bHLH121 Functions as A Direct Link that Facilitates the Activation of FIT by bHLH IVc Transcription Factors for Maintaining Fe Homeostasis in Arabidopsis
| 论文编号: |
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| 作者: |
Lei RH; Li Y |
| 刊物名称: |
Molecular Plant |
| 所属学科: |
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| 论文题目英文: |
bHLH121 Functions as A Direct Link that Facilitates the Activation of FIT by bHLH IVc Transcription Factors for Maintaining Fe Homeostasis in Arabidopsis |
| 年: |
Jan 2020 |
| 卷: |
online |
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| 页: |
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| 联系作者: |
Liang G |
| 收录类别: |
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| 影响因子: |
10.812 |
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| 摘要: |
Iron (Fe) deficiency is prevalent in plants grown in neutral or alkaline soil. Plants have evolved sophisticated mechanisms that regulate Fe homeostasis, ensuring survival. In Arabidopsis FER-LIKE IRON DEFICIENCY-INDUCED TRANSCRIPTION FACTOR (FIT) is a crucial regulator of Fe deficiency response. FIT is activated indirectly by bHLH IVc transcription factors (TFs) under Fe deficiency; however, it remains unclear which protein(s) act as a linker to mediate the activation of FIT by bHLH IVc TFs. In this study, we characterize the functions of bHLH121 and demonstrate that it directly associates with the FIT promoter. We found that loss-of-function mutations of bHLH121 cause severe Fe deficiency symptoms, reduced Fe accumulation, and disrupted expression of genes associated with Fe homeostasis. Genetic analysis showed that FIT is epistatic to bHLH121 and FIT overexpression partially rescues the bhlh121 mutant. Further investigation revealed, that bHLH IVc TFs interact with and promote nuclear accumulation of bHLH121. bHLH121 has DNA-binding function and can bind the promoters of FIT and bHLH Ib genes, but we did not find that it has either direct transcriptional activation or repression activity toward FIT and bHLH Ib genes. Meanwhile, we found that bHLH121 functions downstream of and is a direct target of bHLH IVc TFs, and its expression is induced by Fe deficiency in a bHLH IVc-dependent manner. Taken together, these results establish a direct link that bHLH121 functions together with bHLH IVc TFs to mediate the activation of FIT and thus plays a pivotal role in maintaining Fe homeostasis in Arabidopsis. |
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