On the way to unravel zinc hyperaccumulation in plants: a mini review.

Zinc (Zn) is an essential element for plants that can be accumulated to very high levels in shoots of some special plant species named hyperaccumulators. Various strategies have been used in recent years to unravel the molecular bases of such an unusual Zn transport and storage, especially in Brassicacea species. In these studies, several Zn transporters and chelators have been identified that exist both in sensitive and hyperaccumulating Brassicacea species allowing the construction of a general model for Zn homeostasis. However, some determinants involved in shoot Zn tolerance are still missing. We have previously shown that defensins confer Zn tolerance and have recently studied the sub-cellular localisation of a leaf A. halleri defensin. In this mini review, we explain why we propose that family 1 defensins could play a role in the protection of the endoplasmic reticulum functioning in leaves during a Zn overload.