The PP2A phosphatase regulatory subunit SsRts1 regulates morphogenesis, mitosis, sexual mating and virulence in Sporisorium scitamineum

Here, we identified SsRts1 as an interacting protein of SsPpe1, containing a PP2A regulator subunit B56 domain. Deletion of Ssrts1 impaired sporidia growth, morphogenesis, and mitosis. The ΔSsrts1 sporidia exhibited pseudohyphal morphology and abnormal accumulation of autophagic bodies. Meanwhile, the ΔSsrts1 mutants showed increased sensitivity to cell wall, oxidative and hyperosmotic stresses. Additionally, defects in sexual mating, filamentation, and virulence were also observed in the ΔSsrts1 mutants. Global transcriptome analysis revealed that SsRts1 regulates ATPase activity, cell cycle, meiosis, and tryptophan metabolism. Moreover, exogenous tryptophan supplementation partially restored mating and filamentation in the ΔSsrts1 mutants, indicating that SsRts1 modulates these processes partly through the tryptophan catabolism pathway. These findings provide insight into the regulatory roles of PP2A regulatory subunit SsRts1 in S. scitamineum, and enhance our understanding of PP2A function in plant-pathogenic fungi.