Park Seunghye, Polle Juergen E W, Melis Anastasios, Lee Taek Kyun, Jin Eonseon
Department of Life Science, Hanyang University, Seoul, South Korea.
Mar Biotechnol (NY). 2006 Mar-Apr;8(2):120-8. doi: 10.1007/s10126-005-5030-4. Epub 2006 Mar 15.
The unicellular green alga Dunaliella salina is an attractive model organism for studying photoacclimation responses and the photosystem II (PSII) damage and repair process in the photosynthetic apparatus. Irradiance during cell growth defines both the photoacclimation and the PSII repair status of the cells. To identify genes specific to these processes, a cDNA library was created from irradiance-stressed D. salina. From the cDNA library, 1112 randomly selected expressed sequence tags (ESTs) were analyzed. Because ESTs constitute the expressed part of the genome, the strategy of randomly sequencing cDNA clones at their 5'-ends allowed us to obtain information about the transcript level of numerous genes in light-stressed D. salina. The results of a BLASTX search performed on the obtained total set of ESTs showed that approximately 1% of the ESTs could be assigned to genes coding for proteins that are known to be up-regulated in response to high-light stress. Specifically, after 48 h of high-light exposure of the cells, an increase in the expression level of antioxidant genes, such as Fe-SOD and APX, was observed, as well as elevated levels of the Cbr transcript, a light-harvesting Chl-protein homolog. Further, the ATP-dependent Clp protease gene was also up-regulated in D. salina cells after 48 h of exposure to high light. The results provide initial insight into the global gene regulation process in response to irradiance.
单细胞绿藻杜氏盐藻是研究光合适应反应以及光合装置中光系统II（PSII）损伤与修复过程的一种有吸引力的模式生物。细胞生长期间的光照强度决定了细胞的光合适应以及PSII修复状态。为了鉴定这些过程的特异性基因，构建了一个来自受光照胁迫的杜氏盐藻的cDNA文库。从该cDNA文库中，分析了1112个随机选择的表达序列标签（EST）。由于EST代表基因组的表达部分，对cDNA克隆的5'端进行随机测序的策略使我们能够获得有关光照胁迫下杜氏盐藻中众多基因转录水平的信息。对获得的全部EST进行BLASTX搜索的结果表明，约1%的EST可归为编码已知在高光胁迫下上调的蛋白质的基因。具体而言，在细胞高光照射48小时后，观察到抗氧化基因如铁超氧化物歧化酶（Fe-SOD）和抗坏血酸过氧化物酶（APX）的表达水平增加，以及捕光叶绿素蛋白同源物Cbr转录本水平升高。此外，在高光照射48小时后，杜氏盐藻细胞中的ATP依赖性Clp蛋白酶基因也上调。这些结果为响应光照强度的全局基因调控过程提供了初步见解。
