Public Abstract

DE-SC0020639: Protein phosphorylation and oxidative protein modification in photosystem II disassembly and repair

Award Status: Active

Institution: Purdue University, West Lafayette, IN
UEI: YRXVL4JYCEF5
PM: Brown, Katherine

Most Recent Award Date: 07/29/2026
Number of Support Periods: 7
PI: Puthiyaveetil, Sujith

Current Budget Period: 09/01/2026 - 05/31/2027
Current Project Period: 09/01/2026 - 05/31/2027

Public Abstract

Photosynthesis by plants, algae, and certain bacteria capture light energy and convert it to chemical energy. To accomplish this, two photosystems operate in concert to harvest light energy and drive the primary light-driven electron transport reactions of photosynthesis, among which photosystem II (PSII) is particularly vulnerable to light-induced damage. This project seeks to elucidate how post-translational modifications promote the disassembly and repair of PSII and the structural basis of the PSII repair process. The reaction center protein D1, located at the core of PSII, is the primary target of photodamage. To maintain photosynthetic efficiency, a repair cycle replaces the damaged D1 subunit with a newly synthesized copy, but the mechanism by which the large PSII antenna-core supercomplexes disassemble for repair has remained unclear. Our recent research reveals a role for protein phosphorylation and oxidative protein modifications in facilitating the disassembly of PSII antenna-core supercomplexes into the repair-compatible reaction center 47 (RC47) complex. Our research also identifies new PSII phosphoproteins with potential roles in PSII mobilization for repair. However, several key questions remain, including the roles of individual phosphosites in disassembly, the mechanisms by which PSII is mobilized for repair, and the structural basis of PSII repair. We hypothesize that protein phosphorylation and oxidative protein modifications drive distinct disassembly and repair steps and that specialized accessory proteins provide the structural basis for repair. The proposed research will test this hypothesis in the model plants Arabidopsis thaliana and Nicotiana tabacum. Our approach includes analyzing PSII disassembly and mobilization in mutants with targeted core phosphosite mutations and solving the structures of repair intermediates by cryo-electron microscopy from a core hyperphosphorylating mutant that overaccumulates disassembled complexes. Collectively, these analyses will elucidate the molecular mechanisms underlying plant PSII repair. Photoinhibition resulting from PSII photodamage is a key limiting factor that prevents plants from achieving their full photosynthetic potential and can, depending on the species, reduce daily carbon uptake by 6-30% under field conditions. With the PSII repair cycle emerging as a new frontier for improving photosynthesis, developing PSII variants with enhanced light tolerance or an accelerated repair cycle represents a promising strategy. The proposed research will provide critical mechanistic insights to advance these goals.

Photosynthesis by plants, algae, and certain bacteria capture light energy and convert it to chemical energy. To accomplish this, two photosystems operate in concert to harvest light energy and drive the primary light-driven electron transport reactions of photosynthesis, among which photosystem II (PSII) is particularly vulnerable to light-induced damage. This project seeks to elucidate how post-translational modifications promote the disassembly and repair of PSII and the structural basis of the PSII repair process. The reaction center protein D1, located at the core of PSII, is the primary target of photodamage. To maintain photosynthetic efficiency, a repair cycle replaces the damaged D1 subunit with a newly synthesized copy, but the mechanism by which the large PSII antenna-core supercomplexes disassemble for repair has remained unclear. Our recent research reveals a role for protein phosphorylation and oxidative protein modifications in facilitating the disassembly of PSII antenna-core supercomplexes into the repair-compatible reaction center 47 (RC47) complex. Our research also identifies new PSII phosphoproteins with potential roles in PSII mobilization for repair. However, several key questions remain, including the roles of individual phosphosites in disassembly, the mechanisms by which PSII is mobilized for repair, and the structural basis of PSII repair. We hypothesize that protein phosphorylation and oxidative protein modifications drive distinct disassembly and repair steps and that specialized accessory proteins provide the structural basis for repair. The proposed research will test this hypothesis in the model plants Arabidopsis thaliana and Nicotiana tabacum. Our approach includes analyzing PSII disassembly and mobilization in mutants with targeted core phosphosite mutations and solving the structures of repair intermediates by cryo-electron microscopy from a core hyperphosphorylating mutant that overaccumulates disassembled complexes. Collectively, these analyses will elucidate the molecular mechanisms underlying plant PSII repair. Photoinhibition resulting from PSII photodamage is a key limiting factor that prevents plants from achieving their full photosynthetic potential and can, depending on the species, reduce daily carbon uptake by 6-30% under field conditions. With the PSII repair cycle emerging as a new frontier for improving photosynthesis, developing PSII variants with enhanced light tolerance or an accelerated repair cycle represents a promising strategy. The proposed research will provide critical mechanistic insights to advance these goals.