Effects of the demethylase inhibitor, cyproconazole, on hyphal tip cells of Sclerotium rolfsii. I. A light microscope study

The effects of cyproconazole on hyphal tip cells of Sclerotium rolfsii were examined in living cells using Nomarski optics and in fixed cells using epifluorescence staining. Hyphae grown on cyproconazole were often undulated in appearance, generally smaller in diameter, had shorter septal distances, and exhibited a higher degree of branching than did control cells. Swelling of the tip region and disruption of the spitzenkörper were frequently observed within 10 min after exposure to the fungicide at concentrations of 1.0 μg/ml. Staining with 3,3′-dihexyloxacarbocyanine iodine revealed that fewer organized Spitzenkörper were present in cells grown on agar amended with 0.1 and 0.75 μg/ml fungicide. Staining with calcofluor white, after 60 min exposure to 0.75 μg/ml of cyproconazole, showed that apical wall deposition had decreased and patchy subapical deposition appeared. Immunofluorescence staining of the microtubule cytoskeleton revealed altered patterns in microtubule arrays after 30 min exposure to cyproconazole (0.75 μg/ml). Nuclear staining with DAPI demonstrated that positioning of nuclei within the cell was not altered as a result of the fungicide. Studies using [¹⁴C]cyproconazole indicated that the maximum levels of fungicide in hyphal cells were obtained within 60 min of exposure to 0.75 μg/ml. The amount of fungicide associated with hyphal cells decreased to a constant level by 240 min.