ASHS 2025 Conference

Photosynthesis, the process by which light is converted into chemical energy, occurs in chloroplasts and involves two photosystems (PS II and PS I) connected by the cytochrome b6f complex. PS II is responsible for water splitting in oxygenic photosynthesis and is composed of a dimeric core and peripheral antennae. These antennae regulate excitation pressure under varying light conditions, preventing damage to PS II. In high-light environments, dissociation of the antennae is crucial for optimizing light harvesting and enabling self-repair of PS II. Phosphorylation of core proteins, particularly at the Thr2 residue in PsbA (D1) and PsbD (D2), plays a key role in antenna regulation and PS II repair. However, the mechanisms underlying phosphorylation-dependent disassembly of PS II are not well understood. In this study, we generated mutated PsbA and PsbD genes with alanine substitutions at the Thr2 phosphorylation site. These mutated genes were introduced into the chloroplast genome via particle bombardment, and homologous recombination was used to replace the native genes. Characterizing plants with these mutations will provide insight into the role of phosphorylation in the disassembly of PS II, a process crucial for light-harvesting efficiency and repair. This work aims to enhance our understanding of photosynthetic regulation and inform strategies for improving crop efficiency.