Résumé
Iron (Fe) is an essential micronutrient for plant development. It is present in cells in the form of Fe³⁺ and Fe²⁺. Due to its redox properties, Fe is a vital cofactor in enzymes that drive essential processes such as photosynthesis and antioxidant responses. Several Fe transporters have been identified in different cell compartments suggesting that Fe is reallocated from the external environment to different locations within the cell. However, there is currently no method to visualize Fe distribution in living plant cells at a subcellular level. To overcome these limitations, we developed a method that uses specific fluorescent sensors to visualize Fe²⁺ and Fe³⁺ in the roots of both wild-type Arabidopsis and mutants with impaired Fe homeostasis [1]. This allows detection of labile Fe and its redox status in living cells. First results reveal heterogeneous distribution of Fe²⁺ and Fe³⁺ along the primary root, with distinct gradients for both forms. Confocal microscopy further enables visualization of Fe across different cell layers. In root epidermal cells, Fe appears to be polarized, which is consistent with the localization of the ferric reductase FRO2 and the high-affinity Fe transporter IRT1. Moreover, changes in Fe redox status upon external Fe supply can be monitored, highlighting dynamic fluxes in vascular tissues. In conclusion, the development of Fe sensors offers powerful tools for live-cell Fe localization, and further optimization will support future studies of Fe homeostasis across genotypes and growth conditions.Références :[1] Alcon C, Comte A, Curie C, Xiong TC. Imaging of labile Fe2+ and Fe3+ in living Arabidopsis thaliana roots. (2024) Plant Physiol.; 195(4):2520-2523. doi: 10.1093/plphys/kiae221.