Cadmium tolerance and accumulation in transgenic tobacco plants with a yeast metallothionein combined with a polyhistidine tail

Cadmium accumulation and tolerance were tested using tobacco, Nicotiana tabacum L. var. Wisconsin 38 as the control (WSC) and a genetically modified line of the same variety bearing the transgene coding for the polyhistidine cluster, combined with yeast metallothionein (HisCUP). The screening test was conducted on sand nutrient medium with the addition of Knop's nutrient solution, modified by addition of various quantities of cadmium. Relative to the control, there were significant increases in cadmium accumulation in the aerial parts of HisCUP tobacco growing in cadmium concentrations of 0.2 and 0.6 mg cadmium l −1 nutrient solution. Addition of 5.4 mg cadmium l −1 induced symptoms of cadmium toxicity in the control tobacco, and the highest dose of cadmium was lethal. HisCUP showed increasing resistance to the stress response induced by cadmium. Experiments were continued in pots with two differently polluted soils. The cadmium content in the aerial biomass of transgenic tobacco increased by 45–75% compared with the control.