Singlet Oxygen Signaling

描述（由申请人提供）：好氧生物，从细菌到植物和动物，已经进化出了传感、信号传导和保护机制，以应对细胞内外不可避免地产生的各种活性氧（ROS）。阐明这些机制是一个具有广泛生物学意义的问题。虽然细胞对过氧化氢和超氧化物等活性氧的反应已经被广泛研究，但对单线态氧的生物反应知之甚少，单线态氧是一种特别有毒的活性氧，会对许多关键的细胞成分造成氧化损伤，如不饱和脂质、蛋白质和DNA。单线态氧通常由光敏反应产生，这是在患有卟啉症和可能与年龄相关的黄斑变性的人类中观察到的光氧化性组织损伤的基础。另一方面，光敏化已被用于某些人类癌症的光动力治疗策略。本研究旨在利用分子遗传学和基因组学的方法分析单细胞绿藻莱茵衣藻（Chlamydomonas reinhardtii）的单线态氧适应反应，以解决单线态氧信号传导方面的知识相对不足。与其他富氧光养生物一样，衣藻必须应对高浓度的内源性氧和叶绿素（一种有效的光敏剂），因此可能进化出特别强大的机制来感知和响应单线态氧。本课题的具体目的是：(1)对衣藻单线态氧驯化反应进行生理生化表征；(2)利用全基因组微阵列分析鉴定单线态氧驯化过程中表达变化的基因；(3)利用反向遗传学方法检验单线态氧驯化中特定候选基因的必要性；(4)对单线态氧驯化进行正向遗传剖析。包括(5)分离出已经鉴定的驯化突变体（称为sos1）中有缺陷的基因。这项研究将有助于阐明其他生物中单线态氧生物学的研究，并为真核细胞如何感知和响应单线态氧提供基础知识。

DESCRIPTION (provided by applicant): Aerobic organisms, from bacteria to plants and animals, have evolved sensing, signaling, and protective mechanisms to cope with various reactive oxygen species (ROS) that are inevitably generated both intra- and extracellularly. Elucidation of these mechanisms is a problem of broad biological significance. Although cellular responses to ROS such as hydrogen peroxide and superoxide have been extensively studied, relatively little is known about biological responses to singlet oxygen, an especially toxic type of ROS that causes oxidative damage to numerous critical cellular components, such as unsaturated lipids, proteins, and DNA. Singlet oxygen is commonly generated by photosensitization reactions that are the basis for the photooxidative tissue damage observed in humans suffering from porphyria and possibly age-related macular degeneration. On the other hand, photosensitization has been exploited in strategies for photodynamic therapy of certain human cancers. This proposal aims to address the relative deficiency of knowledge about singlet oxygen signaling by using molecular genetic and genomic approaches to dissect the singlet oxygen acclimation response in a unicelluar green alga, Chlamydomonas reinhardtii, a model photosynthetic eukaryote. Like other oxygenic phototrophs, Chlamydomonas must cope with high endogenous concentrations of both oxygen and chlorophyll, a potent photosensitizer and may therefore have evolved particularly robust mechanisms for perceiving and responding to singlet oxygen. The specific aims of this proposal are (1) to perform physiological and biochemical characterization of the singlet oxygen acclimation response in Chlamydomonas, (2) to use whole-genome microarray analysis to identify the set of genes whose expression changes during acclimation to singlet oxygen, (3) to use reverse genetics approaches to test the necessity of specific candidate genes in singlet oxygen acclimation, and (4) to perform a forward genetic dissection of singlet oxygen acclimation, including (5) the isolation of a gene that is defective in an already identified acclimation mutant, called sos1. This investigation will help illuminate studies of singlet oxygen biology in other organisms and provide fundamental knowledge about how eukaryotic cells sense and respond to singlet oxygen.