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Regulation of cell separation in the dimorphic fungus Ustilago maydis
Author(s) -
Weinzierl Gerhard,
Leveleki Leonora,
Hassel Annette,
Kost Gerhard,
Wanner Gerhard,
Bölker Michael
Publication year - 2002
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2002.03010.x
Subject(s) - ustilago , biology , cytokinesis , guanine nucleotide exchange factor , microbiology and biotechnology , cdc42 , mutant , gtpase , cell division , genetics , cell , gene
Summary During its haploid phase the dimorphic fungus Ustilago maydis grows vegetatively by budding. We have identified two genes, don1 and don3 , which control the separation of mother and daughter cells. Mutant cells form tree‐like clusters in liquid culture and grow as ring‐like ( don ut‐shaped) colonies on solid medium. In wild‐type U. maydis cells, two distinct septa are formed during cytokinesis and delimit a fragmentation zone. Cells defective for either don1 or don3 display only a single septum and fail to complete cell separation. don1 encodes a guanine nucleotide exchange factor (GEF) of the Dbl family specific for Rho/Rac GTPases. Don3 belongs to the germinal‐centre‐kinase (GC) subfamily of Ste20‐like protein kinases. We have isolated the U. maydis homologues of the small GTP binding proteins Rho2, Rho3, Rac1 and Cdc42. Out of these, only Cdc42 interacts specifically with Don1 and Don3 in the yeast two‐hybrid system. We propose that Don1 and Don3 regulate the initiation of the secondary septum, which is required for proper cell separation.