Septation of Infectious Hyphae Is Critical for Appressoria Formation and Virulence in the Smut Fungus Ustilago Maydis

PLoS Pathogens

Michael Bölker¹  Johannes Freitag²  Kay Oliver Schink²  Christian Böhmer²  Björn Sandrock²  Daniel Lanver³ 

[1] Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo, Norway;Department of Biology, Philipps-University Marburg, Marburg, Germany;Max-Planck-Institute for Terrestrial Microbiology, Department of Organismic Interactions, Marburg, Germany

关键词: Appressoria;    Ustilago maydis;    Fungal structure;    Septins;    Cell cycle;    cell division;    Mitosis;    Guanosine triphosphatase;    Leaves;   

DOI  :  10.1371/journal.ppat.1002044

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Differentiation of hyphae into specialized infection structures, known as appressoria, is a common feature of plant pathogenic fungi that penetrate the plant cuticle. Appressorium formation in U. maydis is triggered by environmental signals but the molecular mechanism of this hyphal differentiation is largely unknown. Infectious hyphae grow on the leaf surface by inserting regularly spaced retraction septa at the distal end of the tip cell leaving empty sections of collapsed hyphae behind. Here we show that formation of retraction septa is critical for appressorium formation and virulence in U. maydis. We demonstrate that the diaphanous-related formin Drf1 is necessary for actomyosin ring formation during septation of infectious hyphae. Drf1 acts as an effector of a Cdc42 GTPase signaling module, which also consists of the Cdc42-specific guanine nucleotide exchange factor Don1 and the Ste20-like kinase Don3. Deletion of drf1, don1 or don3 abolished formation of retraction septa resulting in reduced virulence. Appressorium formation in these mutants was not completely blocked but infection structures were found only at the tip of short filaments indicating that retraction septa are necessary for appressorium formation in extended infectious hyphae. In addition, appressoria of drf1 mutants penetrated the plant tissue less frequently.

【 授权许可】

CC BY