Genetic Engineering to Reduce Toxicity and Increase Accumulation of Toxic Metals in Plants

The most common heavy metals (HMs) contaminants are arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb). Unlike organic contaminants, HMs do not biodegrade, and persist in the environment forever. Hence, the solution to the cleanup of HMs contaminated site is their removal from the environment. Various conventional and physicochemical methods utilized for removal of HMs are expensive, inefficient, and non-eco-friendly. Nonetheless, nature and science provide new opportunities in the form of bioremediation and phytoremediation to remediate HMs contaminated soil. Phytoremediation is a perspective technology for several HMs polluted sites owing to inclusion of several integrative approaches in it, such as phytoextraction, phytostabilization, rhizofiltration, and phytovolatilization. Phytoremediation has emerged as an economic, eco-friendly, and popular remediation technology. Endophytic bacteria also play an interesting role in phytoremediation. However, phytoremediation can be limited by the small habitat range or the small size or long life cycle of plants. The precision of biotechnological approaches, mainly genetic engineering, holds potential to make rapid and significant change in plant’s growth and development. Recent researches depicted the application of molecular biology, bioinformatics, omics, and next-generation DNA sequencing technologies to gain deeper insights into the mechanisms of HM accumulation in plants. Genetic engineering has also contributed greatly in understanding the stress responses of plants to a number of HMs through functional analysis of genes. Engineered endophytes and rhizospheric bacteria have also been tested for enhancing remediation of metals for phytoremediation purposes. The risk of gene escape with engineered hyperaccumulator lines can be reduced if plant material is applied in isolated industry- or mining-impacts areas instead of agricultural areas. A novel solution can be the application of cisgenesis and intragenesis in genetic engineering. The present article discusses various aspects of genetic engineering within the scope of phytoremediation and also sheds light on future prospects for designing plants for future demands.