Phytoremediation of heavy metal(loid)s with integral involvement of the endogenous metal-chelators: present state-of-the-art and future prospect

Heavy metals(loid)s (HMs) threaten ecosystems and human health worldwide. Organic and inorganic compounds of different HMs are released, converted, and accumulated in different environmental spheres, significantly polluting soil, water, and food chains. In recent times, ‘phytoremediation’ which can be scaled easily and may not demand as much technical oversight as traditional methods, is considered to be an environment-friendly and sustainable method of pollutant’ (including heavy metals) removal from contaminated soil and water, and therefore, is a better alternative compared to the capital and energy intensive conventional strategies. Phytoremediation is performed by the hyperaccumulator plants, which have an appreciable stress tolerance potential. Primarily, the hyperaccumulating plants absorb contaminants through the roots and translocate them to the aerial parts. Hyperaccumulators have certain genetic characteristics that can increase heavy metal absorption from soil and water. Phytochelatin, ATPase, and metallothionein facilitate this process. Phytochelatins are small peptides that help to prepare the cell for the uptake and detoxication of metals and metalloids at inter- and intracellular levels. They form stable complexes with metal(loid)s by chelation inside the cells and subsequent sequestration into vacuoles. Scientists are manipulating the genetics of hyperaccumulators in many ways to accelerate the process in specific periods. This review attempts to give a comprehensive account of the mechanism of phytochelatin action and prospects that hold the hidden truth and immense potential for accomplishing the phytoremediation of HMs from the contaminated soil environment.