Molecular and Genetic Dissection of Hyphal Anastomosis

丝状真菌通过尖端延伸、分枝和菌丝融合生长，形成菌丝网络，构成真菌个体。尽管对丝状真菌的尖端生长和分支进行了广泛的研究，但对菌丝融合的机制和菌丝网络形成的功能基本上一无所知。本实验室利用活细胞成像和共聚焦显微镜对丝状真菌神经孢子菌（Neurospora crassa）菌丝融合过程进行了研究，揭示了一个复杂而精心调节的生物过程，对真菌个体有明显的影响。菌丝融合是增加菌丝细胞质流动和相互联系的一种方式，这可能在菌丝内交流中起重要作用，影响菌丝模式的形成和发育过程。丝状真菌中的菌丝融合与其他生物中的细胞融合事件类似，如卵子和精子之间的受精事件，以及导致合胞体的体细胞融合事件，如肌肉分化过程中的成肌细胞融合。菌丝融合过程必须仔细调节，因为不适当的细胞壁破坏会导致菌丝裂解。由于其易于使用活细胞成像技术（http://www.neurospora.com/）、全基因组序列信息（http://www-genome.wi.mit.edu/annotation/fungi/neurospora/）、菌丝融合突变体的可用性以及易于使用遗传和分子技术，crassa是评估丝状真菌菌丝融合过程和功能的最佳丝状真菌。初步结果表明，菌丝融合需要一系列信号事件，其中一个是由map激酶途径介导的。菌丝融合突变体表现出生理和发育缺陷，表明不能形成菌丝网络具有生理后果。本项目的目的是利用共聚焦显微镜下的活细胞成像、遗传和生化分析相结合的方法来表征菌丝融合突变体，以阐明自信号传导、极化和膜融合的机制。最终目标是了解菌丝网络的形成如何使真菌个体能够完成其生命周期所需的生理和发育过程。了解丝状真菌菌丝融合过程不仅可以揭示菌丝网络形成的功能，而且可以为其他真核生物的细胞融合事件提供模型。

Filamentous fungi grow by tip extension, branching and hyphal fusion to form a hyphal network that makes up a fungal individual. Although tip growth and branching have been extensively studied in filamentous fungi, essentially nothing is known about the mechanism of hyphal fusion or the function of the formation of a hyphal network. Studies by this laboratory on the hyphal fusion process using live cell imaging and confocal microscopy in the filamentous fungus, Neurospora crassa, have revealed a complex and carefully regulated biological process with obvious consequences to the fungal individual. Hyphal fusion is a way to increase cytoplasmic flow and interconnectedness of hyphae, which may be important in intra-hyphal communication that influences hyphal pattern formation and developmental processes. Hyphal fusion in filamentous fungi is comparable to cell fusion events in other organisms, such as fertilization events between egg and sperm and somatic cell fusion events that result in syncytia, such as myoblast fusion during muscle differentiation. The hyphal fusion process must be carefully regulated because inappropriate cell wall breakdown would result in lysis of the hyphae. N. crassa is the best filamentous fungus to assess the process and function of hyphal fusion in filamentous fungi because of its tractability for live cell imaging techniques (http://www.neurospora.com/), full genome sequence information (http://www-genome.wi.mit.edu/annotation/fungi/neurospora/), the availability of hyphal fusion mutants, and the ease of genetic and molecular techniques. Preliminary results indicate that a series of signaling events are required for hyphal fusion, one of which is mediated by a map kinase pathway. Hyphal fusion mutants show physiological and developmental defects, suggesting that the failure to form a hyphal network has physiological consequences. The objectives of this project are to characterize hyphal fusion mutants using a combination of live cell imaging via confocal microscopy, and genetic and biochemical analysis to elucidate the mechanism of self-signaling, polarization and membrane fusion. The ultimate goal is to understand how the formation of the hyphal network allows a fungal individual to perform the physiological and developmental processes required to complete its life cycle. Understanding the hyphal fusion process in filamentous fungi will not only reveal the function of the formation of the hyphal network, but will provide a model for cell fusion events in other eukaryotic organisms.