Figure 2
Cytology of infection of barley leaf tissue by the M. oryzae ssd1 mutant. (A) Infection phenotypes of the wild-type Hoku-1 and mossd1 mutant K1. Inoculated leaves at 48 hpi were decolorized and observed with light microscopy. The wild-type strain Hoku-1 formed infection hyphae from appressoria on the plant surface but mossd1 mutant K1 did not show infection hyphae inside plant cell. Ap, appressorium; Ih, infection hypha; Bar = 5 μm. (B) Formation of papilla-like structures under appressoria of ssd1 mutant K1. At 48 hpi, the decolorized leaves were observed with epi-fluorescence microscopy. Autofluorescent papillae were visible beneath appressoria. Ap, appressorium; Pa, papilla; Bar = 5 μm. (C) Frequency of appressorial penetration and host papilla formation. Leaves sprayed with conidial suspension (1 × 106 conidia/ml) were observed at 48 hpi. Infection phenotypes were classified as follows; Ih, infection hyphae under appressoria; Pa, papilla under appressoria; Ap, appressoria without papillae or infection hyphae. Appressoria of the wild-type strain Hoku-1 penetrated with high frequency to form infection hyphae, but those of ssd1 mutant K1 induced papillae with high frequency.