Transgenic plants exhibiting enhanced phytochelatin-based heavy metal tolerance and methods of use thereof

An isolated nucleic acid encoding a variant phytochelatin synthase (PCS), wherein the synthase exhibits diminished catalytic activity relative to native, wild type synthase, wherein said PCS variant has one or more amino acid substitutions selected from

• Q48R/C144Y/G168S/W280R (SEQ ID NO:
• 18);
• S51T/N143I/N170I/H220R (SEQ ID NO:
• 17);
• E52K (SEQ ID NO:
• 3);
• A59V (SEQ ID NO:
• 4);
• S60C/S202I (SEQ ID NO:
• 10);
• D71N (SEQ ID NO:
• 5);
• R74H/S230C/L250R (SEQ ID NO:
• 16);
• F83C/N170D (SEQ ID NO:
• 14);
• C91S/A199S (SEQ ID NO:
• 13);
• V97L (SEQ ID NO:
• 2);
• V97C (SEQ ID NO:
• 6);
• C109Y(SEQ ID NO:
• 11);
• T123R/F163I (SEQ ID NO:
• 12);
• T139P (SEQ ID NO:
• 7);
• V181G (SEQ ID NO:
• 8);
• A182G/A282V/G329S (SEQ ID NO:
• 15);
• and
• Y186C (SEQ ID NO:
• 9).