A New Tomato Mutant Inefficient in the Transport of Iron

Brown, J. C.; Chaney, Rufus L.; Ambler, J. E.

doi:10.1111/j.1399-3054.1971.tb01086.x

Cited by 134 publications

(72 citation statements)

References 10 publications

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“…Because of sequence similarity outside of the bHLH motif, FIT1 is the Arabidopsis protein most closely related to the FER protein of tomato. As described here, the chlorotic and lethal phenotype of fit1 plants correlates with the description previously given for the fer mutant (Brown et al, 1971;Ling et al, 2002). We have shown that FIT1 message accumulates to higher levels under iron-deficient growth conditions than under iron-sufficient growth conditions in roots ( Figure 1A).…”

Section: Discussionsupporting

confidence: 56%

“…The FER mutant was initially characterized as being unable to induce Strategy I responses under iron deficiency (Brown et al, 1971;Brown and Ambler, 1974). Grafting experiments have shown that the fer gene is required in roots but not in shoots (Brown et al, 1971). Recent cloning of the fer gene reveals that it encodes a basic helix-loophelix (bHLH) putative transcription factor (Ling et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Discussionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

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

2004

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“…The most promising clues on the regulation of strategy I are expected from the identification of the fer gene. The fer (T3238fer) mutant is not able to switch on strategy I responses after iron deficiency, such as enhanced extrusion of protons and Fe(III)-chelate reductase activity in the root (15,16). Reciprocal grafting of the mutant to a wild type indicated that the fer gene is required in roots but not in shoots (15).…”

mentioning

confidence: 99%

The tomato fer gene encoding a bHLH protein controls iron-uptake responses in roots

Ling

Bauer²,

Bereczky³

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

358

334

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Iron deficiency is among the most common nutritional disorders in plants. To cope with low iron supply, plants with the exception of the Gramineae increase the solubility and uptake of iron by inducing physiological and developmental alterations including iron reduction, soil acidification, Fe(II) transport and root-hair proliferation (strategy I). The chlorotic tomato fer mutant fails to activate the strategy I. It was shown previously that the fer gene is required in the root. Here, we show that fer plants exhibit root developmental phenotypes after low and sufficient iron nutrition indicating that FER acts irrespective of iron supply. Mutant fer roots displayed lower Leirt1 expression than wild-type roots. We isolated the fer gene by map-based cloning and demonstrate that it encodes a protein containing a basic helix-loop-helix domain. fer is expressed in a cell-specific pattern at the root tip independently from iron supply. Our results suggest that FER may control root physiology and development at a transcriptional level in response to iron supply and thus may be the first identified regulator for iron nutrition in plants.

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“…A promising clue about signaling components involved in iron acquisition was recently derived from the molecular identification of the tomato fer gene encoding a root-specific bHLH protein (25). The tomato fer mutant is unable to develop physiological and morphological iron-deficiency responses such as iron reduction and induced Leirt1 transporter gene expression in roots and accumulates less iron than wild type, leading to severe chlorosis (25)(26)(27). The fer gene seems to be required for sensing iron availability in the root tip and subsequently regulating the appropriate physiological and morphological responses (25).…”

mentioning

confidence: 99%

Differential Regulation of nramp and irt Metal Transporter Genes in Wild Type and Iron Uptake Mutants of Tomato

Bereczky

Wang

Schubert

et al. 2003

Journal of Biological Chemistry

180

149

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Metal transporters regulated by iron can transport a variety of divalent metals, suggesting that iron regulation is important for specificity of iron transport. In plants, the iron-regulated broad-range metal transporter IRT1 is required for uptake of iron into the root epidermis. Functions of other iron-regulated plant metal transporters are not yet established. To deduce novel plant iron transport functions we studied the regulation of four tomato metal transporter genes belonging to the nramp and irt families with respect to environmental and genetic factors influencing iron uptake. We isolated Lenramp1 and Lenramp3 from tomato and demonstrate that these genes encode functional NRAMP metal transporters in yeast, where they were iron-regulated and localized mainly to intracellular vesicles. Lenramp1 and Leirt1 revealed both root-specific expression and up-regulation by iron deficiency, respectively, in contrast to Leirt2 and Lenramp3. Lenramp1 and Leirt1, but not Lenramp3 and Leirt2, were down-regulated in the roots of fer mutant plants deficient in a bHLH gene regulating iron uptake. In chloronerva mutant plants lacking the functional enzyme for synthesis of the plant-specific metal chelator nicotianamine Leirt1 and Lenramp1 were up-regulated despite sufficient iron supply independent of a functional fer gene. Lenramp1 was expressed in the vascular root parenchyma in a similar cellular pattern as the fer gene. However, the fer gene was not sufficient for inducing Lenramp1 and Leirt1 when ectopically expressed. Based on our results, we suggest a novel function for NRAMP1 in mobilizing iron in the vascular parenchyma upon iron deficiency in plants. We discuss fer/nicotianamine synthase-dependent and -independent regulatory pathways for metal transporter gene regulation.

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A New Tomato Mutant Inefficient in the Transport of Iron

Cited by 134 publications

References 10 publications

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

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

The tomato fer gene encoding a bHLH protein controls iron-uptake responses in roots

Differential Regulation of nramp and irt Metal Transporter Genes in Wild Type and Iron Uptake Mutants of Tomato

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