Interplay between Self and Non-self recognition mechanisms in Neurospora crassa

随着多细胞的进化，各种挑战也随之而来。极端程度的合作对于多细胞的存在至关重要，需要细胞之间最大限度的协调和沟通。在广泛的生物体中，细胞相互作用的一个关键特征是区分自我和非自我的能力。在看不到或听不到周围环境的情况下，细胞必须能够感知他们的环境，以吸引可能的互动伙伴或避免潜在的风险。哺乳动物的免疫系统只是多细胞生物体中非自我识别机制的基本必要性的许多例子之一。在微生物中，非自我识别的分子基础仍然没有被完全理解。丝状真菌粗糙脉孢霉是一种拥有多种基因组和遗传工具的模式生物，可以用来研究真核微生物中非自我识别的分子基础。长期以来，这种生物一直被用来研究异核体不亲和性，作为一种机制，通过诱导程序性细胞死亡来限制融合产物在遗传不同的个体之间的传播。我们在粗毛拟青霉的幼体中发现了非自我识别机制，这些机制比最初预期的要复杂得多。事实上，这种真菌使用三层非我识别来避免非我胚种之间的融合。(1)它能够从远处识别非我个体，并在两个非我细胞融合之前避免吸引。(2)某些异体细胞相互吸引接触后，未发生细胞壁破裂(细胞融合的第一步)。(3)两个非自身细胞相互融合后，在几分钟内即可引起细胞死亡反应。这是第一次在丝状真菌的种苗中观察到这些非自我识别机制。这项研究将使用批量分离分析结合下一代测序来确定与所观察到的表型有关的基因。相应的基因将在功能上进行表征。这些实验将为丝状真菌非自我识别的新领域的研究提供基础，也适用于其他真核生物物种的吸引、融合和非自我识别。

With the evolution of multicellularity various challenges arise. The extreme degree of cooperation essential for multicellular existence requires a maximum of coordination and communication between cells. One critical feature for interacting cells in a wide range of organisms is the ability to distinguish self from non-self. Without seeing or hearing their surroundings, cells must be able to sense their environment to attract possible interaction partners or avoid potential risks. The mammalian immune system is only one of many examples for the basic necessity for non-self recognition mechanisms in multicellular organisms. In microbes the molecular basis of non-self recognition is still not fully understood. The filamentous fungus Neurospora crassa is a model organism with many genomic and genetic tools with which to investigate the molecular basis of non-self recognition in eukaryotic microbes. This organism has long been used to study heterokaryon incompatibility as one mechanism to restrict the propagation of fusion products between genetically dissimilar individuals by inducing programmed cell death. We identified non-self recognition mechanisms in N. crassa germlings that are much more sophisticated than initially anticipated. In fact, the fungus uses three layers of non-self recognition to avoid fusion between non-self germlings. (1) It is able to recognize non-self individuals from a distance and to avoid attraction before two non-self cells fuse. (2) After attraction and contact of some non-self cells cell wall breakdown (which is the first step of cell fusion) does not occur. (3) A cell death reaction is induced within minutes after two non-self cells fuse with each other. This is the first time that these non-self recognition mechanisms are observed in germlings of filamentous fungi. This research will identify the genes responsible for the observed phenotypes using bulked segregant analyses in combination with next generation sequencing. The corresponding genes will be functionally characterized. The experiments described in this proposal will provide the basis for a new field of research in non-self recognition in filamentous fungi and which is applicable to attraction, fusion and non-self recognition in other eukaryotic species as well.