Loss‐of‐function of OsSTN8 suppresses the photosystem II core protein phosphorylation and interferes with the photosystem II repair mechanism in rice (Oryza sativa)

Summary STN8 kinase is involved in photosystem II ( PSII ) core protein phosphorylation ( PCPP ). To examine the role of PCPP in PSII repair during high light ( HL ) illumination, we characterized a T – DNA insertional knockout mutant of the rice ( O ryza sativa ) STN 8 gene. In this osstn8 mutant, PCPP was significantly suppressed, and the grana were thin and elongated. Upon HL illumination, PSII was strongly inactivated in the mutants, but the D 1 protein was degraded more slowly than in wild‐type, and mobilization of the PSII supercomplexes from the grana to the stromal lamellae for repair was also suppressed. In addition, higher accumulation of reactive oxygen species and preferential oxidation of PSII reaction center core proteins in thylakoid membranes were observed in the mutants during HL illumination. Taken together, our current data show that the absence of STN 8 is sufficient to abolish PCPP in osstn8 mutants and to produce all of the phenotypes observed in the double mutant of A rabidopsis, indicating the essential role of STN 8‐mediated PCPP in PSII repair.