The metal ion transporter IRT1 is necessary for iron homeostasis and efficient photosynthesis in <i>Arabidopsis thaliana</i>

Varotto, Claudio; Maiwald, Daniela; Pesaresi, Paolo; Jahns, Peter; Salamini, F.; Leister, Dario

doi:10.1046/j.1365-313x.2002.01381.x

Cited by 296 publications

(244 citation statements)

References 55 publications

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“…A similar growth phenotype was previously reported for the irt1 mutant (Henriques et al, 2002;Varotto et al, 2002;Vert et al, 2002), suggesting that FIT1 may regulate IRT1 activity because the two mutants share the same growth phenotype. We show that fit1-1 plants are unable to induce Fe(III) chelate reductase and Fe(II) transport activities (Figures 1 and 4).…”

Section: Discussionsupporting

confidence: 85%

“…The inducible ferric chelate reductase activity of FRO2 reduces Fe(III) to Fe(II) (Robinson et al, 1999), which was recently shown to be the rate limiting step for iron acquisition from the soil (Connolly et al, 2003). Fe(II) is then transported into the plant by IRT1 (Eide et al, 1996), which is the major iron transporter of the plant root (Henriques et al, 2002;Varotto et al, 2002;Vert et al, 2002). The grasses (Takagi et al, 1984), as well as species of bacteria and fungi (Guerinot, 1994), use the Strategy II response, which relies on chelation of Fe(III) rather than reduction.…”

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: 85%

Section: Introductionmentioning

confidence: 99%

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

2004

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“…During iron uptake in Arabidopsis, the bHLH transcription factor FIT, the master regulator, forms heterodimers with other bHLH proteins to regulate the ferrous iron transporter IRT1 and the ferric-chelate reductase FRO2 in response to iron deficiency in plants (Robinson et al, 1999;Varotto et al, 2002;Vert et al, 2002;Connolly et al, 2003;Colangelo and Guerinot, 2004;Yuan et al, 2008;Wang et al, 2012). Our data support that FIT, rather than the interacting proteins bHLH38 or bHLLH39, plays a significant role in regulation of iron homeostasis in the yid1/med16 or med25 mutants ( Figure S6), since the induction of the two genes encoding FIT-interacting-protein, bHLH38 and bHLH39, was unaffected under iron-deficient conditions in the yid1/med16 or med25 mutants.…”

Section: Discussionmentioning

confidence: 99%

“…However, the IRT1 protein is not specific for iron. Other metals such as Zn 2+ , Mn 2+ and Co 2+ can be transported into plants via the IRT1 protein in Arabidopsis (Eide et al, 1996;Korshunova et al, 1999;Connolly et al, 2002;Henriques et al, 2002;Varotto et al, 2002;Vert et al, 2002). Following transportation into root cells, iron is chelated by citrate or nicotianamine and distributed to the shoots (Stephan and Scholz, 1993;Briat et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

The Arabidopsis Mediator subunit MED16 regulates iron homeostasis by associating with EIN3/EIL1 through subunit MED25

et al. 2014

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These authors contributed equally to this work. SUMMARYIron is an essential micronutrient for plants and animals, and plants are a major source of iron for humans. Therefore, understanding the regulation of iron homeostasis in plants is critical. We identified a T-DNA insertion mutant, yellow and sensitive to iron-deficiency 1 (yid1), that was hypersensitive to iron deficiency, containing a reduced amount of iron. YID1 encodes the Arabidopsis Mediator complex subunit MED16. We demonstrated that YID1/MED16 interacted with another subunit, MED25. MED25 played an important role in regulation of iron homeostasis by interacting with EIN3 and EIL1, two transcription factors in ethylene signaling associated with regulation of iron homeostasis. We found that the transcriptome in yid1 and med25 mutants was significantly affected by iron deficiency. In particular, the transcription levels of FIT, IRT1 and FRO2 were reduced in the yid1 and med25 mutants under iron-deficient conditions. The finding that YID1/MED16 and MED25 positively regulate iron homeostasis in Arabidopsis increases our understanding of the complex transcriptional regulation of iron homeostasis in plants.

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“…While spraying with ferric ammonium significantly improved growth and chlorophyll biosynthesis in the irt1-1 mutant (Varotto et al, 2002), this treatment had no effect on atm3-1 seedlings (Fig. 5C).…”

Section: Atm3 Plays a Minor Role In Metal Homeostasismentioning

confidence: 94%

An Allelic Mutant Series of ATM3 Reveals Its Key Role in the Biogenesis of Cytosolic Iron-Sulfur Proteins in Arabidopsis

et al. 2009

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The ATP-binding cassette transporters of mitochondria (ATMs) are highly conserved proteins, but their function in plants is poorly defined. Arabidopsis (Arabidopsis thaliana) has three ATM genes, namely ATM1, ATM2, and ATM3. Using a collection of insertional mutants, we show that only ATM3 has an important function for plant growth. Additional atm3 alleles were identified among sirtinol-resistant lines, correlating with decreased activities of aldehyde oxidases, cytosolic enzymes that convert sirtinol into an auxin analog, and depend on iron-sulfur (Fe-S) and molybdenum cofactor (Moco) as prosthetic groups. In the sirtinol-resistant atm3-3 allele, the highly conserved arginine-612 is replaced by a lysine residue, the negative effect of which could be mimicked in the yeast Atm1p ortholog. Arabidopsis atm3 mutants displayed defects in root growth, chlorophyll content, and seedling establishment. Analyses of selected metal enzymes showed that the activity of cytosolic aconitase (Fe-S) was strongly decreased across the range of atm3 alleles, whereas mitochondrial and plastid Fe-S enzymes were unaffected. Nitrate reductase activity (Moco, heme) was decreased by 50% in the strong atm3 alleles, but catalase activity (heme) was similar to that of the wild type. Strikingly, in contrast to mutants in the yeast and mammalian orthologs, Arabidopsis atm3 mutants did not display a dramatic iron homeostasis defect and did not accumulate iron in mitochondria. Our data suggest that Arabidopsis ATM3 may transport (1) at least two distinct compounds or (2) a single compound required for both Fe-S and Moco assembly machineries in the cytosol, but not iron.

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The metal ion transporter IRT1 is necessary for iron homeostasis and efficient photosynthesis in Arabidopsis thaliana

Cited by 296 publications

References 55 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 Arabidopsis Mediator subunit MED16 regulates iron homeostasis by associating with EIN3/EIL1 through subunit MED25

An Allelic Mutant Series of ATM3 Reveals Its Key Role in the Biogenesis of Cytosolic Iron-Sulfur Proteins in Arabidopsis

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