Duel function of Fly1 in Ustilago maydis-maize pathosystem
B. ÖKMEN (1), B. Kemerich (2), D. Hilbig (2), J. Aschenbroich (3), K. Schipper (3), G. Doehlemann (2) (1) University of Cologne, Germany; (2) University of Cologne, Germany; (3) Heinrich-Heine University, Germany

Chitinases are widely distributed across diverse biological systems. While fungal chitinases are responsible for cell-wall remodeling during growth and morphogenesis, plant chitinases are strongly induced upon pathogen attack and establish an important arsenal of plants against different pathogens. As a counter attack, fungal pathogens have evolved strategies to evade or suppress the antifungal activity of plant chitinases. The dimorphic basidiomycete Ustilago maydis is causal agent of maize smut disease; however, it is unknown how this biotroph deals with plant chitinases. By using yeast-two-hybrid, we found that an U. maydis metalloprotease (Fly1) interacts with maize ZmChitA. The fly1 deletion mutants U. maydis showed drastically reduced virulence compared to the wild-type, demonstrating virulence function of Fly1. While fly1 mutants are not affected in growth, filamentation and pathogenic differentiation, they show a cytokinesis defect in yeast stage, leading to formation of aggregates in liquid culture. Since their in vitro phenotype perfectly resembled a U. maydis chitinase double mutant (cts1/cts2) (Langner et al., 2015), chitinase activity was tested for both wild-type and umfly1 deletion mutants. Surprisingly, Cts1 (fungal chitinase) activity was significantly reduced in fly1 deletion mutants compared to wild-type, while there was no significant difference in expression level of any fungal chitinase genes. Based on our results, we propose that Fly1 is required for activation of endogenous Cts1 in yeast stage. Moreover, we hypothesize that Fly1 has a duel function to disarm plant chitinase, reflecting adaptation of U. maydis to its pathogenic lifestyle.

Abstract Number: P6-147
Session Type: Poster