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。它们包围着有性孢子，由许多不同的细胞类型组成，这些细胞类型是从营养菌丝分化而来的。营养菌丝的融合似乎是子实体发育的先决条件。许多对菌丝融合至关重要的基因也参与子实体发育的调控。通过补充子实体突变体的模式真菌大孢囊壳菌，我们能够分离出基因，这是同样重要的两个过程。该项目的重点是保守的发育蛋白PRO11，哺乳动物纹状体蛋白家族的蛋白质同源物。在哺乳动物中，纹状体蛋白已被鉴定为纹状体相互作用磷酸酶和激酶（STRIPAK）复合物的中心支架蛋白。纹状体蛋白是磷酸酶PP2A的调节亚基，并将磷酸酶PP2A连接到生发中心（GC）III家族的激酶和其他保守蛋白。显然，STRIPAK复合物调节参与菌丝融合和子实体发育所需的信号转导途径的靶蛋白的磷酸化和去磷酸化。在第一个资助期间，我们能够证明纹状体蛋白同源物PRO 11与先前鉴定的发育蛋白一起是S.大孢子虫。这包括SmMOB3，一种假定的激酶激活剂，PRO22，一种纹状体相互作用蛋白，和PP2AA，蛋白磷酸酶2A的支架亚基。在哺乳动物中，STRIPAK复合物的细胞功能尚不清楚。与此相反，功能分析，使用敲除突变体与不同的发展缺陷揭示了真菌的STRIPAK复合体菌丝融合和子实体的发展过程中的作用。该建议的目的是这些相互作用伙伴的功能特性，并确定其在菌丝融合和子实体发育过程中的作用。 这将为我们了解不仅在真菌而且在高等真核生物中的细胞融合和多细胞分化的保守机制提供重要的见解。

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.