The role of transition metal homeostasis in plant seed development

For human health, transition metal accumulation in edible seeds like cereal grains is of worldwide importance, since Fe and Zn deficiencies are among the most prevalent human nutritional disorders in the world. There have been many recent developments in our understanding of the patterns in which transition metals accumulate in the seeds, the identity of some specific transporters that are required for efficient seed metal accumulation, and the central role played by the ubiquitous plant metal chelator nicotianamine (NA). These and other recent discoveries will be reviewed here.

► Plants flexibly move transition metals by continuous uptake or by re-translocation, depending on nutritional status.
► The metal chelator nicotianamine is essential for efficient loading of transition metals into flowers and seeds.
► In seeds, Fe is not bound to ferritin, as previously believed, but localizes instead in vacuoles.
► To enable strategies to enhance metal accumulation in seeds, the transporters at loading bottlenecks must be identified.