Transgenic Approaches to Improve Phytoremediation of Heavy Metal Polluted Soils

Use of plants to remediate soil contaminated with heavy metals has received an increasing attention during the last decade. Bioremediation using living plant species, referred to as phytoremediation, covers several different strategies, of which bioremediation employs phytoextraction, rhizofiltration, phytostabilization, and phytovolatilization. High efficiency, low cost, and easy operation make phytoremediation an important alternative to current physicochemical methods. Although, a number of metal-hyperaccumulating plant species have been identified, they have little significance in direct application because of their slow growth, low biomass, and intense interaction with a specific habitat. The phytoremediation potential of plants with well-established agricultural properties and high-biomass yield can be substantially improved by genetic manipulations. The transgenic approaches involve implementation of heterologous metal transporters, centrally important in metal uptake, compartmentalization and/or translocation to organs, improved production of intracellular metal-detoxifying chelators, and (over)production of novel enzymes. Efforts are also being directed to obtain better molecular insights into metallomics and physiology of hyperaccumulating plants, which is likely to provide candidate genes suitable for phytoremediation. Although substantial progress has been made, further efforts require interdisciplinary approach and, more so, field trials are needed to assess the risk of genetic pollution and underlying economics. Here, we discuss the evidence supporting suitability and prospects of transgenic approaches in phytoremediation of heavy metal-contaminated soils.