IRON MAN interacts with BRUTUS to maintain iron homeostasis in Arabidopsis
IRON MAN interacts with BRUTUS to maintain iron homeostasis in Arabidopsis
复制标题
铁人与BRUTUS相互作用以维持拟南芥的铁稳态
DOI：
10.1073/pnas.2109063118
复制
发表时间：
2021-09-28
影响因子：
11.1
通讯作者：
Liang, Gang
中科院分区：
文献类型：
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作者：
Li, Yang;Lu, Cheng Kai;Liang, Gang
IRON MAN（IMA）肽是一类控制植物体内铁转运的小肽，但其在铁信号转导中的作用尚不清楚。BRUTUS（BTS）是一种潜在的铁传感器，通过促进泛素介导的bHLH 105和bHLH 115（铁缺乏反应的两种正调节剂）降解来负调节铁稳态。在这里，我们表明IMA肽与BTS相互作用。IMA肽的C末端部分含有保守的BTS相互作用结构域（BID），其负责它们与BTS的C末端的相互作用。组成型表达IMA基因的拟南芥植物表型复制了bts-2突变体。此外，IMA肽被BTS泛素化和降解。bHLH 105和bHLH 115还共享BID，这说明了它们与BTS的交互。IMA肽与bHLH 105/bHLH 115竞争与BTS的相互作用，从而抑制BTS对这些转录因子的降解。遗传分析表明bHLH 105/bHLH 115和IMA 3在BTS下游具有相加作用和功能。此外，BTS和IMA 3的转录在铁缺乏条件下直接被bHLH 105和bHLH 115激活。我们的研究结果提供了一个概念框架，了解铁稳态的调节：IMA肽保护bHLH 105/bHLH 115从降解螯合BTS，从而激活缺铁反应。
IRON MAN (IMA) peptides, a family of small peptides, control iron (Fe) transport in plants, but their roles in Fe signaling remain unclear. BRUTUS (BTS) is a potential Fe sensor that negatively regulates Fe homeostasis by promoting the ubiquitin-mediated degradation of bHLH105 and bHLH115, two positive regulators of the Fe deficiency response. Here, we show that IMA peptides interact with BTS. The C-terminal parts of IMA peptides contain a conserved BTS interaction domain (BID) that is responsible for their interaction with the C terminus of BTS. Arabidopsis thaliana plants constitutively expressing IMA genes phenocopy the bts-2 mutant. Moreover, IMA peptides are ubiquitinated and degraded by BTS. bHLH105 and bHLH115 also share a BID, which accounts for their interaction with BTS. IMA peptides compete with bHLH105/bHLH115 for interaction with BTS, thereby inhibiting the degradation of these transcription factors by BTS. Genetic analyses suggest that bHLH105/bHLH115 and IMA3 have additive roles and function downstream of BTS. Moreover, the transcription of both BTS and IMA3 is activated directly by bHLH105 and bHLH115 under Fe-deficient conditions. Our findings provide a conceptual framework for understanding the regulation of Fe homeostasis: IMA peptides protect bHLH105/bHLH115 from degradation by sequestering BTS, thereby activating the Fe deficiency response.