Haplo-insufficiency for different genes differentially reduces pathogenicity and virulence in a fungal phytopathogen

► Ustilago maydis is a fungal pathogen of maize. ► Five genes were identified in this fungus that display haplo-insufficiency. ► All encoded signaling components (homologs of Ste20, Hsl7, 14-3-3, Rho1, Pde1). ► Single allele deletions in diploids altered mating, and/or pathogenicity. ► For all but Pde1, the effects seem due to stoichiometric imbalances in complexes.