Genetic and Molecular Dissection of Hyphal Anastomosis

丝状真菌是环境中植物纤维物质的主要降解者。不同种类的丝状真菌与几乎所有植物物种的根都以共生关系联系在一起，使植物能够从土壤中获得微量营养素。此外，其他物种是植物中的致病因子，或引起重要的人类疾病。所有这些丝状真菌，无论是有益的还是致病的，都通过顶端延伸、分枝和菌丝融合生长形成菌丝网络。菌丝网络的形成对于根伴生真菌和腐生真菌在整个生态系统中的营养转移以及病原真菌中菌落的建立和资源的开发是至关重要的。虽然丝状真菌的顶端生长和分枝已经得到了广泛的研究，但对菌丝融合的机制或菌丝网络的功能知之甚少。丝状真菌粗脉孢子菌菌丝融合的活体细胞成像和遗传分析表明，菌丝融合过程是一个复杂的、受严格调控的生物学过程。目前已鉴定出大量菌丝融合所必需的成分，包括信号转导途径成分、极化成分、丝状真菌特异性蛋白和跨膜蛋白等。菌丝融合突变体除了生长速度较慢和/或达到最大生长速度的滞后期外，还表现出发育缺陷。这些观察表明，丝状真菌中相互连接的网络的形成对于开发环境生态位和发育过程都是必不可少的。本研究的目的是结合活细胞成像、遗传分析和生化工具，剖析菌丝萌发/菌丝融合的过程，以阐明自我信号、极化和膜合并的机制，最终目的是了解菌丝网络在生态系统、共生和致病中的作用。更广泛的影响：丝状真菌中的菌丝融合可与其他生物中遗传相同的细胞之间的细胞融合事件相媲美，例如导致合胞体的细胞-细胞融合，例如肌肉分化期间的成肌细胞融合，胎盘发育期间的滋养细胞融合，以及骨形成期间破骨细胞之间的融合。因此，研究粗毛藻中的细胞-细胞融合为理解更复杂的真核生物中细胞融合事件的分子机制提供了有用的模型。该项目为本科生、研究生和博士后助理提供了优秀的培训项目。许多本科生加州机会学者被招募到这个项目中；这些学生来自湾区的弱势背景和表现不佳的学校。

Intellectual Merit Filamentous fungi are the primary degraders of plant cellulosic material in the environment. Different species of filamentous fungi are associated with the roots of almost all plant species in a symbiotic relationship that allows plants to gain micronutrients from soil. In addition, other species are disease causing agents in plants, or cause important human diseases. All of these filamentous fungi, both beneficial and pathogenic species, grow by tip extension, branching and hyphal fusion to form a hyphal network. The formation of the hyphal network is believed to be essential for transfer of nutrients throughout ecosystems by root associated and saprophytic fungi and for colony establishment and exploitation of resources in pathogenic fungi. Although tip growth and branching have been extensively studied in filamentous fungi, little is known about the mechanism of hyphal fusion or the function of the hyphal network. Live cell imaging and genetic analysis of hyphal fusion in the model filamentous fungus, Neurospora crassa have revealed that the process of hyphal fusion is a complex and carefully regulated biological process. A large number of components essential for hyphal fusion have been identified in N. crassa, including components of signal transduction pathways, polarization components, filamentous fungal specific proteins and transmembrane proteins. Hyphal fusion mutants show developmental defects, in addition to slower growth rates and/or lag phase to reach maximal growth rate. These observations indicate that the formation of an interconnected network in filamentous fungi is essential for both exploitation of an environmental niche and for developmental processes. The objectives of this research are to dissect the process of germling/hyphal fusion using a combination of live cell imaging, genetic analysis and biochemical tools to elucidate the mechanisms of self-signaling, polarization and membrane merger with the ultimate goal of understanding the role of hyphal networks in ecosystems, symbiosis and pathogenesis. Broader Impact:Hyphal fusion in filamentous fungi is comparable to cell fusion events between genetically identical cells in other organisms, such as cell-cell fusion resulting in syncytia, such as myoblast fusion during muscle differentiation, trophoblast fusion during placental development and between osteoclasts during bone formation. Thus, studying cell-cell fusion in N. crassa provides a useful model for understanding molecular mechanisms of cell fusion events in more complex eukaryotic species. This project provides excellent training projects for undergraduate, graduate students and post-doctoral associates. A number of undergraduate California Opportunity Scholars have been recruited to this project; these students come from disadvantaged backgrounds and low performing schools in the Bay Area.