Date of Award
Doctor of Philosophy (PhD)
Photosystem II is a light-driven water-plastoquinone oxidoreductase present in cyanobacteria, plants, and algae. It is the photosynthetic membrane protein complex responsible for oxidizing water into molecular oxygen, which is necessary for life as we know it. As a multi-subunit membrane-protein-pigment complex, Photosystem II undergoes a complex cycle of assembly, damage, and repair called the Photosystem II lifecycle. This cycle must consistently occur to maintain a high level of photosynthetic activity at the cellular level. Cyanobacteria, oxygenic photosynthetic bacteria, are frequently used as model organisms to study oxygenic photosynthetic processes due to their ease of growth and genetic manipulation. Cyanobacterial PSII structure and function have been well-characterized, but its life cycle is under active investigation. In this work, the state of the field is reviewed and various aspects of the PSII lifecycle are investigated in the cyanobacterium Synechocystis sp. PCC 6803. New tools for investigating the PSII lifecycle are developed and an outlook for how these tools may be used to better understand the PSII lifecycle is discussed. In Chapter 1, current knowledge and recent advances in studying the PSII lifecycle in cyanobacteria are reviewed and discussed. Chapter 2 details the discovery and characterization of a chlorophyll-protein complex in the lifecycle of PSII. In Chapter 3, the development of a CRISPR-inhibition system to reversibly halt synthesis of PSII in Synechocystis sp. PCC 6803 by inhibiting expression of the PSII reaction center protein D2 is described. Chapter 4 discusses the development of a system to reversibly halt the PSII lifecycle mid-way by controlling expression of the PSII assembly factor CtpA, and Chapter 5 discusses findings about an overexpression strain of the PSII assembly factor Psb27. In Chapter 6, conclusions and future directions from each chapter, as well as additional data, are summarized.
Chair and Committee
Himadri B. Pakrasi
Johnson, Virginia M., "Assembly and Repair of Photosystem II" (2022). Arts & Sciences Electronic Theses and Dissertations. 2677.