High peroxidase activity and stable changes in the cell wall are related to dichlobenil tolerance

Suspension-cultured bean cells habituated to growth in a lethal concentration of dichlobenil were cultured for 3-5 years in a medium lacking the inhibitor in order to obtain long-term dehabituated cell lines. The growth parameters, cell morphology and ultrastructure of cells in the absence of dichlobenil reverted to that of non-habituated cells. The cellulose content and Fourier transform infrared (FTIR) spectra of crude cell walls from long-term dehabituated cells were also similar to those of non-habituated cells. However, long-term dehabituated cells showed three times more tolerance to dichlobenil than non-habituated cells. The incorporation of [(14)C]Glc into cellulose was reduced by 40% in dehabituated cells when compared with non-habituated cells. However, the addition of dichlobenil to dehabituated cells increased the incorporation of [(14)C]Glc into cellulose 3.3-fold with respect to that of non-habituated cells. Dehabituated cells showed a constitutively increased peroxidase activity when compared with non-habituated cells. Results reported here indicate that the habituation of bean cultured cells to dichlobenil relied partially on a stable change in the cellulose biosynthesis complex and is associated with high guaiacol peroxidase activity.