Role of the histone acetyltransferase Rtt109 in development and pathogenicity of the rice blast fungus

Abstract

Acetylation of histone H3 lysine 56 (H3K56) by the fungalspecific histone acetyltransferase Rtt109 plays important rolesin maintaining genome integrity and surviving DNA damage.Here, we investigated the implications of Rtt109-mediated response to DNA damage on development and pathogenesis of therice blast fungus Magnaporthe oryzae (anamorph: Pyriculariaoryzae). The ortholog of Rtt109 in M. oryzae (MoRtt109) wasfound via sequence homology and its functionality was confirmed by phenotypic complementation of the Saccharomycescerevisiae Rtt109 deletion strain. Targeted deletion of MoRtt109resulted in a significant reduction in acetylation of H3K56 andrendered the fungus defective in hyphal growth and asexualreproduction. Furthermore, the deletion mutant displayedhypersensitivity to genotoxic agents, confirming the conservedimportance of Rtt109 in genome integrity maintenance andgenotoxic stress tolerance. Elevated expression of DNA repairgenes and the results of the comet assay were consistent withconstitutive endogenous DNA damage. Although the conidiaproduced from the mutant were not impaired in germinationand appressorium morphogenesis, the mutant was significantlyless pathogenic on rice leaves. Transcriptomic analysis provided insight into the factors underlying phenotypic defectsthat are associated with deficiency of H3K56 acetylation.Overall, our results indicate that MoRtt109 is a conservedhistone acetyltransferase that affects proliferation and asexualfecundity of M. oryzae through maintenance of genome integrity and response to DNA damage.