Immunoblot analysis was performed as described previously (Fang et al., 2019) . For protein extraction, leaf samples were ground into powder in liquid nitrogen and homogenized in extraction buffer (100 mM HEPES, pH 7.5; 5 mM EDTA; 5 mM EGTA; 10 mM Na 3 VO 4 ; 10 mM NaF; 50 mM b-glycerophosphate; 1 mM phenylmethylsulphonyl fluoride; 10% [v/v] glycerol; 7.5% [w/v] polyvinylpolypyrrolidone; and 0.2% [v/v] b-mercaptoethanol), followed by centrifugation at 13,000 g for 20 min. After adjusting the concentration to the same level, proteins were then mixed with 53 loading buffer (125 mM Tris-HCl, pH 6.8; 5% [w/v] SDS; 25% [v/v] glycerol; 25% [v/v] b-mercaptoethanol; 3.13 mg bromophenol blue/5 mL buffer) and heated at 95°C for 10 min. SDSpolyacrylamide gel (12% [w/v]) electrophoresis (SDS-PAGE) was performed to separate the protein extracts.
For VDE and PsbS detection, antibodies specific to the VDE and PsbS proteins (Agrisera) were used, followed by incubation with a goat antirabbit HRP-linked antibody (Cell Signaling Technology 7074). For HY5 detection, antibodies specific to HY5 proteins (Shanghai Jiayuan Bio.) were used, followed by incubation with a goat antirabbit HRP-linked antibody (Cell Signaling Technology 7074). To test its mobility, a mouse monoclonal antibody recognizing HA (Pierce 26183) was used, followed by incubation with a goat antimouse IgG antibody (Millipore, AP124P).
For VDE and PsbS detection, antibodies specific to the VDE and PsbS proteins (Agrisera) were used, followed by incubation with a goat antirabbit HRP-linked antibody (Cell Signaling Technology 7074). For HY5 detection, antibodies specific to HY5 proteins (Shanghai Jiayuan Bio.) were used, followed by incubation with a goat antirabbit HRP-linked antibody (Cell Signaling Technology 7074). To test its mobility, a mouse monoclonal antibody recognizing HA (Pierce 26183) was used, followed by incubation with a goat antimouse IgG antibody (Millipore, AP124P).