Straightforward histochemical staining of Fe by the adaptation of an old-school technique: identification of the endodermal vacuole as the site of Fe storage in Arabidopsis embryos.

Iron (Fe) is an essential metal ion, required for basic cellular processes such as respiration, photosynthesis and cell division. Therefore, Fe has to be stored and distributed to several organelles to fulfill its roles. The molecular basis of Fe distribution is poorly understood. In this context, elemental imaging approaches are becoming essential for a better understanding of metal homeostasis in plants. Recently, several genes have been involved in Fe storage (VIT1) and remobilization (NRAMP3 and NRAMP4) in the seed of Arabidopsis, mostly with the help of sophisticated imaging techniques. We have adapted an histochemical procedure to detect Fe in plant tissues, based on Perls staining coupled to diaminobenzidine (DAB) intensification. The Perls/DAB technique, quick and inexpensive, was shown to be specific for Fe and highly sensitive. We have applied this procedure to Arabidopsis embryos and shown that Fe is stored in the vacuoles of a specific cell layer surrounding the pro-vascular system, the endodermis. Our results have revealed a new role for the endodermis in Fe storage in the embryo and established the Perls/DAB technique as a powerful tool to detect Fe in plant tissues and cells.