Weinzierl Gerhard, Leveleki Leonora, Hassel Annette, Kost Gerhard, Wanner Gerhard, Bölker Michael
Institut für Genetik der Universität München, Munich, Germany.
Mol Microbiol. 2002 Jul;45(1):219-31. doi: 10.1046/j.1365-2958.2002.03010.x.
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 (donut-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.
在其二倍体阶段，双态真菌玉米黑粉菌通过出芽进行营养生长。我们鉴定出了两个基因don1和don3，它们控制母细胞和子细胞的分离。突变细胞在液体培养中形成树状簇，并在固体培养基上以环状（甜甜圈状）菌落生长。在野生型玉米黑粉菌细胞中，细胞分裂期间会形成两个不同的隔膜，并界定一个破碎区域。don1或don3有缺陷的细胞仅显示一个隔膜，无法完成细胞分离。don1编码一种对Rho/Rac GTP酶特异的Dbl家族鸟嘌呤核苷酸交换因子（GEF）。Don3属于Ste20样蛋白激酶的生发中心激酶（GC）亚家族。我们分离出了小GTP结合蛋白Rho2、Rho3、Rac1和Cdc42的玉米黑粉菌同源物。其中，只有Cdc42在酵母双杂交系统中与Don1和Don3特异性相互作用。我们提出，Don1和Don3调节次级隔膜的形成，而次级隔膜是正确细胞分离所必需的。
