Genetics of Programmed Cell Death in Arabidoposis

描述（由申请人提供）：植物和所有高等真核生物一样，必须在发育过程中控制细胞死亡的发生和扩散，并对环境信号做出反应。植物生物学充满了发育程序性细胞死亡（PCD）的例子。植物中PCD的一种特殊形式，被称为超敏反应（Hypersensitive Response， HR），与病原体感染的成功识别和反应密切相关。HR是植物免疫应答的重要组成部分。HR与氧化爆发和向感染部位周围细胞发出促死亡和抗死亡信号有关。虽然对动物PCD控制的分子机制了解很多，但对植物的分子机制知之甚少。本研究以拟南芥为遗传模型，将HR控制作为植物PCD的范例。拟南芥基因组已完全测序，但在序列水平上，动物PCD关键调控因子的显著保守性的分子证据很少。我们是最早认识到利用拟南芥来遗传解剖细胞死亡控制的人之一，并在该领域做出了重大贡献。我们发现并分析了一系列在没有病原体的情况下错误调节hr样细胞死亡的突变体。我们克隆了三个关键的HR调节因子，它们都属于一个基因家族：LSD1和相关基因LOL1 （LSD one Like 1）和LOL2。LSD1的作用是抑制正常HR后不需要的细胞死亡的扩散。来自质膜NADPH氧化酶的超氧化物在此过程中与LSD1协同作用。我们最近证明LSD1与几种蛋白质相互作用，包括功能相关的转录因子（TFs）和假定的“metacaspase”。我们证明了bZIP类的一个TF在HR和感染的基础防御中起作用。其活性可被LSD1拮抗，并在体内与LSD1相互作用。我们打算在接下来的提案期内描述其他与lsd相互作用的tf在细胞死亡和HR中的作用。我们最近还克隆了Isd1突变体特异性失控细胞死亡表型的第二个抑制因子。非常令人惊讶的是，这种抑制因子编码NB-LRR类的抗病蛋白。这是NB-LRR类蛋白首次参与除病原体识别之外的任何过程。我们将研究这种特殊的NB-LRR如何控制hr样细胞死亡的传播。我们最近也证明了三种所谓的“metacaspase”中的两种，通过信息学方法在拟南芥中发现，并且携带定义LSD1蛋白家族的锌指结构域，也在HR和失控细胞死亡中起作用。这是对这些蛋白质功能的第一个定义，并允许我们提出它们作为阳性细胞死亡调节剂的行为的详细表征。

DESCRIPTION (provided by applicant): Plants, like all higher eukaryotes, must control the onset and spread of cell death during development and in response to environmental signals. Plant biology is replete with examples of developmentally programmed cell death (PCD). A specialized form of PCD in plants, termed the Hypersensitive Response (HR) is tightly correlated with successful recognition of, and response to, pathogen infection. The HR is an important part of the plant immune response. HR is associated with an oxidative burst and signaling of pro-and anti-death signals to cells surrounding the infection site. While much is known about the molecular mechanisms of PCD control in animals, very little is known in plants. This proposal uses Arabidopsis as a genetic model with which to understand the control of HR as a paradigm for PCD in plants. The Arabidopsis genome is fully sequenced and there is little molecular evidence for significant conservation of key regulators of animal PCD at the sequence level. We were among the first to recognize the use of Arabidopsis to genetically dissect cell death control and have made significant contributions to the field. We identified and analyzed a series of mutants that mis-regulate HR-like cell death in the absence of pathogen. We cloned three key HR regulators all belonging to one gene family: LSD1 and the related genes LOL1 (LSD One Like 1) and LOL2. LSD1 acts to suppress the spread of unwanted cell death following a normal HR. Superoxide derived from a plasma membrane NADPH oxidase acts in concert with LSD1 in this process. We recently demonstrated that LSD1 interacts with several proteins, including functionally relevant transcription factors (TFs) and putative "metacaspases". We demonstrated that one TF of the bZIP class, functions in HR and in basal defense to infection. Its activity is antagonized by LSD1, and they interact with in vivo. We intend to characterize the role of the other LSD-interacting TFs in cell death and HR in the coming proposal period. We also recently cloned a second suppressor of the idiosyncratic runaway cell death phenotype of the Isd1 mutant. Very surprisingly, this suppressor encodes a disease resistance protein of the NB-LRR class. This is the first time that an NB-LRR class protein has been implicated in any process other than pathogen recognition. We will investigate how this particular NB-LRR controls the spread of HR-like cell death. We also recently demonstrated that two of the three so-called "metacaspases," identified in Arabidopsis by informatics approaches, and carrying the zinc-finger domain that defines the LSD1 protein family, also function in HR and runaway cell death is Isd1. This is the first definition of a function for these proteins, and allows us to propose a detailed characterization of their action as positive cell death regulators.