The rice bHLH protein OsIRO2 is an essential regulator of the genes involved in Fe uptake under Fe‐deficient conditions

Ogo, Yuko; Itai, Reiko Nakanishi; Nakanishi, Hiromi; Kobayashi, Takanori; Takahashi, Michiko; Mori, Satoshi; Nishizawa, Naoko K.

doi:10.1111/j.1365-313x.2007.03149.x

Cited by 293 publications

(287 citation statements)

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“…OsVP1, AK109920, and AK101356 were also constitutively expressed in roots and leaves, but AK072874 expression was not detected in these organs (data not shown). These results are in accordance with our previous microarray experiment using rice 22k array slides (10,11,27), which also indicated that IDEF1, in addition to OsVP1, is clearly expressed in germinating seeds (data not shown). Because of the substantial expression of IDEF1 in vegetative organs, in contrast to little expression of AK072874, which constitutes the subgroup of IDE1/Sph/RY-binding factors with IDEF1 ( Fig.…”

Section: Resultssupporting

confidence: 82%

“…For the detection of endogenous IDEF1 transcripts, rice (cv. Nipponbare) seedlings were grown hydroponically (8,10). Transgenic tobacco and rice plants were grown as described below.…”

Section: Methodsmentioning

confidence: 99%

“…Recent studies have demonstrated that a rice iron deficiencyinduced basic helix-loop-helix (bHLH) transcription factor, Os-IRO2, regulates the Strategy II-based iron deficiency response by inducing the related genes (10,11). The core sequence to which OsIRO2 binds (CACGTGG) is overrepresented in iron deficiencyinducible gene promoters in rice (10), but its actual function in a given promoter has not been confirmed.…”

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confidence: 99%

“…The core sequence to which OsIRO2 binds (CACGTGG) is overrepresented in iron deficiencyinducible gene promoters in rice (10), but its actual function in a given promoter has not been confirmed. In nongraminaceous plants, the involvement of several bHLH transcription factors in the iron deficiency response, including tomato FER and the Arabidopsis FIT (formerly FIT1/FRU/AtbHLH29), AtbHLH38, and AtbHLH39, has been reported (12)(13)(14)(15), but their functional cis sequences have not been determined.…”

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confidence: 99%

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The transcription factor IDEF1 regulates the response to and tolerance of iron deficiency in plants

Kobayashi

Ogo²,

Itai³

et al. 2007

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

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Iron is essential for most living organisms and is often the major limiting nutrient for normal growth. Plants induce iron utilization systems under conditions of low iron availability, but the molecular mechanisms of gene regulation under iron deficiency remain largely unknown. We identified the rice transcription factor IDEF1, which specifically binds the iron deficiency-responsive cis-acting element IDE1. IDEF1 belongs to an uncharacterized branch of the plant-specific transcription factor family ABI3/VP1 and exhibits the sequence recognition property of efficiently binding to the CATGC sequence within IDE1. IDEF1 transcripts are constitutively present in rice roots and leaves. Transgenic tobacco plants expressing IDEF1 under the control of the constitutive cauliflower mosaic virus 35S promoter transactivate IDE1-mediated expression only in iron-deficient roots. Transgenic rice plants expressing an introduced IDEF1 exhibit substantial tolerance to iron deficiency in both hydroponic culture and calcareous soil. IDEF1 overexpression leads to the enhanced expression of the iron deficiency-induced transcription factor gene OsIRO2, suggesting the presence of a sequential gene regulatory network. These findings reveal cis element/trans factor interactions that are functionally linked to the iron deficiency response. Manipulation of IDEF1 also provides another approach for producing crops tolerant of iron deficiency to enhance food and biomass production in calcareous soils.ABI3/VP1 ͉ iron deficiency-responsive elements ͉ mugineic acid family phytosiderophores ͉ transgenic rice M ost living organisms require iron for growth and reproduction, and the iron absorbed by plants constitutes a major iron source for animals and humans. Although abundant in mineral soils, iron is sparingly soluble under aerobic conditions at high pH. Consequently, in calcareous soils, which constitute Ϸ30% of the world's cultivated soils, plants often exhibit iron deficiency symptoms manifested as chlorosis (yellowing caused by chlorophyll deficiency), reducing crop yield and quality (1). Higher plants use two major iron uptake strategies under conditions of low iron supply: reduction (Strategy I) and chelation (Strategy II) (2). The Strategy II mechanism is specific to graminaceous plants and is mediated by natural iron chelators, the mugineic acid family phytosiderophores (MAs) (3). Extensive physiological, biochemical, and molecular studies have identified the biosynthetic pathway of MAs and the genes encoding the biosynthetic enzymes (4-9). The expression of these biosynthetic genes is coordinately upregulated in response to iron deficiency (6,8,9), but the molecular mechanisms regulating these iron deficiency-induced genes are poorly understood.Recent studies have demonstrated that a rice iron deficiencyinduced basic helix-loop-helix (bHLH) transcription factor, Os-IRO2, regulates the Strategy II-based iron deficiency response by inducing the related genes (10, 11). The core sequence to which OsIRO2 binds (CACGTGG) is overrepresented in...

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Section: Resultssupporting

confidence: 82%

“…For the detection of endogenous IDEF1 transcripts, rice (cv. Nipponbare) seedlings were grown hydroponically (8,10). Transgenic tobacco and rice plants were grown as described below.…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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The transcription factor IDEF1 regulates the response to and tolerance of iron deficiency in plants

Kobayashi

Ogo²,

Itai³

et al. 2007

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

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201

219

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“…OsIRO2, which is induced by Fe deficiency and is positively regulated by IDEF1, binds to the CACGTGG element to activate another subset of Fe-deficiencyresponsive genes, including two transcription factor genes: OsNAC4 and the AP2 domain-containing gene. These transcription factors may then regulate Fe-deficiency-responsive genes lacking IDEs and CACGTGG in their promoter regions [44]. The induced expression of IDEF1 in transgenic rice plants would effectively strengthen the overall regulatory pathway to confer tolerance to Fe deficiency.…”

Section: Nt Line13 Line12mentioning

confidence: 99%