Light‐dependent N‐terminal phosphorylation of LHCSR3 and LHCB4 are interlinked in Chlamydomonas reinhardtii

Summary Phosphorylation dynamics of LHCSR 3 were investigated in Chlamydomonas reinhardtii by quantitative proteomics and genetic engineering. LHCSR 3 protein expression and phosphorylation were induced in high light. Our data revealed synergistic and dynamic N‐terminal LHCSR 3 phosphorylation. Phosphorylated and nonphosphorylated LHCSR 3 associated with PSII ‐ LHCII supercomplexes. The phosphorylation status of LHCB 4 was closely linked to the phosphorylation of multiple sites at the N‐terminus of LHCSR 3, indicating that LHCSR 3 phosphorylation may operate as a molecular switch modulating LHCB 4 phosphorylation, which in turn is important for PSII ‐ LHCII disassembly. Notably, LHCSR 3 phosphorylation diminished under prolonged high light, which coincided with onset of CEF . Hierarchical clustering of significantly altered proteins revealed similar expression profiles of LHCSR 3, CRX , and FNR . This finding indicated the existence of a functional link between LHCSR 3 protein abundance and phosphorylation, photosynthetic electron flow, and the oxidative stress response.