Accumulation of cadmium by transgenic tobacco

Especially tailored transgenic plants were prepared for the purpose of phytoremediation. In the case of heavy metals, high accumulation in plants is the main requirement, particularly in the harvestable parts. Improvement in a plant's ability to tolerate heavy metals via the introduction of metallothionein (MT) genes has already been demonstrated by different authors. In this study, an additional metal binding domain to the implemented protein was introduced in order to further enhance the metal binding capacity. For this reason, gene coding a peptide containing six histidine moieties was combined with a CUP1 yeast metallothionein gene originating from Saccharomyces cerevisiae, which was introduced into tobacco plants using an Agrobacterium tumefaciens vector. Transformants selected on the basis of the kanamycine resistance were checked for the presence of transgenes by RNA isolation of aseptic plants and RT-PCR. The effectiveness of the obtained lines of genetically modified tobacco plants to accumulate heavy metals was tested on sand media with the addition of KNOP's nutrient solution modified by the addition of cadmium (0.2 mg Cd/l as Cd (NO3)(2) x 4 H2O), and compared with non-transformed control plants (the average of the controls was 16.9 mg Cd/kg of dry matter (DM) above ground and 14.3 mg Cd/kg DM in roots). The best performing line HisCUP-X accumulated 90% more Cd in above-ground parts (31.3 mg Cd/kg DM above ground, 10.6 mg Cd/kg DM in roots) during the six-week test period without visible differences in the growth characteristics. Increased translocation into the harvestable parts of the plant is considered as especially important.