Journal
PHOTOSYNTHESIS RESEARCH
Volume 151, Issue 3, Pages 235-250Publisher
SPRINGER
DOI: 10.1007/s11120-021-00877-5
Keywords
Antarctica; Ascorbate; Cyclic electron flow; Photosystem I; Psychrophile; ROS
Categories
Funding
- National Science Foundation, Office of Polar Programs [OPP-1056396]
- U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES) [DE-SC0019138]
- National Sciences and Engineering Research Council of Canada (NSERC) [RGPIN-2019-05763]
- University of Ottawa
- U.S. Department of Energy (DOE) [DE-SC0019138] Funding Source: U.S. Department of Energy (DOE)
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The Antarctic alga Chlamydomonas sp. UWO 241 demonstrated robust growth and photosynthetic activity under low temperature, high salinity, and high light conditions, outperforming its mesophilic sister species. UWO 241 exhibited unique photostasis mechanisms, such as higher rates of PSI-driven cyclic electron flow and increased capacity for nonphotochemical quenching.
Under environmental stress, plants and algae employ a variety of strategies to protect the photosynthetic apparatus and maintain photostasis. To date, most studies on stress acclimation have focused on model organisms which possess limited to no tolerance to stressful extremes. We studied the ability of the Antarctic alga Chlamydomonas sp. UWO 241 (UWO 241) to acclimate to low temperature, high salinity or high light. UWO 241 maintained robust growth and photosynthetic activity at levels of temperature (2 degrees C) and salinity (700 mM NaCl) which were nonpermissive for a mesophilic sister species, Chlamydomonas raudensis SAG 49.72 (SAG 49.72). Acclimation in the mesophile involved classic mechanisms, including downregulation of light harvesting and shifts in excitation energy between photosystem I and II. In contrast, UWO 241 exhibited high rates of PSI-driven cyclic electron flow (CEF) and a larger capacity for nonphotochemical quenching (NPQ). Furthermore, UWO 241 exhibited constitutively high activity of two key ascorbate cycle enzymes, ascorbate peroxidase and glutathione reductase and maintained a large ascorbate pool. These results matched the ability of the psychrophile to maintain low ROS under short-term photoinhibition conditions. We conclude that tight control over photostasis and ROS levels are essential for photosynthetic life to flourish in a native habitat of permanent photooxidative stress. We propose to rename this organism Chlamydomonas priscuii.
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