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, i...
