Heavy metal detoxification in plants: Phytochelatin biosynthesis and function

Phytochelatins (PCs) are a family of peptides important in the detoxification of heavy metals such as cadmium in plants and some microorganisms. PCs are synthesised enzymatically from glutathione. Molecular genetic studies, particularly in the yeast Schizosaccharomyces pombe and in the plant Arabidopsis thaliana, have identified a number of genes important in the biosynthesis or function of PCs. PC-deficient mutants of Arabidopsis have confirmed both the role of glutathione as the substrate for PC biosynthesis and the role of PCs themselves in heavy metal detoxification in plants. PC synthase genes have been identified in Arabidopsis and other plant species as well as in a number of animal species, suggesting PCs play a wider role in metal detoxification than previously anticipated. PC synthesis is regulated at a number of levels, most importantly through the activation of PC synthase by metal ions. This article reviews recent advances in our understanding of the biosynthesis and function of PCs in plants and other organisms.