The present disclosure provides methods, recombinant DNA molecules, recombinant host cells containing the DNA molecules, and transgenic plant cells, plant tissue and plants which contain and express at least one phytochelatin biosynthetic coding sequence under the regulatory control of the strong ACT2 constitutive promoter or the light-inducible SRS1 promoter and/or a plant-expressible arsenate reductase coding sequence. Optionally the plant expressing the at least one phytochelatin biosynthetic enzyme coding sequence can also express a mercuric ion reductase coding sequence. The transgenic plants are tolerant of heavy metal ions, e.g., cadmium, arsenate and/or mercury, and can accumulate those ions from a contaminated environment, to thus, effect phytoremediation of a contaminated soil or water environment which contains mercury, cadmium and/or arsenate ions.