The plant cell/microbe coincubation assay for the analysis of plant-activated promutagens.

The preincubation and suspension procedures of the plant cell/microbe coincubation assay are described and the activation of 2-aminofluorene and m-phenylenediamine by cultured tobacco, cotton, carrot and maize cells is compared. The assay measures the plant activation of promutagens into genotoxins detected in Salmonella typhimurium as well as toxicity in plant and microbial cells. At concentrations of 2-aminofluorene 0-0.5 mumoles/reaction tube, the rank order of the efficiency of activation by plant cells was tobacco much greater than cotton greater than carrot. Cultured maize cells did not activate 2-aminofluorene. The tobacco cell activation of 2-aminofluorene was inhibited 50% by 750 microM diethyldithiocarbamate under conditions that did not affect the cell viability. Tobacco cells were also the most efficient plant cells in activating m-phenylenediamine (0-5 mumoles/reaction tube). The 'biological affinity' of m-phenylenediamine for the activation system in tobacco cells was approximately 100 microM.