Genetics of Metal Tolerance and Accumulation in Higher Plants

Abstract Phytoremediation of metals is rapidly developing as a cost‐effective and environmentally friendly solution for cleaning up heavy‐metal‐contaminated sites. The most important requirements for effective phytoremediation are fast‐growing, high biomass plants that uptake and accumulate large amounts of toxic metals in their aboveground harvestable parts. A relatively small group of hyperaccumulator plants sequesters metals in their shoot tissues at high concentrations. In recent years, major scientific progress has been made in understanding the physiological mechanisms of metal uptake and transport in these plants. The majority of metal hyperaccumulators are slow growing and typically have low biomass, so bioengineering of nonaccumulators that have high biomass is essential for more effective phytoremediation. Biotechnology offers the opportunity to transfer hyperaccumulator phenotypes into fast‐growing, high biomass plants that could be highly effective in phytoremediation. However, comprehensive knowledge of the genetics of metal tolerance and accumulation is essential to design transgenic plants capable of phytoremediation. After an initial focus on plants with an immediate promise of application, research is now being directed at understanding the underlying mechanisms involved in heavy metal hyperaccumulation in plants. Once the rate‐limiting steps for uptake, translocation, and detoxification of metals in hyperaccumulator plants are identified, more informed construction of transgenic plants could become rather routine, which will help tremendously in more effective use of phytoremediation technology for cleaning up heavy‐metal‐contaminated sites.