Phytoremediation of cadmium contamination: overexpression of metallotionein in transgenic tobacco plants

Abstract

The contamination of heavy metals by mining and combustion of fossil fuel has brought about significant deleterious consequences not only to environment but also to human health. Cadmium is a potentially toxic metal which causes renal dysfunction, pulmonary emphysema, and possibly bone demineralization. To explore the potential of plants to tolerate this metal, we engineered a model plant, Nicotiana tabacum, to express a metallothionein under the control of CaMV 35S promoter. Transgenic plants expressing metallothionein were able to grow in concentrations of up to 200 μM CdSO4. Nontransgenic plants promptly underwent leaf chlorosis and their growth and development were inhibited on the medium containing 50 μM CdSO4. PCR analysis for CdSO4 from sensitive and resistant T2 seedlings confirmed a high correlation between increased Cd-tolerance and the transgenic genotype, indicating that cadmiun resistance is stably inherited in the next generation. This result suggests one possible strategy for phytoremediation of heavy metals by expression of plant MT.