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 <i>Ustilaginoidea virens</i> (teleomorph: <i>Villosiclava virens</i>), is a devastating fungal disease that severely impacts global rice production by reducing both yield and grain quality. While the mating-type gene <i>UvMAT1-1-3</i> is known to regulate both sexual and asexual reproduction in <i>U. virens,</i> 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 <i>UvPomt</i> expression during the early infection stage of <i>U. virens</i>. Functional characterization revealed that Δ<i>UvPomt</i> 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 Δ<i>UvPomt</i> mutants, whereas the UvPomt protein level was elevated in Δ<i>UvMAT1-1-3</i> mutants. Taken together, these findings suggest a potential reciprocal regulation between UvPomt and UvMAT1-1-3. Understanding <i>UvPomt</i>'s function could provide a potential molecular target for controlling RFS disease.