Biochimie et Physiologie Moléculaire des Plantes, University of Montpellier, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, SupAgro, 34060 Montpellier, France.
Departamento de Genética Molecular y Microbiología, Pontificia Universidad Católica de Chile, 8331150, Santiago, Chile.
Plant Cell. 2020 Feb;32(2):508-524. doi: 10.1105/tpc.19.00541. Epub 2019 Nov 27.
Iron (Fe) is an essential micronutrient for plant growth and development. Any defects in the maintenance of Fe homeostasis will alter plant productivity and the quality of their derived products. In Arabidopsis (), the transcription factor ILR3 plays a central role in controlling Fe homeostasis. In this study, we identified bHLH121 as an ILR3-interacting transcription factor. Interaction studies showed that bHLH121 also interacts with the three closest homologs of ILR3 (i.e., basic-helix-loop-helix 34 [bHLH34], bHLH104, and bHLH115). loss-of-function mutants displayed severe defects in Fe homeostasis that could be reverted by exogenous Fe supply. bHLH121 acts as a direct transcriptional activator of key genes involved in the Fe regulatory network, including , , , , , , and , as well as and In addition, bHLH121 is necessary for activating the expression of transcription factor gene in response to Fe deficiency via an indirect mechanism. is expressed throughout the plant body, and its expression is not affected by Fe availability. By contrast, Fe availability affects the cellular localization of bHLH121 protein in roots. Altogether, these data show that bHLH121 is a regulator of Fe homeostasis that acts upstream of FIT in concert with ILR3 and its closest homologs.
铁（Fe）是植物生长和发育所必需的微量元素。任何维持铁稳态的缺陷都会改变植物的生产力和其衍生产品的质量。在拟南芥（Arabidopsis）中，转录因子 ILR3 在控制铁稳态中起着核心作用。在这项研究中，我们鉴定出 bHLH121 是与 ILR3 相互作用的转录因子。相互作用研究表明，bHLH121 还与 ILR3 的三个最接近的同源物（即 basic-helix-loop-helix 34 [bHLH34]、bHLH104 和 bHLH115）相互作用。bHLH121 功能丧失突变体表现出严重的铁稳态缺陷，外源性铁供应可以逆转这些缺陷。bHLH121 是参与铁调控网络的关键基因的直接转录激活剂，包括、、、、、、和、以及和。此外，bHLH121 是通过间接机制激活转录因子基因在响应缺铁时表达所必需的。在整个植物体中表达，其表达不受铁可用性的影响。相比之下，铁可用性会影响 bHLH121 蛋白在根中的细胞定位。总的来说，这些数据表明 bHLH121 是铁稳态的调节剂，与 ILR3 及其最接近的同源物一起在上游作用于 FIT。
