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Bosch G, Fuentes M, Erro J, Zamarreño ÁM, García-Mina JM. Hydrolysis of riboflavins in root exudates under iron deficiency and alkaline stress. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2024; 210:108573. [PMID: 38569423 DOI: 10.1016/j.plaphy.2024.108573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2023] [Revised: 03/06/2024] [Accepted: 03/26/2024] [Indexed: 04/05/2024]
Abstract
Riboflavins are secreted under iron deficiency as a part of the iron acquisition Strategy I, mainly when the external pH is acidic. In plants growing under Fe-deficiency and alkaline conditions, riboflavins have been reported to accumulate inside the roots, with very low or negligible secretion. However, the fact that riboflavins may undergo hydrolysis under alkaline conditions has been so far disregarded. In this paper, we report the presence of riboflavin derivatives and products of their alkaline hydrolysis (lumichrome, lumiflavin and carboxymethylflavin) in nutrient solutions of Cucumis sativus plants grown under different iron regimes (soluble Fe-EDDHA in the nutrient solution, total absence of iron in the nutrient solution, or two different doses of FeSO4 supplied as a foliar spray), either cultivated in slightly acidic (pH 6) or alkaline (pH 8.8, 10 mM bicarbonate) nutrient solutions. The results show that root synthesis and exudation of riboflavins is controlled by shoot iron status, and that exuded riboflavins undergo hydrolysis, especially at alkaline pH, with lumichrome being the main product of hydrolysis.
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Affiliation(s)
- Germán Bosch
- Universidad de Navarra, Instituto de Biodiversidad y Medioambiente BIOMA, Irunlarrea 1, 31008, Pamplona, Spain; Universidad de Navarra, Facultad de Ciencias, Departamento de Biología Ambiental, Grupo Química y Biología Agrícola, Irunlarrea 1, 31008, Pamplona, Spain.
| | - Marta Fuentes
- Universidad de Navarra, Instituto de Biodiversidad y Medioambiente BIOMA, Irunlarrea 1, 31008, Pamplona, Spain; Universidad de Navarra, Facultad de Ciencias, Departamento de Biología Ambiental, Grupo Química y Biología Agrícola, Irunlarrea 1, 31008, Pamplona, Spain.
| | - Javier Erro
- Universidad de Navarra, Instituto de Biodiversidad y Medioambiente BIOMA, Irunlarrea 1, 31008, Pamplona, Spain; Universidad de Navarra, Facultad de Ciencias, Departamento de Biología Ambiental, Grupo Química y Biología Agrícola, Irunlarrea 1, 31008, Pamplona, Spain.
| | - Ángel M Zamarreño
- Universidad de Navarra, Instituto de Biodiversidad y Medioambiente BIOMA, Irunlarrea 1, 31008, Pamplona, Spain; Universidad de Navarra, Facultad de Ciencias, Departamento de Biología Ambiental, Grupo Química y Biología Agrícola, Irunlarrea 1, 31008, Pamplona, Spain.
| | - José M García-Mina
- Universidad de Navarra, Instituto de Biodiversidad y Medioambiente BIOMA, Irunlarrea 1, 31008, Pamplona, Spain; Universidad de Navarra, Facultad de Ciencias, Departamento de Biología Ambiental, Grupo Química y Biología Agrícola, Irunlarrea 1, 31008, Pamplona, Spain.
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Arcas A, López-Rayo S, Gárate A, Lucena JJ. A Critical Review of Methodologies for Evaluating Iron Fertilizers Based on Iron Reduction and Uptake by Strategy I Plants. PLANTS (BASEL, SWITZERLAND) 2024; 13:819. [PMID: 38592963 PMCID: PMC10975526 DOI: 10.3390/plants13060819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Revised: 02/29/2024] [Accepted: 03/04/2024] [Indexed: 04/11/2024]
Abstract
Under iron (Fe)-limited conditions, plants have developed strategies for acquiring this essential micronutrient. Several Fe sources have been studied as potential fertilizers, with Fe synthetic chelates being the most used to prevent and correct Fe chlorosis in crops. The determination of the activity of the Fe chelate reductase (FCR) enzyme has long been described in the literature to understand the efficiency of Strategy I plants in acquiring Fe from fertilizers under deficient conditions. Other experiments have focused on the translocation of Fe to the plant to define the effectiveness of Fe fertilizers. Yet, both assays are relevant in knowing the capacity of a novel Fe source and other compounds alleviating Fe chlorosis in Strategy I plants. This work reviews the methodologies that are used in FCR assays to evaluate novel Fe fertilizers, including the factors modulating the results obtained for FCR assay activity, such as the Fe substrate, the Fe level during the growing period and during the FCR assay, the pH, the choice of an in vivo or in vitro method, and the plant species. A discussion of the benefits of the concurrence of FCR and Fe uptake assays is then presented alongside a proposed methodology for assessing the effectiveness of Fe fertilizers, emphasizing the importance of understanding chemical and physiological plant interactions. This methodology unifies key factors that modify FCR activity and combines these with the use of the 57Fe tracer to enhance our comprehension of the efficacy of Fe-based fertilizers' effectiveness in alleviating Fe chlorosis. This comprehensive approach not only contributes to the fundamental understanding of Fe-deficient Strategy I plants but also establishes a robust method for determining the efficiency of novel sources for correcting Fe deficiency in plants.
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Affiliation(s)
| | | | | | - Juan J. Lucena
- Department of Agricultural Chemistry and Food Science, Universidad Autónoma de Madrid, 28049 Madrid, Spain; (A.A.); (S.L.-R.); (A.G.)
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Singh P, Chauhan PK, Upadhyay SK, Singh RK, Dwivedi P, Wang J, Jain D, Jiang M. Mechanistic Insights and Potential Use of Siderophores Producing Microbes in Rhizosphere for Mitigation of Stress in Plants Grown in Degraded Land. Front Microbiol 2022; 13:898979. [PMID: 35898908 PMCID: PMC9309559 DOI: 10.3389/fmicb.2022.898979] [Citation(s) in RCA: 36] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Accepted: 06/09/2022] [Indexed: 12/20/2022] Open
Abstract
Plant growth performance under a stressful environment, notably in the agriculture field, is directly correlated with the rapid growth of the human population, which triggers the pressure on crop productivity. Plants perceived many stresses owing to degraded land, which induces low plant productivity and, therefore, becomes a foremost concern for the future to face a situation of food scarcity. Land degradation is a very notable environmental issue at the local, regional, and global levels for agriculture. Land degradation generates global problems such as drought desertification, heavy metal contamination, and soil salinity, which pose challenges to achieving many UN Sustainable Development goals. The plant itself has a varied algorithm for the mitigation of stresses arising due to degraded land; the rhizospheric system of the plant has diverse modes and efficient mechanisms to cope with stress by numerous root-associated microbes. The suitable root-associated microbes and components of root exudate interplay against stress and build adaptation against stress-mediated mechanisms. The problem of iron-deficient soil is rising owing to increasing degraded land across the globe, which hampers plant growth productivity. Therefore, in the context to tackle these issues, the present review aims to identify plant-stress status owing to iron-deficient soil and its probable eco-friendly solution. Siderophores are well-recognized iron-chelating agents produced by numerous microbes and are associated with the rhizosphere. These siderophore-producing microbes are eco-friendly and sustainable agents, which may be managing plant stresses in the degraded land. The review also focuses on the molecular mechanisms of siderophores and their chemistry, cross-talk between plant root and siderophores-producing microbes to combat plant stress, and the utilization of siderophores in plant growth on degraded land.
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Affiliation(s)
- Pratiksha Singh
- Guangxi Key Laboratory for Polysaccharide Materials and Modifications, School of Marine Sciences and Biotechnology, Guangxi Minzu University, Nanning, China
| | - Prabhat K. Chauhan
- Department of Environmental Science, Veer Bahadur Singh Purvanchal University, Jaunpur, India
| | - Sudhir K. Upadhyay
- Department of Environmental Science, Veer Bahadur Singh Purvanchal University, Jaunpur, India
- Sudhir K. Upadhyay
| | - Rajesh Kumar Singh
- Guangxi Key Laboratory of Sugarcane Genetic Improvement, Sugarcane Research Institute, Guangxi Academy of Agricultural Sciences, Nanning, China
| | - Padmanabh Dwivedi
- Department of Plant Physiology, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, India
| | - Jing Wang
- Guangxi Key Laboratory for Polysaccharide Materials and Modifications, School of Marine Sciences and Biotechnology, Guangxi Minzu University, Nanning, China
| | - Devendra Jain
- Department of Molecular Biology and Biotechnology, Maharana Pratap University of Agriculture and Technology, Udaipur, India
| | - Mingguo Jiang
- Guangxi Key Laboratory for Polysaccharide Materials and Modifications, School of Marine Sciences and Biotechnology, Guangxi Minzu University, Nanning, China
- *Correspondence: Mingguo Jiang
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Santos CS, Rodrigues E, Ferreira S, Moniz T, Leite A, Carvalho SMP, Vasconcelos MW, Rangel M. Foliar application of 3-hydroxy-4-pyridinone Fe-chelate [Fe(mpp) 3 ] induces responses at the root level amending iron deficiency chlorosis in soybean. PHYSIOLOGIA PLANTARUM 2021; 173:235-245. [PMID: 33629743 DOI: 10.1111/ppl.13367] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 02/07/2021] [Accepted: 02/10/2021] [Indexed: 06/12/2023]
Abstract
Iron (Fe) deficiency chlorosis (IDC) affects the growth of several crops, especially when growing in alkaline soils. The application of synthetic Fe-chelates is one of the most commonly used strategies in IDC amendment, despite their associated negative environmental impacts. In a previous work, the Fe-chelate tris(3-hydroxy-1-(H)-2-methyl-4-pyridinonate) iron(III) [Fe(mpp)3 ] has shown great potential for alleviating IDC in soybean (Glycine max) in the early stages of plant development under hydroponic conditions. Herein, its efficacy was verified under soil conditions in soybean grown from seed to full maturity. Chlorophyll levels, plant growth, root and shoot mineral accumulation (K, Mg, Ca, Na, P, Mn, Zn, Ni, and Co) and FERRITIN expression were accessed at V5 phenological stage. Compared to a commonly used Fe chelate, FeEDDHA, supplementation with [Fe(mpp)3 ] led to a 29% higher relative chlorophyll content, 32% higher root biomass, 36% higher trifoliate Fe concentration, and a twofold increase in leaf FERRITIN gene expression. [Fe(mpp)3 ] supplementation also resulted in increased accumulation of P, K, Zn, and Co. At full maturity, the remaining plants were harvested and [Fe(mpp)3 ] application led to a 32% seed yield increase when compared to FeEDDHA. This is the first report on the use of [Fe(mpp)3 ] under alkaline soil conditions for IDC correction, and we show that its foliar application has a longer-lasting effect than FeEDDHA, induces efficient root responses, and promotes the uptake of other nutrients.
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Affiliation(s)
- Carla S Santos
- CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal
| | - Elsa Rodrigues
- CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal
- GreenUPorto - Research Centre on Sustainable Agrifood Production and DGAOT, Faculty of Sciences, University of Porto, Vila do Conde, Portugal
| | - Sofia Ferreira
- REQUIMTE, LAQV, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Porto, Portugal
| | - Tânia Moniz
- REQUIMTE, LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Porto, Portugal
| | - Andreia Leite
- REQUIMTE, LAQV, Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade do Porto, Porto, Portugal
| | - Susana M P Carvalho
- GreenUPorto - Research Centre on Sustainable Agrifood Production and DGAOT, Faculty of Sciences, University of Porto, Vila do Conde, Portugal
| | - Marta W Vasconcelos
- CBQF - Centro de Biotecnologia e Química Fina - Laboratório Associado, Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal
| | - Maria Rangel
- REQUIMTE, LAQV, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Porto, Portugal
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Spray treatment of leaves with Fe2+ promotes procyanidin biosynthesis by upregulating the expression of the F3H and ANS genes in red rice grains (Oryza sativa L.). J Cereal Sci 2021. [DOI: 10.1016/j.jcs.2021.103231] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Santos CS, Leite A, Vinhas S, Ferreira S, Moniz T, Vasconcelos MW, Rangel M. A combined physiological and biophysical approach to understand the ligand-dependent efficiency of 3-hydroxy-4-pyridinone Fe-chelates. PLANT DIRECT 2020; 4:e00256. [PMID: 32821874 PMCID: PMC7429444 DOI: 10.1002/pld3.256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 07/20/2020] [Accepted: 07/22/2020] [Indexed: 05/11/2023]
Abstract
Ligands of the 3-hydroxy-4-pyridinone (3,4-HPO) class were considered eligible to formulate new Fe fertilizers for Iron Deficiency Chlorosis (IDC). Soybean (Glycine max L.) plants grown in hydroponic conditions and supplemented with Fe-chelate [Fe(mpp)3] were significantly greener, had increased biomass, and were able to translocate more iron from the roots to the shoots than those supplemented with an equal amount of the commercially available chelate [FeEDDHA]. To understand the influence of the structure of 3,4-HPO ligand on the role of the Fe-chelate to improve Fe-uptake, we investigated and report here the effect of Fe-chelates ([Fe(mpp)3], [Fe(dmpp)3], and [Fe(etpp)3]) in addressing IDC. Chlorosis development was assessed by measurement of morphological parameters, quantification of chlorophyll and Fe, and other micronutrient contents, as well as measurement of enzymatic activity (FCR) and gene expression (FRO2, IRT1, and Ferritin). All [Fe(3,4-HPO)3] chelates were able to provide Fe to plants and prevent IDC but with a different efficiency depending on the ligand. We hypothesize that this may be related with the distinct physicochemical characteristics of ligands and complexes, namely, the diverse hydrophilic-lipophilic balance of the three chelates. To test the hypothesis, we performed an EPR biophysical study using liposomes prepared from a soybean (Glycine3 max L.) lipid extract and spin probes. The results showed that the most effective chelate [Fe(mpp)3] shows a preferential location close to the surface while the others prefer the hydrophobic region inside the bilayer. SIGNIFICANCE STATEMENT The 3-hydroxy-4-pyridinone Fe-chelates, [Fe(mpp)3], [Fe(dmpp)3], and [Fe(etpp)3], were all able to provide Fe to plants and prevent IDC. Efficacy is dependent on the structure of the ligand. From an EPR biophysical study using spin probes and liposomes, prepared from a soybean lipid extract, we hypothesize that this may be related with the distinct preferential location close to the surface or on the hydrophobic region of the lipid bilayer. [Fe(mpp)3] provide higher amounts of Fe in the leaves.
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Affiliation(s)
- Carla S. Santos
- CBQF – Centro de Biotecnologia e Química Fina – Laboratório AssociadoUniversidade Católica PortuguesaEscola Superior de BiotecnologiaPortoPortugal
| | - Andreia Leite
- REQUIMTELAQVDepartamento de Química e BioquímicaFaculdade de CiênciasUniversidade do PortoPortoPortugal
| | - Sílvia Vinhas
- REQUIMTELAQVDepartamento de Química e BioquímicaFaculdade de CiênciasUniversidade do PortoPortoPortugal
| | - Sofia Ferreira
- REQUIMTELAQVInstituto de Ciências Biomédicas de Abel SalazarUniversidade do PortoPortoPortugal
| | - Tânia Moniz
- REQUIMTELAQVDepartamento de Química e BioquímicaFaculdade de CiênciasUniversidade do PortoPortoPortugal
| | - Marta W. Vasconcelos
- CBQF – Centro de Biotecnologia e Química Fina – Laboratório AssociadoUniversidade Católica PortuguesaEscola Superior de BiotecnologiaPortoPortugal
| | - Maria Rangel
- REQUIMTELAQVInstituto de Ciências Biomédicas de Abel SalazarUniversidade do PortoPortoPortugal
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Islas-Valdez S, López-Rayo S, Arcos J, Menéndez N, Lucena JJ. Effect of Fe:ligand ratios on hydroponic conditions and calcareous soil in Solanum lycopersicum L. and Glycine max L. fertilized with heptagluconate and gluconate. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2020; 100:1106-1117. [PMID: 31667842 DOI: 10.1002/jsfa.10119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Revised: 10/16/2019] [Accepted: 10/31/2019] [Indexed: 06/10/2023]
Abstract
BACKGROUND The environmental risk from the application of synthetic chelates has led to the use of biodegradable complexes to correct Fe deficiency in plants. In this article, the Fe oxidation state, the Fe:ligand ratio, and the molecular weight distribution for heptagluconate (G7) and gluconate (G6) are considered as key factors for the efficacy of complexes as fertilizers. Complexes with different Fe:ligand ratios were prepared and analyzed by gel filtration chromatography (GFC). The ability of Fe:ligand ratios to provide Fe to tomato in hydroponics and soybean in calcareous soil was tested and compared with synthetic chelates (Fe3+ :HBED and Fe3+ :EDTA). RESULTS G7 presented greater capacity to complex both Fe(II) and Fe(III) than G6, but the Fe(II) complexes exhibited poor stability at pH 9 and oxidation in solution. Gel filtration chromatography demonstrated the polynuclear nature of the Fe3+ :G7 at various ratios. The effectiveness of the Fe fertilizers depend on the Fe3+ :ligand ratio and the ligand type, the Fe3+ :G7 (1:1 and 1:2) being the most effective. Fe3+ :G7 (1:1) also presented a better response for the uptake of other micronutrients. CONCLUSION Fe3+ :G7 molar ratios have been shown to be critical for plant Fe uptake under hydroponic conditions and with calcareous soil. Thus, the Fe3+ :G7 at equimolar ratio and 1:2 molar ratio can be an environmentally friendly alternative to less degradable synthetic chelates to correct Fe chlorosis in strategy I plants. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Samira Islas-Valdez
- Department of Agricultural Chemistry and Food Science, Universidad Autónoma de Madrid, Madrid, Spain
| | - Sandra López-Rayo
- Department of Agricultural Chemistry and Food Science, Universidad Autónoma de Madrid, Madrid, Spain
| | - Jessica Arcos
- Department of Agricultural Chemistry and Food Science, Universidad Autónoma de Madrid, Madrid, Spain
| | - Nieves Menéndez
- Department of Applied Physical-Chemistry, Universidad Autónoma de Madrid, Madrid, Spain
| | - Juan J Lucena
- Department of Agricultural Chemistry and Food Science, Universidad Autónoma de Madrid, Madrid, Spain
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Cieschi MT, Polyakov AY, Lebedev VA, Volkov DS, Pankratov DA, Veligzhanin AA, Perminova IV, Lucena JJ. Eco-Friendly Iron-Humic Nanofertilizers Synthesis for the Prevention of Iron Chlorosis in Soybean ( Glycine max) Grown in Calcareous Soil. FRONTIERS IN PLANT SCIENCE 2019; 10:413. [PMID: 31024589 PMCID: PMC6460895 DOI: 10.3389/fpls.2019.00413] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 03/19/2019] [Indexed: 05/08/2023]
Abstract
Iron deficiency is a frequent problem for many crops, particularly in calcareous soils and iron humates are commonly applied in the Mediterranean basin in spite of their lesser efficiency than iron synthetic chelates. Development and application of new fertilizers using nanotechnology are one of the potentially effective options of enhancing the iron humates, according to the sustainable agriculture. Particle size, pH, and kinetics constrain the iron humate efficiency. Thus, it is relevant to understand the iron humate mechanism in the plant-soil system linking their particle size, characterization and iron distribution in plant and soil using 57Fe as a tracer tool. Three hybrid nanomaterials (F, S, and M) were synthesized as iron-humic nanofertilizers (57Fe-NFs) from leonardite potassium humate and 57Fe used in the form of 57Fe(NO3)3 or 57Fe2(SO4)3. They were characterized using Mössbauer spectroscopy, X-ray diffraction (XRD), extended X-ray absorption fine structure spectroscopy (EXAFS), transmission electron microscopy (TEM) and tested for iron availability in a calcareous soil pot experiment carried out under growth chamber conditions. Three doses (35, 75, and 150 μmol pot-1) of each iron-humic material were applied to soybean iron deficient plants and their iron nutrition contributions were compared to 57FeEDDHA and leonardite potassium humate as control treatments. Ferrihydrite was detected as the main structure of all three 57Fe-NFs and the plants tested with iron-humic compounds exhibited continuous long-term statistically reproducible iron uptake and showed high shoot fresh weight. Moreover, the 57Fe from the humic nanofertilizers remained available in soil and was detected in soybean pods. The Fe-NFs offers a natural, low cost and environmental option to the traditional iron fertilization in calcareous soils.
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Affiliation(s)
- María T. Cieschi
- Department of Agricultural Chemistry and Food Science, Autonomous University of Madrid, Madrid, Spain
| | - Alexander Yu Polyakov
- Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Moscow, Russia
- Department of Materials Science, Lomonosov Moscow State University, Moscow, Russia
| | - Vasily A. Lebedev
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia
| | - Dmitry S. Volkov
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia
- Department of Chemistry and Physical Chemistry of Soils, V.V. Dokuchaev Soil Science Institute, Moscow, Russia
| | - Denis A. Pankratov
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia
| | | | - Irina V. Perminova
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russia
- *Correspondence: Irina V. Perminova, Juan J. Lucena,
| | - Juan J. Lucena
- Department of Agricultural Chemistry and Food Science, Autonomous University of Madrid, Madrid, Spain
- *Correspondence: Irina V. Perminova, Juan J. Lucena,
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Abstract
This review deals with two essential plant mineral nutrients, iron (Fe) and phosphorus (P); the acquisition of both has important environmental and economic implications. Both elements are abundant in soils but are scarcely available to plants. To prevent deficiency, dicot plants develop physiological and morphological responses in their roots to specifically acquire Fe or P. Hormones and signalling substances, like ethylene, auxin and nitric oxide (NO), are involved in the activation of nutrient-deficiency responses. The existence of common inducers suggests that they must act in conjunction with nutrient-specific signals in order to develop nutrient-specific deficiency responses. There is evidence suggesting that P- or Fe-related phloem signals could interact with ethylene and NO to confer specificity to the responses to Fe- or P-deficiency, avoiding their induction when ethylene and NO increase due to other nutrient deficiency or stress. The mechanisms responsible for such interaction are not clearly determined, and thus, the regulatory networks that allow or prevent cross talk between P and Fe deficiency responses remain obscure. Here, fragmented information is drawn together to provide a clearer overview of the mechanisms and molecular players involved in the regulation of the responses to Fe or P deficiency and their interactions.
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