Cloning and characterization of a Phragmites australis phytochelatin synthase (PaPCS) and achieving Cd tolerance in tall fescue.

The production of phytochelatins (PCs) provides an important means for plants to achieve tolerance to cadmium (Cd) toxicity. A reed gene encoding PC synthase (PaPCS) was isolated and its function tested through its heterologous expression in a strain of yeast sensitive to Cd. Subsequently, the Cd sensitive and high biomass accumulating species tall fescue was transformed either with PaPCS or PaGCS (a glutamyl cysteine synthetase gene of reed) on their own (single transformants), or with both genes together in the same transgene cassette (double transformant). The single and double transformants showed greater Cd tolerance and accumulated more Cd and PC than wild type plants, and their Cd leaf/root ratio content was higher. The ranking in terms of Cd and PC content for the various transgenic lines was double transformants>PaGCS single transformants>PaPCS single transformants>wild type. Thus PaGCS appears to exert a greater influence than PaPCS over PC synthesis and Cd tolerance/accumulation. The double transformant has interesting potential for phytoremediation.