Molecular mechanisms underlying heavy metal uptake, translocation and tolerance in hyperaccumulators-an analysis: Heavy metal tolerance in hyperaccumulators

Abstract Phytoremediation is an economically viable green technology that utilizes hyperaccumulator plants to remove heavy metals (HM) from the soil. Hyperaccumulators are adept at sequestering high concentrations of HM in aerial parts and intracellular detoxification of HM through cell wall binding, organic acids, chelation and sequestration. Excess HM activate oxidative stress defense mechanisms and initiate synthesis of stress-related proteins in plants. Plethora of studies have assessed the feasibility of phytoextraction and demonstrated that high biomass and metal hyperaccumulation are the two basic requirements for making the process efficient. However, biochemical pathways involved in HM uptake, translocation and sequestration in these plants are not fully understood. Thus, more fundamental understanding of the traits and mechanisms involved in hyperaccumulation is needed to optimize phytoextraction. In this review, we aim to focus on the mechanisms of uptake, transport, and accumulation of common HM such as mercury (Hg), lead (Pb), cadmium (Cd), chromium (Cr), zinc (Zn), copper (Cu) and Arsenic (As) in hyperaccumulator plants. We will also discuss prominent metallophytes and their phytoremediation strategies. This study will be helpful in understanding the pathways involved in the uptake and translocation of HM by hyperaccumulators. It would also assist in gaining knowledge about the adaptation strategy used by plants to achieve homeostasis.