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DISSERTATION_KALRA_07162021.pdf (3.85 MB)

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Role of Cyclic Electron Flow (CEF) and Photosystem I (PSI) Supercomplex Formation During Acclimation to Long-Term Salinity Stress in Green Algae: A Comparative Study

Kalra, Isha
http://orcid.org/0000-0002-6185-9893
http://rave.ohiolink.edu/etdc/view?acc_num=miami1626448523546503

Abstract Details

2021, Doctor of Philosophy, Miami University, Microbiology.
Photosynthesis is one of the most important processes on Earth by which organisms convert solar energy into usable forms of energy. Linear electron flow (LEF) and cyclic electron flow (CEF) constitute two major pathways in photosynthesis. While LEF leads to production of both ATP and NADPH, CEF only produces ATP that helps balance the ATP:NADPH ratio required for carbon fixation. CEF also plays a major role during acclimation to several environmental stressors. However, the regulation and mechanism by which CEF operates is still not clearly understood. Recent studies have shown that formation of a protein supercomplex with PSI appears to be essential for induction of CEF in several model organisms. However, both supercomplex formation and CEF induction have been mainly studied under short-term, transitory stress conditions. In addition, the role and mechanism by which organisms may rely on CEF to survive in their natural habitat and acclimate to stress over a long period of time has not been considered. In this study we compared how three photosynthetic organisms (one model alga, Chlamydomonas reinhardtii; two extremophiles, C sp. UWO241 and C. sp. ICE-MDV) utilize CEF to cope with their natural environment and adapt to steady-state environmental stress. To that end, the objectives of this thesis were i) to elucidate the role of CEF in long-term salinity acclimation ii) to understand the downstream changes associated with increased CEF, and iii) to identify whether PSI-supercomplexes are associated with increased CEF during salinity acclimation. We hypothesized that a stable PSI-supercomplex is required for high CEF, which in turn supports strong carbon fixation capacity for production of downstream metabolic products important for long-term acclimation to salinity stress. We showed for the first time, that increased CEF in UWO241 leads to excess ATP production and rewiring of downstream metabolism under high salinity. Next, we showed that a laboratory evolved salinity-tolerant strain of model C. reinhardtii uses constitutive upregulation of CEF to deal with salinity stress, which is in-turn associated with increased non-photochemical quenching and rewired carbon metabolism. Last, we show that CEF is involved in salinity acclimation in all three Chlamydomonas species, regardless of their salinity tolerance. We also show that PSI-supercomplexes are associated with increased CEF in these species. Characterization of high-salt supercomplex of C. reinhardtii revealed that it shares many similarities with the extensively described state 2 supercomplex, and that supercomplex composition might be species dependent rather than stress dependent.
Rachael Morgan-Kiss (Advisor)
Xin Wang (Committee Member)
Annette Bollmann (Committee Member)
Donald Ferguson (Committee Member)
Carole Dabney-Smith (Committee Member)
Luis Actis (Committee Member)
235 p.
Biochemistry; Ecology; Environmental Science; Microbiology; Physiology; Plant Biology
photosynthesis; CEF; supercomplex; extremophile; salinity stress; acclimation; adaptation; Antarctic; metabolism; chlamydomonas

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Citations

  • Kalra, I. (2021). Role of Cyclic Electron Flow (CEF) and Photosystem I (PSI) Supercomplex Formation During Acclimation to Long-Term Salinity Stress in Green Algae: A Comparative Study [Doctoral dissertation, Miami University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=miami1626448523546503

    APA Style (7th edition)

  • Kalra, Isha. Role of Cyclic Electron Flow (CEF) and Photosystem I (PSI) Supercomplex Formation During Acclimation to Long-Term Salinity Stress in Green Algae: A Comparative Study. 2021. Miami University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=miami1626448523546503.

    MLA Style (8th edition)

  • Kalra, Isha. "Role of Cyclic Electron Flow (CEF) and Photosystem I (PSI) Supercomplex Formation During Acclimation to Long-Term Salinity Stress in Green Algae: A Comparative Study." Doctoral dissertation, Miami University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1626448523546503

    Chicago Manual of Style (17th edition)

miami1626448523546503
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This open access ETD is published by Miami University and OhioLINK.