The Role of the Cia5 Gene in the Carbon Concentrating Mechanism in Chlamydomonas Reinhardtii

碳浓缩机制（CCM）在地球的光合生产力和碳循环能力中起着重要作用。 CCM是衣原体和大多数其他真核和原核藻类在大气CO2水平下进行光合作用所必需的。 获得的关于C中CCM的知识。通过这个为期三年的项目，再加上来自其他实验室的信息，应该可以更全面地了解藻类细胞是如何在二氧化碳有限的水环境中生存和繁殖的。 本研究的主要目的是阐明莱茵衣藻CCM的组成和调控机制。 该项目的重点是Cia5基因的完整特征及其作为细胞对环境CO2和HCO3浓度变化反应的主要调节剂的作用。 基于目前证据的重要性，Cia5基因编码的转录因子是一个或多个信号转导级联的一部分，该级联允许或逆转功能性CCM的形成。 全面表征Cia5基因的实验概述了Cia5蛋白的研究，其亚细胞定位，翻译后修饰，DNA结合特异性和其他功能所需的控制CCM的组装。 提出了一个模型，其中CIA5蛋白可以作为基因转录的诱导物或阻遏物，这些基因的表达在细胞从高CO2水平向低CO2水平转变期间急剧增加。 实验概述，将解决的不确定性，是否CIA 5作为一个诱导剂或基因表达的阻遏物。 从长远来看，对CCM的进一步了解具有在农业中实际应用的潜力。 例如，某些作物已被证明在二氧化碳浓度升高的情况下产量更高。 如果CCM的适当部分可以转移到这些作物上，它们增加内部CO2浓度的结果可能会大大提高作物产量。

The carbon concentrating mechanism (CCM) plays a major role in the earth'sphotosynthetic productivity and its capacity to cycle carbon. The CCM isessential for photosynthesis at atmospheric levels of CO2 in Chlamydomonasand most other eukaryotic and prokaryotic algae. Knowledge gainedregarding the CCM in C. reinhardtii through this three-year project,coupled with information from other laboratories, should allow a morecomplete understanding of how algal cells are able to survive and flourishin their CO2-limited, aqueous environment. The primary goal of thisresearch project is to elucidate components and mechanisms of regulation ofthe CCM in Chlamydomonas reinhardtii. The focus of the project is thecomplete characterization of the Cia5 gene and its role as a masterregulator of the cell's response to changes in environmental CO2 and HCO3concentrations. Based on the weight of present evidence, it appears theCia5 gene encodes a transcription factor that is part of one or more signaltransduction cascades that allow, or reverse, formation of a functionalCCM. Experiments to fully characterize the Cia5 gene are outlined alongwith studies of the CIA5 protein, its subcellular location,post-translational modification(s), DNA binding specificities and otherfeatures required for its function in controlling assembly of the CCM. Amodel is proposed in which the CIA5 protein could act either as an induceror repressor of transcription of genes whose expression is dramaticallyincreased during a shift of cells from high to low CO2 levels. Experimentsare outlined that will resolve the uncertainty of whether CIA5 acts as aninducer or repressor of gene expression. In the long term, an increasedunderstanding of the CCM has the potential for practical application inagriculture. For example, certain crop plants have been demonstrated toproduce higher yields under elevated levels of CO2. If appropriateportions of the CCM can be transferred to those crops, their resultantability to increase internal CO2 concentrations could lead to substantiallyimproved crop yields.