Effect of the developmental protein PRO11 and its interaction partners on fruiting-body development and hyphal fusion of Sordaria macrospora

子实体是丝状子囊菌形成的最复杂的三维结构。它们包裹着有性孢子，由许多不同的细胞类型组成，这些细胞类型与营养菌丝不同。营养菌丝融合似乎是子实体发育的先决条件。许多菌丝融合所必需的基因也参与了子实体发育的调控。通过补充模式真菌大孢子菌的子实体突变体，我们能够分离出对这两个过程同样重要的基因。这个项目的重点是保守的发育蛋白PRO11，它是哺乳动物纹状体蛋白家族的同源蛋白。在哺乳动物中，纹状体蛋白被鉴定为纹状体相互作用磷酸酶和激酶(STRIPAK)复合体的中央支架蛋白。Striatin蛋白是磷酸酶PP2A的调节亚单位，将磷酸酶PP2A与生发中心(GC)III家族的激酶和其他保守蛋白联系起来。显然，STRIPAK复合体调节目标蛋白的磷酸化和去磷酸化，这些蛋白参与菌丝融合和子实体发育所需的信号转导途径。在第一个资助期，我们能够证明条纹蛋白同源物PRO11与先前确定的发育蛋白一起是大孢子链霉菌STRIPAK复合体的中心成分。这包括SmMOB3，一种可能的激酶激活剂，PRO22，一种条纹相互作用蛋白，以及PP2AA，蛋白磷酸酶2A的支架亚基。在哺乳动物中，STRIPAK复合体的细胞功能尚不清楚。相反，使用具有明显发育缺陷的敲除突变体进行的功能分析揭示了真菌STRIPAK复合体在菌丝融合和子实体发育中的作用。这项建议的目的是确定这些相互作用伙伴的功能特征，并确定它们在菌丝融合和子实体发育过程中的作用。这将为我们理解细胞融合和多细胞分化的保守机制提供重要的见解，不仅在真菌中，而且在高等真核生物中也是如此。

Fruiting bodies are the most complex three-dimensional structures formed by filamentous ascomycetes. They enclose the sexual spores and are composed of many different cell types which are differentiated from vegetative hyphae. Fusion of vegetative hyphae seems to be a prerequisite for fruiting-body development. Many genes which are essential for hyphal fusion are also involved in the regulation of fruiting-body development. By complementing fruiting-body mutants of the model fungus Sordaria macrospora we were able to isolate genes which are equally important for both processes. The focus of this project is the conserved development protein PRO11, a homolog of proteins of the mammalian striatin family. In mammals, striatin proteins have been identified as central scaffolding proteins of the striatin interacting phosphatase and kinase (STRIPAK) complex. Striatin proteins are regulatory subunits of the phosphatase PP2A and link phosphatase PP2A to kinases of the germinal center (GC) III family and additional conserved proteins. Apparently, the STRIPAK complex regulates the phosphorylation and de-phosphorylation of target proteins which are involved in signal transduction pathways required for hyphal fusion and fruiting-body development. During the first funding period we were able to demonstrate that the striatin homolog PRO11 together with previously identified developmental proteins is a central component of a STRIPAK complex in S. macrospora. This includes SmMOB3, a putative kinase activator, PRO22, a striatin interacting protein, and PP2AA, the scaffolding subunit of protein phosphatase 2A. In mammals, the cellular function of the STRIPAK complex is unknown. In contrast, functional analysis using knockout mutants with distinct developmental defects revealed a role of the fungal STRIPAK complex during hyphal fusion and fruiting-body development. The aim of this proposal is the functional characterization of these interaction partners und to define their role during hyphal fusion and fruiting-body development. This will give us crucial insights to understand conserved mechanisms for cell fusion and multicellular differentiation not only in fungi but also in higher eukaryotes.