蓝藻信号转导系统的比较基因组学分析及重要基因功能的验证

IOCAS-IR > 海洋环流与波动重点实验室

	蓝藻信号转导系统的比较基因组学分析及重要基因功能的验证
其他题名	Comparative genomic analysis of cyanobacterial signal transduction system and functional study of some important genes
	张晓雯
学位类型	博士
	2008-06-11
学位授予单位	中国科学院海洋研究所
学位授予地点	海洋研究所
关键词	蓝藻信号转导丝氨酸/苏氨酸激酶二元信号转导系统比较基因组学
摘要	蓝藻经过漫长的进化，在地球上具有极其广范的分布，而且对环境胁迫具有极强的耐受性，这其中信号转导系统起了至关重要的作用。蓝藻信号转导系统主要包括二元信号转导系统和丝氨酸/苏氨酸激酶。蓝藻全基因组测序工作的完成为蓝藻信号转导系统的研究奠定了基础。目前国外对蓝藻信号转导系统的研究主要集中在对单个蓝藻的单个信号系统的功能研究。本论文首先采用比较基因组学的方法对蓝藻中的两大信号转导系统从分布、结构及进化等角度进行了系统的分析，进而对其中重要信号转导基因的功能进行了验证。通过比较基因组学分析发现蓝藻中的信号转导系统的分布、结构特征与物种的生理、生态特征之间关系密切；蓝藻中丝氨酸/苏氨酸激酶具有与真核型激酶类似的催化方式；在信号转导系统的进化过程中存在着基因复制、缺失、附属功能域的获得及随机重排等复杂的进化现象；且二元信号转导系统中相互作用的组氨酸激酶与反应调控蛋白之间并不是完全同步的进化关系，可能有着不同的进化历程。该研究建立了蓝藻信号转导系统中的基因-结构-功能的框架结构，为其功能的研究奠定了基础。聚球藻PCC7942和集胞藻PCC6803是单细胞的淡水蓝藻，具有天然的外源DNA转化系统，是蓝藻分子遗传学研究的模式生物。通过基因突变的方法对这两株蓝藻中二元信号转导系统的部分重要反应调控蛋白同源基因rre28和syn7942_0095的功能进行了验证，发现高度保守的同源序列在这两株蓝藻中起着不同的作用，且一个组氨酸激酶可能与不同的反应调控蛋白相互作用，说明同源序列的功能在进化的过程中已经发生了分化。目前对蓝藻信号转导系统中丝氨酸/苏氨酸激酶的功能研究较少。通过基因突变及表达差异分析发现集胞藻PCC6803中的丝氨酸/苏氨酸激酶SpkG参与高盐胁迫的信号传递。通过高盐胁迫条件下SpkG对整个转录图谱影响的研究，发现了60个差异表达基因，涉及转运、能量传递、蛋白加工修饰和信号转导等多个生理过程。该研究首次通过实验验证了蓝藻中的丝氨酸/苏氨酸激酶对环境胁迫的响应，并首次发现由二元信号转导系统和丝氨酸/苏氨酸激酶共同参与的对逆境胁迫的调控网络。蓝藻兼具细菌和植物的特点，蓝藻成熟的转化体系也为真核生物基因功能的研究提供了新的模式宿主。蓝藻信号转导系统中激酶功能的研究为我们进一步研究真核生物激酶的功能提供借鉴，且对蓝藻信号转导的研究将对植物的抗逆胁迫研究提供重要的理论依据。
其他摘要	During the long evolutionary history, cyanobacteria have developed a variety of response mechanisms to sense external or internal factors and to cope with the changing environmental conditions. The signal transduction system of cyanobacteria is constituted of two-component signal transduction system and eukaryotic-type serine/threonine kinases. Functional study was now mainly on one signal transduction system and in one cyanobacteria strain. In this study, comparative genomic analysis of the main cyanobacterial signal transduction systems has been employed. And then functions of some important genes have been examined. The number of genes in cyanobacterial signal transduction systems was the result of the genome size, ecophysiology, and physiological properties of the organisms. Similar conserved motifs and amino acids indicate that cyanobacterial STKs make use of a similar catalytic mechanism as eukaryotic STKs. Gain-and-loss is significant during the evolution of genes in cyanobacterial signal transduction systems, along with domain shuffling and insertion. Histidine kinases and response regulators in two-component signal transduction system may have different evolutionary history. This study has established an overall framework of sequence-structure-function interactions for the family of siganal transduction genes, which will be useful for the functional analysis. Synechococcus PCC7942 and Synechocystis PCC6803 are unicellular cyanobacteria in freshwater, which can be transformed naturally and is the model speices of molecular genetics of cyanobacteria. Funtion of two orthologous genes, synpcc7942_0095 and rre28, in Synechococcus and Synechocystis separately have been analyzed. We found that these two highly conserved orthologous genes have different functions. And the same histidine kinase could be activated different response regulators in different cyanobacteria strains. This phenomenon may be explained by the functional differentiation during the long evolutional history. Studies on serine/threonine kinases in cyanobacteria were limited. We have found that the serine/threonine kinase of SpkG in Synechocystis PCC6803was indicated to be involved in adaptation to high salt stress by mutant and RT-PCR analysis. We analyzed global gene expression in both the SpkG mutant and wild strain under normal and high salt conditions. Sixty genes have been found expressed differently in wild strain and SpkG mutant, which were mainly consisted of transport, energy metabolism, protein processing, envelope biogenesis and signal transduction. It is for the first time to confirm a serine/threonine kinase and two-component signal transduction system together constituting a complex network under high salt condiotion. Cyanobacteria have the characters of both bacteria and plant. The evolutional and ecologic dominance has made cyanobacteria important for the study of signal transduction systems. The availability of multiple sequenced genomes has been very helpful in phylogenetic and functional studies of cyanobacterial genes. And the study of signal transduction systems in cyanobacteria may provide important clues for the stress study of plants.
页数	160
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/279
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	张晓雯. 蓝藻信号转导系统的比较基因组学分析及重要基因功能的验证[D]. 海洋研究所. 中国科学院海洋研究所,2008.

条目包含的文件
文件名称/大小	文献类型	版本类型	开放类型	使用许可
10001_20061800681200（6435KB）			限制开放	--	浏览