Histone modification dynamics at H3K27 in Pyricularia (Magnaporthe) oryzae

Fungal plant pathogens use a diverse set of secreted proteins and small molecules, termed effectors, to suppress host immunity and promote colonization. Effectors are highly expressed in planta but remain transcriptionally repressed ex planta. Mechanistic understanding of this transcriptional regulation remains limited. Based on previous observations, we hypothesized that repressive histone modification at H3-Lys27 underlies effector transcriptional silencing ex planta, and that exchange for an active chemical modification contributes to in planta transcription. We tested two related hypotheses: that H3K27me3 is involved in suppressing effectors and other in planta induced genes during in vitro growth, and dynamic change between trimethylation and acetylation at H3K27 underlies the switch between a repressed and activated state. Using a combination of fungal molecular genetics, epigenomics, and transcriptomics analysis, we demonstrate that histone modification dynamics at H3K27 can regulate specific genomic loci, often important during host infection, supporting the hypothesis.