Post-Translational Modification β-Hydroxybutyrylation Regulates Ustilaginoidea virens Virulence

Lysine β-hydroxybutyrylation (K_bhb) is an evolutionarily conserved and widespread post-translational modification that is associated with active gene transcription and cellular proliferation. However, its role in phytopathogenic fungi remains unknown. Here, we characterized K_bhb in the rice false smut fungus Ustilaginoidea virens. We identified 2204 K_bhb sites in 852 proteins, which are involved in diverse biological processes. The mitogen-activated protein kinase UvSlt2 is a K_bhb protein, and a strain harboring a point mutation at K72, the K_bhb site of this protein, had decreased UvSlt2 activity and reduced fungal virulence. Molecular dynamic simulations revealed that K72_bhb increases the hydrophobic solvent-accessible surface area of UvSlt2, thereby affecting its binding to its substrates. The mutation of K298_bhb in the septin UvCdc10 resulted in reduced virulence and altered the subcellular localization of this protein. Moreover, we confirmed that the NAD⁺-dependent histone deacetylases UvSirt2 and UvSirt5 are the major enzymes that remove K_bhb in U. virens. Collectively, our findings identify regulatory elements of the K_bhb pathway and reveal important roles for K_bhb in regulating protein localization and enzymatic activity. These findings provide insight into the regulation of virulence in phytopathogenic fungi via post-translational modifications.