Overexpression of the maize phytochelatin synthase gene (ZmPCS1) enhances Cd tolerance in plants

Phytochelatin synthase (PCS) catalyzes the biosynthesis of phytochelatins (PCs), which play an essential role in detoxification of heavy metals in plants and other living organisms. In this study, we investigated the roles of the maize phytochelatin synthase gene ZmPCS1 in cadmium (Cd) tolerance. Induced expression results showed that expression of ZmPCS1 was upregulated under Cd stress in maize leaves and roots. Moreover, ZmPCS1 repaired the defective phenotypes resulting from heteroexpression of ZmPCS1 in the Cd-sensitive yeast mutant ∆ycf1 and Arabidopsis AtPCS1-deficent mutant atpcs1 under Cd stress. Moreover, overexpression in Arabidopsis also enhanced Cd tolerance and accumulation. Further analysis suggested that this increase in tolerance was due to increases in glutathione and PC contents, and a decrease in reactive oxygen species accumulation. Meanwhile, transient expression of ZmPCS1 in tobacco leaves was also found to cause a decrease in Cd toxicity. Taken together, these results suggest that the maize ZmPCS1 gene plays an important role in Cd tolerance in yeast and plants, and could, therefore, serve as a promising candidate in future breeding programs in crops.