Department of Genetics, Karlsruhe Institute of Technology, 76187 Karlsruhe, Germany.
Plant Cell. 2010 Aug;22(8):2908-22. doi: 10.1105/tpc.110.076265. Epub 2010 Aug 20.
Regulation of the cell cycle and morphogenetic switching during pathogenic and sexual development in Ustilago maydis is orchestrated by a concerted action of the a and b mating-type loci. Activation of either mating-type locus triggers the G2 cell cycle arrest that is a prerequisite for the formation of the infectious dikaryon; this cell cycle arrest is released only after penetration of the host plant. Here, we show that bW, one of the two homeodomain transcription factors encoded by the b mating-type locus, and the zinc-finger transcription factor Rbf1, a master regulator for pathogenic development, interact with Clp1 (clampless 1), a protein required for the distribution of nuclei during cell division of the dikaryon. In addition, we identify Cib1, a previously undiscovered bZIP transcription factor required for pathogenic development, as a Clp1-interacting protein. Clp1 interaction with bW blocks b-dependent functions, such as the b-dependent G2 cell cycle arrest and dimorphic switching. The interaction of Clp1 with Rbf1 results in the repression of the a-dependent pheromone pathway, conjugation tube formation, and the a-induced G2 cell cycle arrest. The concerted interaction of Clp1 with Rbf1 and bW coordinates a- and b-dependent cell cycle control and ensures cell cycle release and progression at the onset of biotrophic development.
玉米黑粉菌中致病性和有性发育过程中的细胞周期调控和形态发生转换是由 a 和 b 交配型基因座的协同作用协调的。激活任一交配型基因座都会触发 G2 细胞周期停滞，这是形成传染性双核体的先决条件；只有在穿透宿主植物后，这种细胞周期停滞才会被释放。在这里，我们表明，b 交配型基因座编码的两个同源域转录因子之一 bW 和锌指转录因子 Rbf1（致病性发育的主要调节剂）与 Clp1（无蹼 1）相互作用，Clp1 是双核体细胞分裂过程中核分布所必需的蛋白质。此外，我们还鉴定出 Cib1，一种以前未发现的、对致病性发育至关重要的 bZIP 转录因子，为 Clp1 的互作蛋白。Clp1 与 bW 的相互作用阻止了 b 依赖性的功能，如 b 依赖性的 G2 细胞周期停滞和二态性转换。Clp1 与 Rbf1 的相互作用导致 a 依赖性的信息素途径、交配管形成和 a 诱导的 G2 细胞周期停滞受到抑制。Clp1 与 Rbf1 和 bW 的协同相互作用协调了 a 和 b 依赖性的细胞周期控制，并确保了生物营养发育开始时的细胞周期释放和进展。
