The functionally conserved effector Sta1 is a fungal cell wall protein required for virulence in Ustilago maydis

Shigeyuki Tanaka, Isabelle Gollin, Nicole Rössel, Regine Kahmann
2020 New Phytologist  
(1)The biotrophic fungus Ustilago maydis causes the smut disease of maize. The interaction with its host and induction of characteristic tumors are governed largely by secreted effectors whose function is mostly unknown. To identify effectors with a prominent role in virulence, we used RNA-seq and found that the gene sta1 is upregulated during early stages of infection. (2)We characterized Sta1 by comparative genomics, reverse genetics, protein localization, stress assays and microscopy.
more » ... microscopy. (3)sta1 mutants show a dramatic reduction of virulence and show altered colonization of tissue neighboring the vascular bundles. Functional orthologs of Sta1 are found in related smut pathogens infecting monocot and dicot plants. Sta1 is secreted by budding cells but is attached to the cell wall of filamentous hyphae. Upon constitutive expression of Sta1 fungal filaments become susceptible to Congo red, β-glucanase and chitinase, suggesting that Sta1 alters the structure of the fungal cell wall. Constitutive or delayed expression of sta1 during plant colonization negatively impacts on virulence. (4)Our results suggest that Sta1 is a novel kind of effector, which needs to modify the hyphal cell wall to allow hyphae to be accommodated in tissue next to the vascular bundles.
doi:10.1111/nph.16508 pmid:32112567 fatcat:fomiqc3bqncnxbv6mhf4ancefi