Molecular Regulation of Iron Homeostasis in Plants

Iron (Fe) is a micronutrient that is essential for plant growth and development as well as for crop productivity and the quality of their derived products. Despite its high abundance in Earth’s crust, Fe is poorly available to plants in one-third of the cultivated land. This is because at neutral to alkaline pH, Fe is mostly present in the form of oxides/hydroxides that are not readily available for plants. Nevertheless, not only Fe deficiency, but also Fe excess is detrimental to the plant. This is due to the capacity of Fe to interact with oxygen in aerobic conditions, leading to the generation of reactive oxygen species via the Fenton reaction. Therefore, to maintain optimal Fe levels in plant cells, Fe homeostasis must be tightly regulated. To this end, plants have evolved several molecular mechanisms modulating Fe uptake, partitioning, and assimilation. Within this chapter, the main strategies evolved by plants to take up Fe from soil will be first described. Then, the main molecular mechanism regulating this process will be summarized. Last, an outline will be given on how abiotic (i.e., other micro- and macronutrients) and biotic factors affect Fe homeostasis in plants.