Analysis of Programmed Cell Death in Filamentous Fungi

描述（由申请人提供）：拟进行的研究的主要目的是利用粗神经孢子虫作为模型系统，剖析丝状真菌非自我识别的分子机制。非自我识别导致一种真菌程序性细胞死亡（PCD）称为异核不相容（HI）。HI在丝状真菌中普遍存在，可以被比作真菌的“免疫”系统，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，从而赋予选择性优势。丝状真菌营养生长过程中的非自我识别是由称为het（异核体）的遗传位点介导的。与其他非自我识别的基因座类似，如颌骨脊椎动物的主要组织相容性复合体（MHC），草棘牛的这些基因座显示出平衡选择的证据。在我们之前的资助期内，我们发现了一种非自我识别和死亡所需的新蛋白质，称为PIN-C，它包含真菌特异性死亡效应域，称为HET。我们确定HI细胞死亡不是通过凋亡机制发生的，尽管活性氧是一个与非自我识别相关的早期事件。我们还发现了一种称为vib-1（植物不相容性阻断）的转录因子，它是细胞死亡和正常分泌所必需的。最后，我们最近的数据表明，调节非自我识别的基因干扰了趋化性相互作用和细胞融合所需的信号传导，从而表明与趋化性/细胞融合相关的信号传导/机制与非自我识别蛋白和细胞死亡之间存在有趣的联系。在本文中，我们描述了进一步剖析非自我识别分子机制的实验，揭示了死亡途径，并利用基因组学方法鉴定了新的非自我识别基因座。最后，我们描述了一些实验，以检查参与融合和非自我识别的细胞信号之间令人兴奋的联系，这是我们最近确定发生在远处的一个方面。我们相信，利用N. crassa作为模式生物对真菌PCD进行解剖是开发抗人类真菌感染药物的一个有吸引力的真菌特异性靶点，并为非自我识别位点的进化研究提供了一个迷人的比较模型。

DESCRIPTION (provided by applicant): The primary goal of the proposed studies is to dissect the molecular mechanism of nonself recognition in filamentous fungi using Neurospora crassa as a model system. Nonself recognition leads to a type of fungal programmed cell death (PCD) termed heterokaryon incompatibility (HI). HI is ubiquitous in filamentous fungi and can be likened to a fungal "immune" system, which confers selective advantages by preventing hyphal fusion events that spread mycoviruses, debilitated organelles and deleterious plasmids throughout a fungal population. Nonself recognition during vegetative growth in filamentous fungi is mediated by genetic loci, termed het (for heterokaryon). Similar to other nonself recognition loci, such as the Major Histocompatibility Complex (MHC) in jawed vertebrates, het loci in N. crassa show evidence of balancing selection. From our previous funding period, we identified a new protein required for nonself recognition and death, called PIN-C, which contains a fungal-specific death effector domain, called HET. We determined that cell death through HI does not occur via an apoptotic mechanism, although reactive oxygen species are an early event associated with nonself recognition. We also identified a transcription factor called vib-1 (vegetative incompatibility blocked) that is required both for cell death and for proper secretion. Finally, we have very recent data indicating that the genes that regulate nonself recognition interfere with signaling required for chemotropic interactions and cell fusion, thus indicating an intriguing link between signaling/machinery associated with chemotropism/cell fusion and nonself recognition proteins and cell death. In this proposal, we describe experiments to further dissect the molecular mechanism of nonself recognition, unravel the pathway to death and identify new nonself recognition loci using genomics approaches. Finally, we describe experiments to examine the exciting connection between cell signaling involved in fusion and nonself recognition, an aspect that we recently determined occurs at a distance. We believe that a dissection of fungal PCD using N. crassa as a model organism is an attractive fungal-specific target for the development of drugs to combat human fungal infections and provides a fascinating comparative model for evolutionary studies on nonself recognition loci.