Analysis of singlet oxygen-mediated chloroplast-nucleus signaling in Arabidopsis

活性氧（Reactive oxygen species， ROS）是植物逆境响应过程中的重要信号。取决于它们的浓度和细胞内定位，每个ROS可能引起氧化损伤或启动信号传导。然而，它们的作用模式知之甚少，阐明每种ROS的精确信号作用面临着同时产生不同ROS的问题。为了克服这些限制，我将使用拟南芥的条件流感突变体作为实验系统，允许解剖ROS信号的复杂性，并专门研究一种特定ROS的生物活性，单线态氧（1O2）。流感中的o2信号依赖于EXECUTER1 （EX1）蛋白的活性。产生1O2的位点和EX1的定位都在叶绿体内。这种接近性表明EX1对1O2信号传导的影响可能发生在1O2释放后不久或释放过程中。我将描述EX1并确定其在启动1O2信号传导过程中的作用。这还没有在任何已知产生1O2的生物体中进行分析。这一目标有望揭示高反应性ROS如何启动信号传导而不是氧化损伤。在1O2释放后立即上调的基因中，编码转录因子的基因明显被过度代表，这意味着一个尚未被广泛探索的转录调控网络触发了o2介导的应答。调控模块将由主要的o2响应转录因子及其靶基因组成，这些基因在将o2衍生的信号转化为o2依赖的生理变化中起关键作用。这些反应的范围从应激适应和改变疾病抵抗力到启动程序性细胞死亡和自杀。我将尝试理解一个看似简单的初始事件，单线态氧的释放，是如何引起基因控制的如此多样的反应的激活的。

Reactive oxygen species (ROS) emerged as important signals during plant stress responses. Depending on their concentration and intracellular localization each ROS may cause oxidative damage or initiate signaling. However, their mode of action is poorly understood and elucidating the precise signaling roles of each ROS faces the problem that distinct ROS are produced simultaneously. To overcome these restraints I will use the conditional flu mutant of Arabidopsis as an experimental system that allows to dissect the complexity of ROS signaling and to specifically investigate the biological activity of one particular ROS, singlet oxygen (1O2). 1O2 signaling in flu depends on the activity of the EXECUTER1 (EX1) protein. The site of 1O2 production and the localization of EX1 are within the chloroplast. This proximity suggests that the impact of EX1 on 1O2 signaling is likely to occur shortly after or during the release of 1O2. I will characterize EX1 and determine its role during initiation of 1O2 signaling. This has not yet been analyzed in any organism known to generate 1O2. This objective is expected to reveal insights into how a highly reactive ROS may initiate signaling rather than oxidative damage. Among up-regulated genes right after the release of 1O2, those encoding transcription factors are clearly overrepresented, implicating an as yet largely unexplored transcriptional regulatory network with triggering 1O2-mediated responses. Regulatory modules will be described consisting of primary 1O2-responsive transcription factors and their target genes that play a key role in transforming 1O2-derived signals into 1O2-dependent physiological changes. These responses range from stress acclimation and modifying disease resistance to the initiation of programmed cell death and committing suicide. I will try to understand how a seemingly simple initial event, the release of singlet oxygen, gives rise to the genetically controlled activation of such diverse responses.