Directional control of extreme polar growth in filamentous fungi

生长发育的一个关键方面是细胞形状的控制。这一点的基础是细胞建立和维持极性的能力，每个细胞具有定义的取向。一个极端的例子是神经元，它能够以线性方式延伸到它们在整个有机体中发挥信号转导作用所需的长距离上。同样，丝状真菌产生线状菌丝，线状菌丝通过分枝延伸，形成网络。真菌细胞和其他真核生物极化形成前沿的过程是高度保守的，因为这种真菌代表了一个很好的模型，可以理解决定极性的基本生物过程。除了为其他细胞提供良好的模式生物外，对真菌的研究本身也很重要。真菌是植物病害和食物变质的主要原因，造成全世界10%-20%的作物产量损失。它们也是重要的临床病原体，导致的死亡人数超过疟疾或结核病。然而，真菌在工业生物技术、食品生产中有很大的好处，因为共生菌可以增加作物产量，并且通过生物质降解和营养循环对我们的生态系统至关重要。菌丝生长是真菌探索和进入寄主组织的方式，在生长过程中可以从菌丝顶端释放分泌酶。因此，了解菌丝生长是如何控制的，对上述所有领域都有潜在的影响。所有真核细胞中的极性都由同一组蛋白质控制，即Rho-GTP酶。这些蛋白质的作用是多种多样的；例如，在神经细胞中，它们在轴突形成期间产生一个前锋，在树突形成期间产生多个前锋。同样的一组蛋白质可以在不同的时间段内协调不同数量的前锋，因为它们嵌入的相互作用网络之间的差异。在这个项目中，我们将观察一个这样的案例，存在于菌丝顶端，以了解这些非常重要的Rho-GTP酶是如何被调节来指导极端极化生长的。当真菌在有利的条件下生长时，它们往往有直的菌丝。已经发现了一组保持直立菌丝形态所必需的蛋白质，称为“细胞末端标记蛋白”。细胞末端标记蛋白和Rho-GTP酶在指导生长方面的功能是重叠的。然而，目前还不知道这两组蛋白质是如何相互作用的，以及细胞末端标记蛋白如何调节Rho-GTP酶以确保持续的单向生长。

A key aspect of growth and development is the control of cell shape. The basis of this is the ability for a cell to establish and maintain polarity, each cell having a defined orientation. An extreme example are neurons, which are able to extend in a linear fashion over the long distances necessary for their role in signal transduction throughout an organism. Similarly filamentous fungi produce linear hyphae, which extend with branching, to form a network. The processes by which fungal cells and other Eukaryotes polarise to form a front are highly conserved, as such fungi represent a good model for understanding the fundamental biological processes that determine polarity. In addition to providing a good model organism for other cells, the study of fungi is important in its own right. Fungi are the major cause of plant disease and food spoilage, being responsible for the loss of 10-20% of crop production worldwide. They are also important clinical pathogens, causing more deaths than either malaria or tuberculosis. However, fungi are of major benefit in industrial biotechnology, food production, as symbionts increasing crop yields and are fundamental to our ecosystem through biomass degradation and nutrient cycling. Hyphal growth is the means by which fungi explore and enter host tissue, and secretory enzymes can be released from hyphal tips during growth. As such understanding how hyphal growth is controlled has potential impact all the areas outlined above. Polarity in all Eukaryotic cells is controlled by the same set of proteins, the Rho-GTPases. The action of these proteins is very versatile; in neuronal cells, for example, they create one front during axon formation, and multiple fronts during dendritic spine formation. The same set of proteins can orchestrate varying numbers of fronts for varying periods of time because of the differences between the interaction networks they are embedded within. In this project we will look at one such case, present at the hyphal tip, to understand how these very important Rho-GTPases are tuned to direct the extreme polarised growth. When fungi are grown in favourable conditions they tend have straight hyphae. A set of proteins has been found that is necessary for the straight hyphal morphology, termed 'cell-end-marker proteins'. The function of the cell-end-marker proteins and the Rho-GTPases, in directing growth, overlap. However, it is not yet known how the two sets of proteins interact and how the cell-end-marker proteins tune the Rho-GTPases to ensure persistent unidirectional growth.