Roles of Brassicaceae in Phytoremediation of Metals and Metalloids

Heavy metals and metalloids in trace amounts are natural components of environment. Their excessive addition by anthropogenic means posed a serious threat to the stability of ecosystem. Recent concerns of environmental contamination have initiated the development of appropriate technologies for removing or reducing such toxicants from different components of environment. Plants that accumulate greater than 0.1 % metals in leaves or other tissues without showing any visible toxicity symptoms are categorised as hyperaccumulators. These plants may be used as cost-effective and eco-friendly remediators at contaminated sites. In the present review, the key roles of several species of family Brassicaceae have been highlighted with species-level mechanism of phytoremediation. About (25 %) members of the Brassicaceae comprising of about 90 species are metal hyperaccumulators discovered worldwide to date. These Brassicaceae members are potential candidates for phytoremediation technologies. Of these 90 metal hyperaccumulators, species of the genera such as Alyssum, Arabidopsis, Noccaea and Brassica have been studied extensively for their ability to hyperaccumulate, remove, destroy, degrade, sequester, transform, assimilate, metabolise or detoxify majority of trace metals and appear to be model phytoremediators. These species are also attractive candidates for developing transgenics by introducing relevant genes to improve their applicability for phytoremediation. In this review, we elucidate the diversity and role of some of the Brassicaceae members in remediating contaminated sites worldwide and also highlighted the physiological mechanisms of uptake and tolerance, the genetic basis for the metal tolerance mechanisms.