A, Detection of the PSII core subunit D2 and FtsHi4 by immunoblotting on two-dimensional gel electrophoresis. Membrane samples were solubilized with DM and separated in the first dimension on a blue native gel followed by SDS-PAGE in the second dimension. D2 and FtsHi4 proteins were detected using appropriate antibodies. The separated complexes are designated as: I, PSII supercomplexes; II, monomeric PSI and dimeric PSII; III, monomeric PSII; IV, dimeric cytochrome b6/f dimmer; V, trimeric LHCII; and VI, monomeric LHCII. B, Immunoblot analyses for the accumulation of D2, PsbO and FtsHi4 PSII proteins in wild-type and mutant ovules from heterozygous ftshi4-1 mutant plants. The thylakoid membrane proteins were fractionated by SDS-urea-PAGE, and the blots were probed using antibodies raised against D2, PsbO, or FtsHi4.