Figure 1.

ApB73 is an important virulence factor of Ustilago maydis. (a) apB73 is up‐regulated during biotrophic growth stages. Transcript levels of apB73 were measured at different growth stages of FB1/FB2 by quantitative real‐time polymerase chain reaction (qPCR). For normalization, the constitutive gene peptidyl‐prolyl isomerase (ppi) was used. We analysed three biological replicates; error bars indicate standard deviation. (b) ApB73 is essential for the virulence of U. maydis in maize cv. B73. Disease rating of maize seedlings at 12 days post‐infection (dpi) with the progenitor strain SG200, the SG200ΔapB73 deletion strain or the complementation strain SG200ΔapB73‐apB73‐HA. In the top row, photographs of the respective strain are shown after growth on filamentation‐inducing charcoal plates for 24 h. Disease scores are shown on the right. The mean values of three independent infections are depicted and the total number of infected plants is indicated above the respective columns. The mean and standard deviation of relative counts from replicates are displayed. For clarity, only positive error bars are shown. P values were calculated by Fisher's exact test. Multiple testing correction was performed using the Benjamini–Hochberg procedure. ****P < 0.0001. (c) Microscopic analysis of the ApB73 virulence phenotype. Maize plants of cv. B73 were infected with the progenitor strain SG200, the SG200ΔapB73 deletion strain or the complementation strain SG200ΔapB73‐apB73‐HA, and harvested at 2 or 7 dpi. Photographs were taken after staining the leaf tissue with WGA‐AlexaFluor488 (green) to visualize fungal chitin and propidium iodide (red) to observe plant cell walls. Bar, 100 µm.