Mechanisms of Cd Hyperaccumulation and Detoxification in Heavy Metal Hyperaccumulators: How Plants Cope with Cd

Cadmium (Cd) is classified as a toxic heavy metal and is of major concern in environmental heavy metals contamination. Some special plants, referring to Cd hyperaccumulators, could accumulate ≥100 mg kg−1 Cd in their shoots without showing phytotoxicity. The mechanisms of Cd accumulation and tolerance in Cd hyperaccumulators have provoked the interest of scientists. In the latest decade, many efforts have been put in investigating the biomolecular basis of Cd hyperaccumulation and associated Cd hypertolerance, including some important heavy metal transporters correlated to Cd accumulation and ion homeostasis in plants. This review provides an overview of the main aspects involving Cd uptake, translocation, distribution in hyperaccumulators, and the evolution of Cd hyperaccumulation. Besides, the hypothesis about the physiological role of Cd may play in hyperaccumulators is also highlighted.