Effect of Fe-Catalyzed Photooxidation of EDTA on Root Growth in Plant Culture Media

Hangarter, Roger P.; Stasinopoulos, Triant C.

doi:10.1104/pp.96.3.843

Cited by 62 publications

(35 citation statements)

References 12 publications

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“…Plates were incubated at 22°C under constant illumination for 12 to 14 d until they reached the 4-to 6-true-leaf stage. Yellow filters (acrylic yellow-2208, Cadillac Plastic and Chemical, Pittsburgh) were placed between the lights and plants to prevent the photochemical degradation of Fe(III)-EDTA (Hangarter and Stasinopoulos, 1991).…”

Section: Plant Growth Conditionsmentioning

confidence: 99%

Overexpression of the FRO2 Ferric Chelate Reductase Confers Tolerance to Growth on Low Iron and Uncovers Posttranscriptional Control

et al. 2003

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The Arabidopsis FRO2 gene encodes the low-iron-inducible ferric chelate reductase responsible for reduction of iron at the root surface. Here, we report that FRO2 and IRT1, the major transporter responsible for high-affinity iron uptake from the soil, are coordinately regulated at both the transcriptional and posttranscriptional levels. FRO2 and IRT1 are induced together following the imposition of iron starvation and are coordinately repressed following iron resupply. Steady-state mRNA levels of FRO2 and IRT1 are also coordinately regulated by zinc and cadmium. Like IRT1, FRO2 mRNA is detected in the epidermal cells of roots, consistent with its proposed role in iron uptake from the soil. FRO2 mRNA is detected at high levels in the roots and shoots of 35S-FRO2 transgenic plants. However, ferric chelate reductase activity is only elevated in the 35S-FRO2 plants under conditions of iron deficiency, indicating that FRO2 is subject to posttranscriptional regulation, as shown previously for IRT1. Finally, the 35S-FRO2 plants grow better on low iron as compared with wild-type plants, supporting the idea that reduction of ferric iron to ferrous iron is the rate-limiting step in iron uptake.Iron is an essential element for plants. It functions to accept and donate electrons and thus serves as an important cofactor for a number of metalloenzymes involved in respiration and photosynthesis. Although iron is abundant in the earth's crust, it is often unavailable to plants because it tends to form insoluble ferric hydroxide complexes in aerobic environments at neutral or basic pH (Guerinot and Yi, 1994). In addition to the solubility problem, the chemical properties of iron require cells to place limitations on its accumulation. Fe(II) and Fe(III) act catalytically to generate hydroxyl radicals that can damage cellular constituents such as DNA and lipids (Halliwell and Gutteridge, 1992). Thus, iron uptake (Eide et al., 1996;Robinson et al., 1999;Connolly et al., 2002) and storage (Lescure et al., 1991;Briat and Lobréaux, 1997;Wei and Theil, 2000) are carefully regulated processes.Dicots and non-grass monocots employ the strategy I response to mobilize iron from the soil (Marschner and Rö mheld, 1994). This response includes release of protons and subsequent acidification of the rhizosphere, which serves to drive more Fe(III) into solution, reduction of Fe(III) to Fe(II) at the root surface, and transport of Fe(II) across the root epidermal cell membrane. We have previously identified the genes in Arabidopsis that encode the ironregulated ferric chelate reductase (FRO2) and the ferrous iron transporter (IRT1) that function to take up iron from the soil as part of the strategy I response (Eide et al., 1996;Yi and Guerinot, 1996;Robinson et al., 1999;Vert et al., 2002). FRO2 is predicted to encode a polypeptide of 725 amino acids, with conserved FAD-and NADPH-binding sites. FRO2 has six hydrophobic domains within its amino-terminal region along with two additional carboxyl-terminal hydrophobic domains, all of which are predict...

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Section: Plant Growth Conditionsmentioning

confidence: 99%

Overexpression of the FRO2 Ferric Chelate Reductase Confers Tolerance to Growth on Low Iron and Uncovers Posttranscriptional Control

et al. 2003

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“…Plants were grown in a controlled environment plant growth chamber (Percival Scientific) under constant illumination (100 mE m 22 s 21 ) at 22°C for 2 weeks. The seedlings were placed beneath a yellow filter (acrylic yellow-2208; Cadillac Plastic and Chemical) to prevent the photochemical degradation of Fe(III)-EDTA (Hangarter and Stasinopoulos, 1991 (Marschner et al, 1982) and 1 mM MES, 0.6% agar, pH 6.0. Plants were grown for 3 d in a growth chamber as described above.…”

Section: Plant Growth Conditionsmentioning

confidence: 99%

Iron-Induced Turnover of the Arabidopsis IRON-REGULATED TRANSPORTER1 Metal Transporter Requires Lysine Residues

et al. 2008

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Iron is an essential micronutrient but is toxic if accumulated at high levels. Thus, iron uptake and distribution in plants are controlled by precise regulatory mechanisms. IRON-REGULATED TRANSPORTER1 (IRT1) is the major high affinity iron transporter responsible for iron uptake from the soil in Arabidopsis (Arabidopsis thaliana). Previously, we showed that IRT1 is subject to posttranscriptional regulation; when expressed from the constitutive cauliflower mosaic virus 35S promoter, IRT1 protein accumulates only in iron-deficient roots. IRT1 contains an intracellular loop that may be critical for posttranslational regulation by metals. Of particular interest are a histidine (His) motif (HGHGHGH) that might bind metals and two lysine residues that could serve as attachment sites for ubiquitin. We constructed a set of mutant IRT1 alleles: IRT1H154Q, IRT1H156Q, IRT1H158Q, IRT1H160Q, IRT14HQ (quadruple His mutant), IRT1K146R, IRT1K171R, and a double mutant (IRT1K146R,K171R). Mutation of the His or lysine residues did not eliminate the ability of IRT1 to transport iron or zinc. Expression of each of the IRT1 variants and an IRT1intact construct in plants from the 35S promoter revealed that either K146 or K171 is required for iron-induced protein turnover, and 35S-IRT1K146R,K171R plants contain higher levels of iron as compared to 35S-IRT1 and wild type. Furthermore, accumulation of metals in 35S-IRT1K146R,K171R plants was not associated with an increase in ferric chelate reductase activity; this result indicates that, at least under conditions when iron is abundant, reduction of ferric iron may not be the rate-limiting step in iron uptake by strategy I plants such as Arabidopsis.

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“…At the four-to six-true-leaf stage, seedlings were transferred to iron-sufficient plates containing 50 mM Fe(III)-EDTA or iron-deficient plates containing 300 mM ferrozine [3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine sulfonate] (HACH Chemical, Ames, IA) for 3 d. These media also contain macronutrients and micronutrients (Marschner et al, 1982), 0.7% agar and 1 mM Mes, pH 6.0. Plants were grown at 218C under constant light (;90 mEÁm ÿ2 Ás ÿ1 ) under a yellow filter (acrylic yellow-2208; Cadillac Plastic and Chemical, Pittsburgh, PA) to protect the Fe(III)-EDTA from photochemical degradation (Hangarter and Stasinopoulos, 1991). Plants used for in situ hybridization studies were germinated directly on irondeficient or iron-sufficient plates and grown vertically.…”

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

The Essential Basic Helix-Loop-Helix Protein FIT1 Is Required for the Iron Deficiency Response

2004

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Regulation of iron uptake is critical for plant survival. Although the activities responsible for reduction and transport of iron at the plant root surface have been described, the genes controlling these activities are largely unknown. We report the identification of the essential gene Fe-deficiency Induced Transcription Factor 1 (FIT1), which encodes a putative transcription factor that regulates iron uptake responses in Arabidopsis thaliana. Like the Fe(III) chelate reductase FRO2 and high affinity Fe(II) transporter IRT1, FIT1 mRNA is detected in the outer cell layers of the root and accumulates in response to iron deficiency. fit1 mutant plants are chlorotic and die as seedlings but can be rescued by the addition of supplemental iron, pointing to a defect in iron uptake. fit1 mutant plants accumulate less iron than wild-type plants in root and shoot tissues. Microarray analysis shows that expression of many (72 of 179) iron-regulated genes is dependent on FIT1. We demonstrate that FIT1 regulates FRO2 at the level of mRNA accumulation and IRT1 at the level of protein accumulation. We propose a new model for iron uptake in Arabidopsis where FRO2 and IRT1 are differentially regulated by FIT1.

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Effect of Fe-Catalyzed Photooxidation of EDTA on Root Growth in Plant Culture Media

Cited by 62 publications

References 12 publications

Overexpression of the FRO2 Ferric Chelate Reductase Confers Tolerance to Growth on Low Iron and Uncovers Posttranscriptional Control

Overexpression of the FRO2 Ferric Chelate Reductase Confers Tolerance to Growth on Low Iron and Uncovers Posttranscriptional Control

Iron-Induced Turnover of the Arabidopsis IRON-REGULATED TRANSPORTER1 Metal Transporter Requires Lysine Residues

The Essential Basic Helix-Loop-Helix Protein FIT1 Is Required for the Iron Deficiency Response

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