Comparative understanding of metal hyperaccumulation in plants: a mini-review.

Hyperaccumulator plants are ideal models for investigating the regulatory mechanisms of plant metal homeostasis and environmental adaptation due to their notable traits of metal accumulation and tolerance. These traits may benefit either the biofortification of essential mineral nutrients or the phytoremediation of nonessential toxic metals. A common mechanism by which elevated expression of key genes involved in metal transport or chelation contributes to hyperaccumulation and hypertolerance was proposed mainly from studies examining two Brassicaceae hyperaccumulators, namely Arabidopsis halleri and Noccaea caerulescens (formerly Thlaspi caerulescens). Meanwhile, recent findings regarding systems outside the Brassicaceae hyperaccumulators indicated that functional enhancement of key genes might represent a strategy evolved by hyperaccumulator plants. This review provides a brief outline of metal hyperaccumulation in plants and highlights commonalities and differences among various hyperaccumulators.