Résumé
The plant root system is able to adapt to the availability of water and nutrients in soils. Long-term exposure of plants to iron deficiency was shown to affect primary root length and/or number and length of the lateral roots. Such modifications of the root architecture depend on the expression of root surface iron uptake genes encoding the high affinity transporter IRT1 and the Ferric reductase oxidase FRO2. To date neither the iron sensor nor the early molecular events that lead to the regulation of these genes in response to iron starvation have been documented. In this study we have investigated the early signaling of iron deprivation in roots of Arabidopsis by combining calcium imaging and mutants' analysis. We found that the root growth was rapidly enhanced when plants were transferred to iron-free medium. In order to visualize the calcium signal generated by the root upon iron deprivation, we used the genetically encoded FRET-based YC3.60 calcium reporter. We observed that a calcium wave was concomitant with the increase of root growth. This result shows that the absence of iron is able to induce calcium release within minutes and might control root growth. The calcium-dependent regulation of root growth will be investigated.