Analysis of programmed cell death in filamentous fungi

描述（由申请人提供）：拟议研究的主要目标是利用粗神经孢子虫作为模型系统，从遗传学角度剖析丝状真菌非自我识别导致真菌程序性细胞死亡（PCD）的机制。非自我识别是防御病原体入侵和防止资源掠夺的必要条件。我们的假设是丝状真菌，如粗神经孢子虫，利用蛋白质异质复合体的形成作为一种机制来完成非自我识别，从而导致真菌PCD。丝状真菌营养生长过程中的非自我识别是由遗传位点介导的，称为het（异核体）位点，它调节因遗传不同个体之间菌丝融合而产生的异核体的活力，het位点显示平衡选择的证据，类似于主要组织相容性复合体（MHC）中的位点，这是哺乳动物免疫系统的一部分。异核不相容是细胞程序性死亡的一种形式，可以定义为细胞主动参与自身死亡的有序过程。异核不相容是一种真菌“免疫”系统，它通过防止菌丝融合事件在真菌种群中传播分枝病毒、衰弱的细胞器和有害的质粒，赋予丝状真菌选择优势。我们的初步结果（由我们之前的NIH资助支持）表明，非自我识别是通过与质膜相关的HET-C蛋白异复合体的形成发生的，其稳定性/结构似乎与HET-C单体有根本不同。我们的数据表明，HET- c与携带HET结构域的第二种蛋白相互作用；HET结构域基因在丝状真菌基因组中很常见，但功能未知，包括人类真菌病原体。这种蛋白复合物的形成激活了信号转导机制和基因调控，最终导致异核细胞的死亡和破坏。本实验旨在进一步研究HET-C/VIB-2异复合体在非自我识别中的作用，以及MAP激酶途径和VIB-1转录调节因子在触发真菌PCD中的作用。我们相信，对真核生物中丝状真菌PCD的解剖将阐明PCD的保守性和差异性特征，为致病性丝状真菌提供潜在的药物靶点。

DESCRIPTION (provided by applicant): The primary goal of the proposed studies genetically dissect the mechanism of nonself recognition in filamentous fungi which leads to fungal programmed cell death (PCD) using Neurospora crassa as a model system. Nonself recognition is essential for defense against pathogen invasion and prevention of resource plundering. Our hypothesis is that filamentous fungi, such as Neurospora crassa, have harnessed protein heterocomplex formation as a mechanism to accomplish nonself recognition, which leads to fungal PCD. Nonself recognition during vegetative growth in filamentous fungi is mediated by genetic loci, termed het (for heterokaryon) loci, which regulate the viability of heterokaryons that occur as a result of hyphal fusion between genetically different individuals, het loci show evidence of balancing selection, similar to loci within the Major Histocompatibility Complex (MHC) which are part of the mammalian immune system. Heterokaryon incompatibility is a form of programmed cell death, which can be defined as an orderly process in which a cell actively participates in its own death. Heterokaryon incompatibility is a fungal "immune" system that confers selective advantages to filamentous fungi by preventing hyphal fusion events that spread mycoviruses, debilitated organelles and deleterious plasmids throughout a fungal population. Our initial results (supported by our previous NIH grant) show that nonself recognition occurs by formation of a HET-C protein heterocomplex associated with the plasma membrane, which appears to be fundamentally different in stability/structure than HET-C monomers. Our data suggests that HET-C interacts with a second protein carrying a HET domain; HET domain genes are common, but of unknown function, in filamentous fungal genomes, including human fungal pathogens. This protein complex formation activates signal transduction mechanisms and gene regulation, ultimately resulting in death and destruction of the heterokaryotic cell. The experiments described in this proposal aim to further investigate the role the HET-C/VIB-2 heterocomplex in nonself recognition, and MAP kinase pathways and the VIB-1 transcriptional regulator in triggering fungal PCD. We believe that a dissection of fungal PCD in N. crassa will illuminate conserved and divergent features of PCD among eukaryotic organisms, provide potential drug targets for pathogenic filamentous fungi.