A small <i>Ustilago maydis</i> effector acts as a novel adhesin for hyphal aggregation in plant tumors

The biotrophic basidiomycete fungus Ustilago maydis causes smut disease in maize. Hallmarks of the are characteristic large tumors which dark pigmented spores formed. Here, we functionally characterized a novel core effector lep1 (late protein 1) is highly expressed during tumor formation and contributes to virulence. We characterize mutants, localize protein, determine phenotypic consequences upon deletion as well constitutive expression, analyze relationships with repellent Rep1 hydrophobins. In tumors, mutants show attenuated hyphal aggregation, fail undergo massive late proliferation produce only few spores. Upon cell aggregation induced surface filamentous colonies displays enhanced hydrophobicity. Lep1 bound wall hyphae associates when constitutively hyphae. conclude that acts kind adhesin functions together other surface-active proteins allow diploid for induction morphological changes associated spore formation.