title: Diverse strategies of O2usage for preventing photo-oxidative damage under CO2limitation during algal photosynthesis.
abstract: Photosynthesis produces chemical energy from photon energy in the photosynthetic electron transport and assimilates CO2using the chemical energy. Thus, CO2limitation causes an accumulation of excess energy, resulting in reactive oxygen species (ROS) which can cause oxidative damage to cells. O2can be used as an alternative energy sink when oxygenic phototrophs are exposed to high light. Here, we examined the responses to CO2limitation and O2dependency of two secondary algae, Euglena gracilis and Phaeodactylum tricornutum. In E. gracilis, approximately half of the relative electron transport rate (ETR) of CO2-saturated photosynthesis was maintained and was uncoupled from photosynthesis under CO2limitation. The ETR showed biphasic dependencies on O2at high and low O2concentrations. Conversely, in P. tricornutum, most relative ETR decreased in parallel with the photosynthetic O2evolution rate in response to CO2limitation. Instead, non-photochemical quenching was strongly activated under CO2limitation in P. tricornutum. The results indicate that these secondary algae adopt different strategies to acclimatize to CO2limitation, and that both strategies differ from those utilized by cyanobacteria and green algae. We summarize the diversity of strategies for prevention of photo-oxidative damage under CO2limitation in cyanobacterial and algal photosynthesis.
authors.affiliation: Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan.
authors.forename: Ginga
authors.initials: G
authors.lastname: Shimakawa
authors.affiliation: Research Center for the Development of Intelligent Self-Organized Biomaterials, Research Center for Environmental Bioscience, Department of Bioscience, Kwansei-Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Matsuda
authors.affiliation: Research Center for the Development of Intelligent Self-Organized Biomaterials, Research Center for Environmental Bioscience, Department of Bioscience, Kwansei-Gakuin University, 2-1 Gakuen, Sanda, Hyogo 669-1337, Japan.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Nakajima
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tamoi
authors.affiliation: Department of Advanced Bioscience, Faculty of Agriculture, Kinki University, 3327-204 Nakamachi, Nara 631-8505, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
authors.affiliation: Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan.
authors.forename: Chikahiro
authors.initials: C
authors.lastname: Miyake
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D017377:Diatoms / Q000378:metabolism*; D004579:Electron Transport; D004734:Energy Metabolism; D005056:Euglena gracilis / Q000378:metabolism*; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism*; D010788:Photosynthesis
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen