ABSTRACTEffector proteins are secreted by plant pathogens to enable host colonization. Typically, effector genes are tightly regulated, have very low expression levels in axenic conditions, and are strongly induced during host colonization. Chromatin remodeling contributes to the activation of effector genesin plantaby still poorly known mechanisms. In this work we investigated the role of histone acetylation in effector gene derepression in plant pathogens. We usedZymoseptoria tritici, a major pathogen of wheat, as a model to determine the role of lysine acetyltransferases (KATs) in plant infection. We showed that effector gene activation is associated with chromatin remodeling, featuring increased acetylation levels of histone H3 lysine 9 (H3K9) and 14 (H3K14) in effector loci. We functionally characterized the role ofZ. triticiKATs and demonstrated their distinct contributions to growth, development, and infection. Sas3 is required for host colonization and pycnidia production, while Gcn5 has a major role in pycnidia production. Furthermore, we demonstrated that Sas3 is involved in acetylation of H3K9 and H3K14 in effector loci and in effector gene activation during plant infection. We propose that Sas3-mediated histone acetylation is required for spatiotemporal activation of effector genes and virulence ofZ. tritici.IMPORTANCEPathogen infections require the production of effectors that enable host colonization. Effectors have diverse functions and are only expressed at certain stages of the infection cycle. Thus, effector genes are tightly regulated by several mechanisms, including chromatin remodeling. Here, we investigate the role of histone acetylation in effector gene activation in the fungal wheat pathogenZymoseptoria tritici. We demonstrated that lysine acetyltransferases (KATs) are essential for the spatiotemporal regulation of effector genes. We show that two KATs, Sas3 and Gcn5, are involved in leaf symptom development and pycnidia formation. Importantly, our results indicated that Sas3 controls histone acetylation of effector loci and is a regulator of effector gene activation during stomatal penetration. Overall, our work demonstrates the key role of histone acetylation in regulating gene expression associated with plant infection.