title: Up-regulation of photoprotection and PSII-repair gene expression by irradiance in the unicellular green alga Dunaliella salina.
abstract: 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.
authors.affiliation: Department of Life Science, Hanyang University, Seoul, South Korea.
authors.forename: Seunghye
authors.initials: S
authors.lastname: Park
authors.forename: Juergen E W
authors.initials: JE
authors.lastname: Polle
authors.forename: Anastasios
authors.initials: A
authors.lastname: Melis
authors.forename: Taek Kyun
authors.initials: TK
authors.lastname: Lee
authors.forename: Eonseon
authors.initials: E
authors.lastname: Jin
mesh_terms: D020418:Algal Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000145:classification* / Q000235:genetics; D015152:Blotting, Northern; D000460:Chlorophyta / Q000235:genetics / Q000502:physiology*; D020224:Expressed Sequence Tags; D015870:Gene Expression / Q000235:genetics / Q000502:physiology*; D015723:Gene Library; D008027:Light; D008969:Molecular Sequence Data; D045332:Photosystem II Protein Complex / Q000235:genetics; D012313:RNA / Q000032:analysis; D015854:Up-Regulation
chemical_list: D020418:Algal Proteins; D045332:Photosystem II Protein Complex; D012313:RNA