Open AccessDiverse strategies of O2 usage for preventing photo-oxidative damage under CO2 limitation during algal photosynthesis
Author(s) -
Ginga Shimakawa,
Yusuke Matsuda,
Kensuke Nakajima,
Masahiro Tamoi,
Shigeru Shigeoka,
Chikahiro Miyake
Publication year - 2017
Publication title -
scientific reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.24
H-Index - 213
ISSN - 2045-2322
DOI - 10.1038/srep41022
Subject(s) - photosynthesis , phaeodactylum tricornutum , phototroph , algae , cyanobacteria , euglena gracilis , electron transport chain , botany , green algae , biology , photochemistry , environmental chemistry , biophysics , chemistry , chloroplast , biochemistry , bacteria , genetics , gene
Photosynthesis produces chemical energy from photon energy in the photosynthetic electron transport and assimilates CO 2 using the chemical energy. Thus, CO 2 limitation causes an accumulation of excess energy, resulting in reactive oxygen species (ROS) which can cause oxidative damage to cells. O 2 can be used as an alternative energy sink when oxygenic phototrophs are exposed to high light. Here, we examined the responses to CO 2 limitation and O 2 dependency of two secondary algae, Euglena gracilis and Phaeodactylum tricornutum . In E. gracilis , approximately half of the relative electron transport rate (ETR) of CO 2 -saturated photosynthesis was maintained and was uncoupled from photosynthesis under CO 2 limitation. The ETR showed biphasic dependencies on O 2 at high and low O 2 concentrations. Conversely, in P. tricornutum , most relative ETR decreased in parallel with the photosynthetic O 2 evolution rate in response to CO 2 limitation. Instead, non-photochemical quenching was strongly activated under CO 2 limitation in P. tricornutum . The results indicate that these secondary algae adopt different strategies to acclimatize to CO 2 limitation, 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 CO 2 limitation in cyanobacterial and algal photosynthesis.