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

1. 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).

2. The isolated nucleic acid encoding the PCS of claim 1 , wherein said variant comprises a Y186C (SEQ ID NO: 9) substitution.

3. An isolated nucleic acid encoding a plant PCS of claim 1 , wherein said variant comprises a C109Y (SEQ ID NO: 11) substitution.

4. The isolated nucleic acid of claim 1 , wherein the nucleic acid further comprises a reporter nucleic acid covalently linked thereto.

5. The isolated nucleic acid of claim 4 , said reporter nucleic acid encoding a reporter polypeptide selected from the group consisting of a FLAG octapeptide, a human influenza virus hemagglutinin epitope, a β-glucuronidase epitope, a green fluorescent protein epitope, and a luciferase epitope.

6. A recombinant cell comprising the isolated nucleic acid of claim 1 .

7. The cell of claim 6 , wherein said cell is selected from the group consisting of a prokaryotic cell and a eukaryotic cell.

8. A vector encoding at least one PCS variant as claimed in claim 1 .

9. A transgenic plant stably transformed with an isolated nucleic acid encoding a variant PCS as claimed in claim 8 .

10. A method of generating a transgenic heavy metal resistant plant comprising introducing into the cells of the plant an isolated nucleic acid of claim 1 , encoding said variant PCS, thereby generating a transgenic heavy metal resistant plant.

11. A method of decreasing the level of a heavy metal in a harvestable portion of a plant, said method comprising expressing the nucleic acid of claim 1 encoding said variant PCS in a non-harvestable portion of a plant, thereby decreasing the level of heavy metal in the harvestable portion of the plant.

12. A method of removing a heavy metal from groundwater, said method comprising growing in said groundwater the transgenic of claim 9 , and harvesting said plant from said groundwater, thereby removing said heavy metal from said groundwater.

13. Transgenic cells, seeds or progeny of the stably transformed plant of claim 9 , each of which comprise the isolated nucleic acid encoding said variant PCS.

14. A transgenic plant comprising the isolated nucleic acid of claim 2 .

15. A transgenic plant comprising the isolated nucleic acid of claim 3 .