(A) Sequence homogeneity alignment of each subunit of PSII between P. purpureum (Pp) and C. caldarium (Cc) indicates that most of the subunits are highly conserved. (B) Maximum likelihood (ML) phylogenetic analysis of cyanobacteria, red algae, diatom, green algae, and higher plants based on CP47 (PsbB) protein of PSII. The PSII structures of all the analyzed organisms have been resolved (PDB ID: 6KAD, 5XNM, 5MDX, 1VYK, 6AE9, 4YUU, 5OJ3, 5ZZN, 6JLL, etc.). CP47 of Gloeobacter violaceus is introduced as the outgroup. The software is Mega v5.05 and amino acid substitution model is Jones–Taylor–Thornton model. Bootstrap 1000 is used to compute the consensus tree, and computed distance 0.05 is labeled on the bottom left corner. Red algae Pp and Cc, marked with red rectangle, are more closely related than other phyla, such as cyanobacteria, diatom, green algae, and higher plants. (C) Sequence alignment of the N-terminal CP43 subunit of PSIIs of Pp and Cc.