UvPomt, an O-Methyltransferase Interacting with UvMAT1-1-3, for Regulating Growth, Stress Tolerance, and Virulence in Ustilaginoidea virens.

Rice false smut (RFS), caused by Ustilaginoidea virens (teleomorph: Villosiclava virens), is a devastating fungal disease that severely impacts global rice production by reducing both yield and grain quality. While the mating-type gene UvMAT1-1-3 is known to regulate both sexual and asexual reproduction in U. virens, its regulatory mechanism remains unclear. In this study, an interacting protein of UvMAT1-1-3, a putative O-methyltransferase (UvPomt), was identified using yeast two-hybrid screening, and its interaction was further confirmed by co-localization microscopy. A quantitative reverse transcription PCR (qRT-PCR) analysis showed a significant up-regulation of UvPomt expression during the early infection stage of U. virens. Functional characterization revealed that ΔUvPomt mutants exhibited reduced fungal pathogenicity, vegetative growth, conidial production, and stress adaptation. Furthermore, a Western blot analysis revealed that the UvMAT1-1-3 protein level was reduced in ΔUvPomt mutants, whereas the UvPomt protein level was elevated in ΔUvMAT1-1-3 mutants. Taken together, these findings suggest a potential reciprocal regulation between UvPomt and UvMAT1-1-3. Understanding UvPomt's function could provide a potential molecular target for controlling RFS disease.