Role of pCeMT, a putative metallothionein from Colocasia esculenta, in response to metal stress.

Metallothioneins (MTs) play a major role in metal homeostasis and/or detoxification in plants. In this study, a novel gene, pCeMT, was isolated from Colocasia esculenta and characterized. Our results indicate that Escherichia coli cells expressing pCeMT exhibited enhanced Cd, Cu, and Zn tolerance and accumulation compared with control cells. Furthermore, pCeMT-overexpressing tobacco seedlings displayed better growth under Cd, Cu, and Zn stresses and accumulated more Cd and Zn compared with the wild type. Interestingly, transgenic tobacco displayed markedly decreased hydrogen peroxide (H(2)O(2)) and lipid peroxidation levels under Cd, Cu, and Zn treatments. These results suggest that pCeMT could play an important role in the protection of plant cells from oxidative stress by reactive oxygen species (ROS) scavenging and in the detoxification of free metals by metal binding, leading to improved plant metal tolerance.