Extreme Engineering: How Antarctic Algae Adapt to Hypersalinity

Julkowska, Magdalena

doi:10.1104/pp.20.00467

“…High ATP production may suggest a lower requirement for reductant under permanent environmental stress where growth and assimilation rates could be slow. The adjustments to the photosynthetic apparatus are accompanied by alterations in carbon metabolism, including upregulation of several enzymes within the Calvin Benson Bassham cycle (CBB), and key enzymes of the shikimate pathway, a high carbon flux pathway which synthesizes precursors for aromatic metabolites (Julkowska, 2020;Kalra et al, 2020). Together, these novel adaptive strategies allow UWO 241 to maintain robust growth and photosynthesis under the combined stress of permanent low temperature and high salinity.…”

Section: Introductionmentioning

confidence: 99%

Cyclic electron flow and ascorbate pathway play a role in survival of Chlamydomonas sp. UWO241 to long-term photooxidative stress

Stahl-Rommel

¹

,

Kalra

²

,

D’Silva

³

et al. 2020

Preprint

0

View full text Add to dashboard Cite

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.

show abstract

“…The additional proton motive force (pmf) derived from CEF is used for constitutive capacity for NPQ and production of additional ATP in cells grown under high salinity (Kalra et al, 2020). The adjustments to the photosynthetic apparatus are accompanied by alterations in carbon metabolism, including upregulation of several enzymes within the Calvin Benson Bassham cycle (CBB), and key enzymes of the shikimate pathway, a high carbon flux pathway which synthesizes precursors for aromatic metabolites (Julkowska, 2020;Kalra et al, 2020). Together, these novel adaptive strategies allow UWO 241 to maintain robust growth and photosynthesis under the combined stress of permanent low temperature and high salinity.…”

Section: Introductionmentioning

confidence: 99%

Cyclic electron flow and ascorbate pathway play a role in survival of Chlamydomonas sp. UWO241 to long-term photooxidative stress

Rommel

¹

,

Kalra

²

,

Silva

³

et al. 2020

Preprint

0

View full text Add to dashboard Cite

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.

show abstract