Mycophenolic Acid as a Promising Fungal Dimorphism Inhibitor to Control Sugar Cane Disease Caused by Sporisorium scitamineum

The morphological changes from single-cell yeast to filamentous hypha form are critical in plant pathogenic smut fungi. This dimorphic switch is tightly regulated by complex gene pathways in pathogenic development. The phytopathogenic basidiomycetes Sporisorium scitamineum displays a morphological transition from budding growth of haploid cells to filamentous growth of the dikaryon, which enables fungi to forage for nutrients and evade the host plant immune system. In the search for compounds that affect dimorphic switch instead of killing the cell directly, a natural product, mycophenolic acid (MPA), was purified and exhibited significant dimorphism inhibitory activities with minimum effective concentrations of 0.3 mu g/mL. RNA sequencing and real-time quantitative transcription-PCR analysis showed that treatment of 100 mu g/mL MPA dramatically repressed the expression of the ammonium transporter gene Ssa2. A further subcellular localization experiment, ammonium response assay, and Western blot assay confirmed that Ssa2 could be one of the most important molecular targets of MPA in regulating dimorphism of S. scitamineum. These observations suggest that Ssa2 serves as a molecular target of MPA and could be used in the treatment of sugar cane smut diseases caused by S. scitamineum.