FIT interacts with AtbHLH38 and AtbHLH39 in regulating iron uptake gene expression for iron homeostasis in Arabidopsis

Yuan, Youxi; Wu, Huilan; Wang, Ning; Li, Jie; Zhao, Weina; Du, Juan; Wang, Daowen; Ling, Hong

doi:10.1038/cr.2008.26

Cited by 528 publications

(589 citation statements)

References 41 publications

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“…The FIT basic helix-loop-helix (bHLH) transcription factor controls the transcription of FRO2 and partly that of IRT1 in response to iron starvation in Arabidopsis (Colangelo and Guerinot, 2004;Jakoby et al, 2004;Yuan et al, 2005). FIT directly binds to FRO2 and IRT1 promoters in yeast, presumably through E-box motifs presents in both promoters (Colangelo and Guerinot, 2004;Jakoby et al, 2004;Yuan et al, 2008). Consistently, a fit loss-of-function mutant displays low FRO2 and IRT1 expression in roots (Colangelo and Guerinot, 2004;Jakoby et al, 2004;Yuan et al, 2005).…”

Section: Introductionmentioning

confidence: 70%

“…However, constitutive expression of FIT is not sufficient to further upregulate FRO2 and IRT1 in irondeficient roots, or to induce FRO2 and IRT1 mRNA accumulation under iron-sufficient conditions (Colangelo and Guerinot, 2004;Jakoby et al, 2004;Yuan et al, 2005). FIT has been shown to heterodimerize with two other ironregulated bHLH transcription factors, bHLH38 and bHLH39, to induce expression of the iron-uptake machinery (Yuan et al, 2008). Interestingly, the master regulator FIT is itself transcriptionally regulated by iron starvation, leading to an increase in FIT mRNA level in the root epidermis (Colangelo and Guerinot, 2004;Jakoby et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

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Proteasome‐mediated turnover of the transcriptional activator FIT is required for plant iron‐deficiency responses

et al. 2011

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SUMMARYPlants display a number of responses to low iron availability in order to increase iron uptake from the soil. In the model plant Arabidopsis thaliana, the ferric-chelate reductase FRO2 and the ferrous iron transporter IRT1 control iron entry from the soil into the root epidermis. To maintain iron homeostasis, the expression of FRO2 and IRT1 is tightly controlled by iron deficiency at the transcriptional level. The basic helix-loop-helix (bHLH) transcription factor FIT represents the most upstream actor known in the iron-deficiency signaling pathway, and directly regulates the expression of the root iron uptake machinery genes FRO2 and IRT1. However, how FIT is controlled by iron and acts to activate transcription of its targets remains obscure. Here we show that FIT mRNA and endogenous FIT protein accumulate in Arabidopsis roots upon iron deficiency. However, using plants constitutively expressing FIT, we observed that FIT protein accumulation is reduced in iron-limited conditions. This post-transcriptional regulation of FIT is perfectly synchronized with the accumulation of endogenous FIT and IRT1 proteins, and therefore is part of the early responses to low iron. We demonstrated that such regulation affects FIT protein stability under iron deficiency as a result of 26S proteasome-dependent degradation. In addition, we showed that FIT post-translational regulation by iron is required for FRO2 and IRT1 gene expression. Taken together our results indicate that FIT transcriptional and post-translational regulations are integrated in plant roots to ensure that the positive regulator FIT accumulates as a short-lived protein following iron shortage, and to allow proper iron-deficiency responses.

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Section: Introductionmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Proteasome‐mediated turnover of the transcriptional activator FIT is required for plant iron‐deficiency responses

et al. 2011

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“…We tested if MED25 interacted with transcription factors involved in the regulation of iron homeostasis in Arabidopsis, i.e., FIT, PYE, bHLH038, bHLH039, EIN3 and EIL1 (Colangelo and Guerinot, 2004;Yuan et al, 2008;Long et al, 2010;Lingam et al, 2011). We found that MED25 interacted directly with EIN3 and EIL1, whereas YID1/ MED16 showed no interaction (Figure 5a).…”

Section: Med25 But Not Yid1/med16 Interacts With the Transcription Famentioning

confidence: 97%

“…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%

“…The role of FIT is in iron homeostasis, regulating the expression of IRT1 and FRO2 in species of Arabidopsis and tomato (Ling et al, 2002;Colangelo and Guerinot, 2004;Jakoby et al, 2004;Yuan et al, 2005). Yuan et al (2008) and Wang et al (2012) proposed that FIT forms a complex with other iron-deficiencyinduced bHLH transcription factors such as bHLH38, bHLH39, bHLH100 and bHLH101. Recently, two transcription factors ethylene-insensitive 3 (EIN3) and ethyleneinsensitive 3-like 1 (EIL1) in the ethylene signaling pathway were shown to be involved in the regulation of iron homeostasis.…”

Section: Introductionmentioning

confidence: 99%

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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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Iron Uptake by Plants and Fungi

Crichton

2009

Iron Metabolism

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FIT interacts with AtbHLH38 and AtbHLH39 in regulating iron uptake gene expression for iron homeostasis in Arabidopsis

Cited by 528 publications

References 41 publications

Proteasome‐mediated turnover of the transcriptional activator FIT is required for plant iron‐deficiency responses

Proteasome‐mediated turnover of the transcriptional activator FIT is required for plant iron‐deficiency responses

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

Iron Uptake by Plants and Fungi

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