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Ricachenevsky FK, Punshon T, Lee S, Oliveira BHN, Trenz TS, Maraschin FDS, Hindt MN, Danku J, Salt DE, Fett JP, Guerinot ML. Elemental Profiling of Rice FOX Lines Leads to Characterization of a New Zn Plasma Membrane Transporter, OsZIP7. Front Plant Sci 2018; 9:865. [PMID: 30018622 PMCID: PMC6037872 DOI: 10.3389/fpls.2018.00865] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2018] [Accepted: 06/04/2018] [Indexed: 05/07/2023]
Abstract
Iron (Fe) and zinc (Zn) are essential micronutrients required for proper development in both humans and plants. Rice (Oryza sativa L.) grains are the staple food for nearly half of the world's population, but a poor source of metals such as Fe and Zn. Populations that rely on milled cereals are especially prone to Fe and Zn deficiencies, the most prevalent nutritional deficiencies in humans. Biofortification is a cost-effective solution for improvement of the nutritional quality of crops. However, a better understanding of the mechanisms underlying grain accumulation of mineral nutrients is required before this approach can achieve its full potential. Characterization of gene function is more time-consuming in crops than in model species such as Arabidopsis thaliana. Aiming to more quickly characterize rice genes related to metal homeostasis, we applied the concept of high throughput elemental profiling (ionomics) to Arabidopsis lines heterologously expressing rice cDNAs driven by the 35S promoter, named FOX (Full Length Over-eXpressor) lines. We screened lines expressing candidate genes that could be used in the development of biofortified grain. Among the most promising candidates, we identified two lines ovexpressing the metal cation transporter OsZIP7. OsZIP7 expression in Arabidopsis resulted in a 25% increase in shoot Zn concentrations compared to non-transformed plants. We further characterized OsZIP7 and showed that it is localized to the plasma membrane and is able to complement Zn transport defective (but not Fe defective) yeast mutants. Interestingly, we showed that OsZIP7 does not transport Cd, which is commonly transported by ZIP proteins. Importantly, OsZIP7-expressing lines have increased Zn concentrations in their seeds. Our results indicate that OsZIP7 is a good candidate for developing Zn biofortified rice. Moreover, we showed the use of heterologous expression of genes from crops in A. thaliana as a fast method for characterization of crop genes related to the ionome and potentially useful in biofortification strategies.
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Affiliation(s)
- Felipe K. Ricachenevsky
- Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Departamento de Biologia, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, Santa Maria, Brazil
- Department of Biological Sciences, Dartmouth College, Hanover, NH, United States
- *Correspondence: Felipe K. Ricachenevsky,
| | - Tracy Punshon
- Department of Biological Sciences, Dartmouth College, Hanover, NH, United States
| | - Sichul Lee
- Center for Plant Aging Research, Institute for Basic Science (IBS), Daegu, South Korea
| | - Ben Hur N. Oliveira
- Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Thomaz S. Trenz
- Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | | | - Maria N. Hindt
- Department of Biological Sciences, Dartmouth College, Hanover, NH, United States
| | - John Danku
- School of Biosciences, University of Nottingham, Loughborough, United Kingdom
| | - David E. Salt
- School of Biosciences, University of Nottingham, Loughborough, United Kingdom
| | - Janette P. Fett
- Programa de Pós-Graduação em Biologia Celular e Molecular, Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
- Departamento de Botânica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil
| | - Mary Lou Guerinot
- Department of Biological Sciences, Dartmouth College, Hanover, NH, United States
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Hindt MN, Akmakjian GZ, Pivarski KL, Punshon T, Baxter I, Salt DE, Guerinot ML. BRUTUS and its paralogs, BTS LIKE1 and BTS LIKE2, encode important negative regulators of the iron deficiency response in Arabidopsis thaliana. Metallomics 2017; 9:876-890. [PMID: 28620661 PMCID: PMC5558852 DOI: 10.1039/c7mt00152e] [Citation(s) in RCA: 104] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Iron (Fe) is required for plant health, but it can also be toxic when present in excess. Therefore, Fe levels must be tightly controlled. The Arabidopsis thaliana E3 ligase BRUTUS (BTS) is involved in the negative regulation of the Fe deficiency response and we show here that the two A. thaliana BTS paralogs, BTS LIKE1 (BTSL1) and BTS LIKE2 (BTSL2) encode proteins that act redundantly as negative regulators of the Fe deficiency response. Loss of both of these E3 ligases enhances tolerance to Fe deficiency. We further generated a triple mutant with loss of both BTS paralogs and a partial loss of BTS expression that exhibits even greater tolerance to Fe-deficient conditions and increased Fe accumulation without any resulting Fe toxicity effects. Finally, we identified a mutant carrying a novel missense mutation of BTS that exhibits an Fe deficiency response in the root when grown under both Fe-deficient and Fe-sufficient conditions, leading to Fe toxicity when plants are grown under Fe-sufficient conditions.
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Affiliation(s)
- Maria N Hindt
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755, USA.
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Palmer CM, Hindt MN, Schmidt H, Clemens S, Guerinot ML. MYB10 and MYB72 are required for growth under iron-limiting conditions. PLoS Genet 2013; 9:e1003953. [PMID: 24278034 PMCID: PMC3836873 DOI: 10.1371/journal.pgen.1003953] [Citation(s) in RCA: 146] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 09/27/2013] [Indexed: 12/21/2022] Open
Abstract
Iron is essential for photosynthesis and is often a limiting nutrient for plant productivity. Plants respond to conditions of iron deficiency by increasing transcript abundance of key genes involved in iron homeostasis, but only a few regulators of these genes have been identified. Using genome-wide expression analysis, we searched for transcription factors that are induced within 24 hours after transferring plants to iron-deficient growth conditions. Out of nearly 100 transcription factors shown to be up-regulated, we identified MYB10 and MYB72 as the most highly induced transcription factors. Here, we show that MYB10 and MYB72 are functionally redundant and are required for plant survival in alkaline soil where iron availability is greatly restricted. myb10myb72 double mutants fail to induce transcript accumulation of the nicotianamine synthase gene NAS4. Both myb10myb72 mutants and nas4-1 mutants have reduced iron concentrations, chlorophyll levels, and shoot mass under iron-limiting conditions, indicating that these genes are essential for proper plant growth. The double myb10myb72 mutant also showed nickel and zinc sensitivity, similar to the nas4 mutant. Ectopic expression of NAS4 rescues myb10myb72 plants, suggesting that loss of NAS4 is the primary defect in these plants and emphasizes the importance of nicotianamine, an iron chelator, in iron homeostasis. Overall, our results provide evidence that MYB10 and MYB72 act early in the iron-deficiency regulatory cascade to drive gene expression of NAS4 and are essential for plant survival under iron deficiency.
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Affiliation(s)
- Christine M. Palmer
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, United States of America
| | - Maria N. Hindt
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, United States of America
| | - Holger Schmidt
- Department of Plant Physiology, University of Bayreuth, Bayreuth, Germany
| | - Stephan Clemens
- Department of Plant Physiology, University of Bayreuth, Bayreuth, Germany
| | - Mary Lou Guerinot
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, United States of America
- * E-mail:
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Hindt MN, Guerinot ML. Getting a sense for signals: regulation of the plant iron deficiency response. Biochim Biophys Acta 2012; 1823:1521-30. [PMID: 22483849 PMCID: PMC4008143 DOI: 10.1016/j.bbamcr.2012.03.010] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/19/2012] [Accepted: 03/20/2012] [Indexed: 11/30/2022]
Abstract
Understanding the Fe deficiency response in plants is necessary for improving both plant health and the human diet, which relies on Fe from plant sources. In this review we focus on the regulation of the two major strategies for iron acquisition in plants, exemplified by the model plants Arabidopsis and rice. Critical to our knowledge of Fe homeostasis in plants is determining how Fe is sensed and how this signal is transmitted and integrated into a response. We will explore the evidence for an Fe sensor in plants and summarize the recent findings on hormones and signaling molecules which contribute to the Fe deficiency response. This article is part of a Special Issue entitled: Cell Biology of Metals.
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Affiliation(s)
- Maria N. Hindt
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
| | - Mary Lou Guerinot
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA
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