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Cyclic electron flow and ascorbate pathway play a role in survival of Chlamydomonas sp. UWO241 to long-term photooxidative stress
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  • Sarah Stahl-Rommel,
  • Isha Kalra,
  • Susanna D'Silva,
  • Mark Hahn,
  • Marina Cvetkovska,
  • Rachael Morgan-Kiss
Sarah Stahl-Rommel
Miami University College of Arts and Science
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Isha Kalra
Miami University College of Arts and Science
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Susanna D'Silva
Miami University College of Arts and Science
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Mark Hahn
Miami University College of Arts and Science
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Marina Cvetkovska
University of Ottawa
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Rachael Morgan-Kiss
Miami University College of Arts and Science
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Abstract

Under environmental stress plants and algae employ a variety of strategies to avoid damage to the photosynthetic apparatus and maintain photosynthetic capacity. To date, most studies on stress acclimation have focused on model organisms possessing limited tolerance to elevated stress levels. We compared the long-term acclimatory capacities of a mesophilic alga (Chlamydomonas raudensis SAG 49.72; SAG 49.72) and an Antarctic halotolerant psychrophile (Chlamydomonas sp. UWO 241; UWO 241) by monitoring photobiology, cyclic electron flow (CEF) and ROS defense in cultures acclimated to long-term low temperature, high salinity or high light stress. SAG 49.72 responded to long-term stress by increasing chlorophyll a/b ratio and redistributing absorbed light energy from photosystem II (PSII) to photosystem I (PSI). In contrast, the psychrophile exhibited faster half times for P700+ re-reduction under all treatments, suggesting high CEF rates. High CEF was accompanied by increased capacity for nonphotochemical quenching. Last, UWO 241 exhibited constitutively high activity of two key ascorbate cycle enzymes, ascorbate peroxidase and glutathione reductase, as well as a large ascorbate pool. Our results suggest that UWO 241 relies on high PSI-mediated CEF and ROS detoxification to protect the photosynthetic apparatus while minimizing energy expenditure on repairs.

Peer review status:UNDER REVIEW

15 Aug 2020Submitted to Plant, Cell & Environment
15 Aug 2020Assigned to Editor
15 Aug 2020Submission Checks Completed
17 Aug 2020Reviewer(s) Assigned
21 Aug 2020Review(s) Completed, Editorial Evaluation Pending