Chromatin dynamics contribute to the spatio-temporal expression pattern of virulence genes in a fungal plant pathogen

The fungus Zymoseptoria tritici is the main pathogen of wheat in Europe. It is a filamentous fungus that causes septoria tritici blotch and produces necrosis in wheat leaves after an asymptomatic phase. In the recently published work in mBio led by Dr. Andrea Sánchez-Vallet, principal investigator of the group "Molecular mechanisms of virulence of fungal wheat pathogens", several virulence genes of Z. tritici were shown to be induced during penetration through the stomata and in the apoplast. However, earlier during infection when the hyphae grow on the leaf surface or in the absence of the host, the virulence genes are not expressed. This typical expression pattern was shown to be mediated by chormatin modifications, featuring a reduction in trimethylated lysine 27 of histone H3 (H3K27me3). The work demonstrates that chromatin modifications triggered during host colonization determine the specific expression profile of effector genes at the cellular level and, hence, provide new insights into the regulation of virulence in fungal plant pathogens.