Genetics of Programmed Cell Death in Arabidoposis

描述（由申请人提供）：植物，像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。植物中的一种特殊形式的PCD，称为过敏反应（HR），与成功识别和响应病原体感染密切相关。HR是植物免疫应答的重要组成部分。HR与氧化爆发以及向感染部位周围的细胞发出促死亡和抗死亡信号相关。虽然对动物中PCD控制的分子机制了解很多，但对植物知之甚少。该建议使用拟南芥作为遗传模型，以了解HR的控制作为植物PCD的范例。拟南芥的基因组是完全测序，并有动物PCD的关键调控在序列水平上的显着保守的分子证据很少。我们是最早认识到利用拟南芥基因解剖细胞死亡控制，并作出了重大贡献的领域。我们鉴定并分析了一系列突变体，这些突变体在没有病原体的情况下错误调节HR样细胞死亡。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：LSD 1和相关基因LOL 1（LSD One Like 1）和LOL 2。LSD 1的作用是抑制正常HR后不必要的细胞死亡的扩散。在此过程中，来自质膜NADPH氧化酶的超氧化物与LSD 1协同作用。我们最近证明，LSD 1与几种蛋白质相互作用，包括功能相关的转录因子（TF）和推定的“后半胱氨酸蛋白酶”。我们证明了一个TF的bZIP类，功能在HR和基础防御感染。它的活性被LSD 1拮抗，并且它们在体内相互作用。我们打算在未来的提案期内描述其他LSD相互作用TF在细胞死亡和HR中的作用。我们最近还克隆了第二个抑制因子的特异质失控细胞死亡表型的Isd 1突变体。非常令人惊讶的是，该抑制基因编码NB-LRR类的抗病蛋白。这是NB-LRR类蛋白首次参与病原体识别以外的任何过程。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。我们最近还证明，在拟南芥中通过信息学方法鉴定的三种所谓的“metacaspase”中的两种，携带定义LSD 1蛋白家族的锌指结构域，也在HR和失控细胞死亡中起作用，是Isd 1。这是这些蛋白质功能的第一个定义，并使我们能够提出一个详细的表征其作为积极的细胞死亡调节剂的作用。

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.