia Agroalimentario (CeiA3), Edificio Severo Ochoa, University of Córdoba, 14071 Córdoba, Spain
| | - Angel Llamas
- Department of Biochemistry and Molecular Biology, Campus de Rabanales and Campus Internacional de Excelencia Agroalimentario (CeiA3), Edificio Severo Ochoa, University of Córdoba, 14071 Córdoba, Spain
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7
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Caubrière D, Moseler A, Rouhier N, Couturier J. Diversity and roles of cysteine desulfurases in photosynthetic organisms. JOURNAL OF EXPERIMENTAL BOTANY 2023; 74:3345-3360. [PMID: 36861318 DOI: 10.1093/jxb/erad065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 02/22/2023] [Indexed: 06/08/2023]
Abstract
As sulfur is part of many essential protein cofactors such as iron-sulfur clusters, molybdenum cofactors, or lipoic acid, its mobilization from cysteine represents a fundamental process. The abstraction of the sulfur atom from cysteine is catalysed by highly conserved pyridoxal 5'-phosphate-dependent enzymes called cysteine desulfurases. The desulfuration of cysteine leads to the formation of a persulfide group on a conserved catalytic cysteine and the concomitant release of alanine. Sulfur is then transferred from cysteine desulfurases to different targets. Numerous studies have focused on cysteine desulfurases as sulfur-extracting enzymes for iron-sulfur cluster synthesis in mitochondria and chloroplasts but also for molybdenum cofactor sulfuration in the cytosol. Despite this, knowledge about the involvement of cysteine desulfurases in other pathways is quite rudimentary, particularly in photosynthetic organisms. In this review, we summarize current understanding of the different groups of cysteine desulfurases and their characteristics in terms of primary sequence, protein domain architecture, and subcellular localization. In addition, we review the roles of cysteine desulfurases in different fundamental pathways and highlight the gaps in our knowledge to encourage future work on unresolved issues especially in photosynthetic organisms.
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Affiliation(s)
| | - Anna Moseler
- Institute of Crop Science and Resource Conservation (INRES) - Chemical Signalling, University of Bonn, 53113 Bonn, Germany
| | | | - Jérémy Couturier
- Université de Lorraine, INRAE, IAM, F-54000 Nancy, France
- Institut Universitaire de France, F-75000, Paris, France
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Martins TDS, Da-Silva CJ, Shimoia EP, Posso DA, Carvalho IR, de Oliveira ACB, do Amarante L. Nitrate supply decreases fermentation and alleviates oxidative and ionic stress in nitrogen-fixing soybean exposed to saline waterlogging. FUNCTIONAL PLANT BIOLOGY : FPB 2023; 50:416-433. [PMID: 37038091 DOI: 10.1071/fp22145] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 03/18/2023] [Indexed: 05/03/2023]
Abstract
Nitrate (NO3 - ) nutrition is known to mitigate the damages caused by individual stresses of waterlogging and salinity. Here, we investigated the role of NO3 - in soybean plants exposed to these stresses in combination. Nodulated soybean cultivated under greenhouse conditions and daily fertilised with a nutrient solution without nitrogen were subjected to the following treatments: Water, NO3 - , NaCl, and NaCl+NO3 - . Then, plants were exposed to waterlogging (6days) and drainage (2days). Compared to plants exposed to isolated stress, the saline waterlogging resulted in higher concentrations of H2 O2 , O2 ˙- , and lipid peroxidation at the whole-plant level, mainly during drainage. Furthermore, saline waterlogging increased fermentation and the concentrations of Na+ and K+ in roots and leaves both during waterlogging and drainage. NO3 - supplementation led to augments in NO3 - and NO levels, and stimulated nitrate reductase activity in both organs. In addition, NO3 - nutrition alleviated oxidative stress and fermentation besides increasing the K+ /Na+ ratio in plants exposed to saline waterlogging. In conclusion, NO3 - supplementation is a useful strategy to help soybean plants overcome saline waterlogging stress. These findings are of high relevance for agriculture as soybean is an important commodity and has been cultivated in areas prone to saline waterlogging.
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Affiliation(s)
| | | | | | - Douglas Antônio Posso
- Departamento de Botânica, Universidade Federal de Pelotas, Capão do Leão 96160-000, Brazil
| | - Ivan Ricardo Carvalho
- Departamento de Estudos Agrários, Universidade Regional do Noroeste do Estado do Rio Grande do Sul, Ijuí 98700-000, Brazil
| | | | - Luciano do Amarante
- Departamento de Botânica, Universidade Federal de Pelotas, Capão do Leão 96160-000, Brazil
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Minguillón S, Matamoros MA, Duanmu D, Becana M. Signaling by reactive molecules and antioxidants in legume nodules. THE NEW PHYTOLOGIST 2022; 236:815-832. [PMID: 35975700 PMCID: PMC9826421 DOI: 10.1111/nph.18434] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 07/29/2022] [Indexed: 06/15/2023]
Abstract
Legume nodules are symbiotic structures formed as a result of the interaction with rhizobia. Nodules fix atmospheric nitrogen into ammonia that is assimilated by the plant and this process requires strict metabolic regulation and signaling. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are involved as signal molecules at all stages of symbiosis, from rhizobial infection to nodule senescence. Also, reactive sulfur species (RSS) are emerging as important signals for an efficient symbiosis. Homeostasis of reactive molecules is mainly accomplished by antioxidant enzymes and metabolites and is essential to allow redox signaling while preventing oxidative damage. Here, we examine the metabolic pathways of reactive molecules and antioxidants with an emphasis on their functions in signaling and protection of symbiosis. In addition to providing an update of recent findings while paying tribute to original studies, we identify several key questions. These include the need of new methodologies to detect and quantify ROS, RNS, and RSS, avoiding potential artifacts due to their short lifetimes and tissue manipulation; the regulation of redox-active proteins by post-translational modification; the production and exchange of reactive molecules in plastids, peroxisomes, nuclei, and bacteroids; and the unknown but expected crosstalk between ROS, RNS, and RSS in nodules.
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Affiliation(s)
- Samuel Minguillón
- Departamento de BiologíaVegetal, Estación Experimental de Aula DeiConsejo Superior de Investigaciones CientíficasApartado 1303450080ZaragozaSpain
| | - Manuel A. Matamoros
- Departamento de BiologíaVegetal, Estación Experimental de Aula DeiConsejo Superior de Investigaciones CientíficasApartado 1303450080ZaragozaSpain
| | - Deqiang Duanmu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and TechnologyHuazhong Agricultural UniversityWuhan430070China
| | - Manuel Becana
- Departamento de BiologíaVegetal, Estación Experimental de Aula DeiConsejo Superior de Investigaciones CientíficasApartado 1303450080ZaragozaSpain
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10
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Physiological Importance of Molybdate Transporter Family 1 in Feeding the Molybdenum Cofactor Biosynthesis Pathway in Arabidopsis thaliana. Molecules 2022; 27:molecules27103158. [PMID: 35630635 PMCID: PMC9147641 DOI: 10.3390/molecules27103158] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2022] [Revised: 05/09/2022] [Accepted: 05/12/2022] [Indexed: 02/04/2023] Open
Abstract
Molybdate uptake and molybdenum cofactor (Moco) biosynthesis were investigated in detail in the last few decades. The present study critically reviews our present knowledge about eukaryotic molybdate transporters (MOT) and focuses on the model plant Arabidopsis thaliana, complementing it with new experiments, filling missing gaps, and clarifying contradictory results in the literature. Two molybdate transporters, MOT1.1 and MOT1.2, are known in Arabidopsis, but their importance for sufficient molybdate supply to Moco biosynthesis remains unclear. For a better understanding of their physiological functions in molybdate homeostasis, we studied the impact of mot1.1 and mot1.2 knock-out mutants, including a double knock-out on molybdate uptake and Moco-dependent enzyme activity, MOT localisation, and protein–protein interactions. The outcome illustrates different physiological roles for Moco biosynthesis: MOT1.1 is plasma membrane located and its function lies in the efficient absorption of molybdate from soil and its distribution throughout the plant. However, MOT1.1 is not involved in leaf cell imports of molybdate and has no interaction with proteins of the Moco biosynthesis complex. In contrast, the tonoplast-localised transporter MOT1.2 exports molybdate stored in the vacuole and makes it available for re-localisation during senescence. It also supplies the Moco biosynthesis complex with molybdate by direct interaction with molybdenum insertase Cnx1 for controlled and safe sequestering.
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