FIG. 4.

GFP-PMK1 was expressed in infectious hyphae. Conidia from strain Xh14 were inoculated on onion epidermal cells and examined under differential interference contrast (left panels) or epifluorescence microscopy (right panels). At 24 h, the majority of appressoria formed by Xh14 had not penetrated plant cells yet and contained strong GFP fluorescence. At 48 h, appressoria of Xh14 that had successfully penetrated onion epidermal cells contained no GFP signal or weak GFP signal. Fluorescence was observed in infectious hyphae without any special cellular localization pattern. In some appressoria, fluorescent signals in underlying infectious hyphae could be observed through the collapsed appressoria. Bar = 10 μm. A, appressorium; IF, infectious hypha; C, conidium.