Selection and characterization of cadmium-resistant suspension cultures of the wild tomato Lycopersicon peruvianum.

Suspension cultures of Lycopersicon peruvianum were selected for resistance to cadmium by stepwise exposure to increasing concentrations of cadmium sulfate. Resistant cells grow in 1500 micromolar Cd(++). This resistance was retained for thirty generations without selection. Both resistant and parental sensitive cultures take up Cd(++) at similar rates and to the same final levels. Exposure of sensitive or resistant cultures to Cd(++), Cu(++), or Zn(++) leads to the intracellular accumulation of a low molecular weight, cysteine-rich, cadmium-binding protein. This metallothionein is induced over fifteen fold by 100 μM cadmium and builds up to about five fold higher levels in the resistant cultures.