[Advances in plant metallothionein and its heavy metal detoxification mechanisms]

Metallothioneins, which widely distribute in eukaryotic and prokaryotic organisms, are a class of cystein-rich and heavy metal-binding proteins with low molecular weights. Many genes encoding plant metallothioneins have been cloned in the past years. There is certain progress on the expression patterns, tissue specificities and structures of these genes such as the loci of promoters and introns in chromosomes, however, their exact functions remain unknown. The expressions of many plant metallothionein genes under environmental stresses suggested that they may function in both metal chaperoning and scavenging of reactive oxygen species with their large number of cysteine residues to protect plants from oxidative damage. The classification, characteristics, gene structure of plant metallothioneins, and recent advances in heavy metal detoxification are summarized in detail.