ABSTRACT
Heavy metal tolerance is an adaptation of plants to the terrestrial environment. Since most plants rely on the soil for nutrients and water, mechanisms to neutralize the effects of leached heavy metals on plant metabolism evolved. Chelation by heavy metal-binding ligands is the most common way plants respond to heavy metal toxicity. Phytochelatins (PCs) are cysteine-rich peptide ligands found in plants and yeast that bind and sequester toxic metal ions into vacuoles to detoxify the plant cells. Mounting evidence suggests that numerous plants are able to produce PCs. However, constitutively expressed PC synthase (PCs)-like genes were also reported in certain animals, but there is no evidence of animal gene products with PC functions, suggesting roles other than PC biosynthesis. PCs, glutathione, and O-acetyl-L-serine influence hyperaccumulation of heavy metals in certain plants. The ability of plants to clean up heavy metals from the soil and water contributes to phytoremediation in metal contaminated areas.
