Genotoxic effect of cadmium is associated with apoptotic changes in tobacco cells
This work explores the influence of cadmium on a suspension cell culture of Nicotiana tabacum (TBY-2) by examining cell morphology, viability and DNA integrity. Changes in these parameters were strikingly dependent on concentration of cadmium in the culture medium: a concentration of 50-100 mmol m(-3) CdSO4 induced apoptotic changes including DNA fragmentation into oligonucleosomal units, while 1 mol m(-3) Cd2+ showed strong cytotoxicity, but no fragmentation of DNA, Low cadmium concentrations (below 10 mmol m(-3)) affected neither cell viability nor DNA integrity. A detailed kinetic study showed a significant delay in the onset of apoptosis after the application of high concentrations of cadmium. From days 0-3 after the application of 50 mmol m(-3) CdSO4, the morphology of the cells, their viability and growth were indistinguishable between control and treated cells, and 'domain' DNA fragmentation into 50-200 kb fragments was observed at the DNA level. After this (days 4-7), there was a characteristic and rapid decrease in cell viability, distinct changes in cell. morphology and oligonucleosomal fragmentation. The results suggest that chronic exposure of plant cells to cadmium can trigger programmed cell death.