Nathalie Berger, Muskan Kalra, Fei Gao, Valérie Rofidal, Vincent Demolombe, Véronique Santoni, Christian Dubos
IPSiM, CNRS, INRAE, Institut Agro, University Montpellier, Montpellier, France.
College of Agronomy, Hunan Agricultural University, Changsha, China.
Physiol Plant. 2025 May-Jun;177(3):e70336. doi: 10.1111/ppl.70336.
Iron (Fe) is an essential micronutrient for plant growth and development whose homeostasis must be tightly regulated to avoid deficiency or excess that could be detrimental to the cells. In Arabidopsis thaliana, this mechanism is regulated by a series of transcription factors that act in an intricate regulatory network among which URI/bHLH121 (UPSTREAM REGULATOR OF IRT1) plays a predominant role. Tremendous efforts were deployed to decipher the molecular mechanisms that regulate iron homeostasis in plants. Nonetheless, the nature of the long-distance signal that conveys, via the phloem sap, information on the iron status of aerial tissues to the roots in order to coordinate iron uptake with the plant needs for iron is still to be determined. With the aim to identify potential actors involved in this process, we set up a proteomic analysis of the phloem sap of wild type Arabidopsis plants and bhlh121 loss-of-function mutants grown in iron-replete and iron-deficient conditions. We found that modifications in iron availability or the loss of URI activity have a profound impact on the phloem sap protein composition. We also found that some proteins whose translocation through the phloem sap is inhibited in response to iron deficiency are also affected in bhlh121 mutants. Interestingly, we discovered that some of the genes encoding such proteins are direct targets of URI, which suggests that the encoded proteins might act as potential signaling factors to regulate root iron uptake and/or root growth.
铁（Fe）是植物生长发育所必需的微量营养素，其体内平衡必须受到严格调控，以避免出现对细胞有害的铁缺乏或铁过量情况。在拟南芥中，这一机制由一系列转录因子调控，这些转录因子在一个复杂的调控网络中发挥作用，其中URI/bHLH121（IRT1的上游调节因子）起主要作用。人们付出了巨大努力来破译植物中铁稳态的调控分子机制。然而，通过韧皮部汁液将地上组织的铁状态信息传递给根部，以便根据植物对铁的需求协调铁吸收的长距离信号的本质仍有待确定。为了识别参与这一过程的潜在因子，我们对在铁充足和铁缺乏条件下生长的野生型拟南芥植物和bhlh121功能缺失突变体的韧皮部汁液进行了蛋白质组学分析。我们发现铁可用性的改变或URI活性的丧失对韧皮部汁液蛋白质组成有深远影响。我们还发现，一些在缺铁时其通过韧皮部汁液的转运受到抑制的蛋白质在bhlh121突变体中也受到影响。有趣的是，我们发现一些编码此类蛋白质的基因是URI的直接靶标，这表明所编码的蛋白质可能作为潜在的信号因子来调节根部铁吸收和/或根生长。
