Conserved, highly similar and similar residues are highlighted in green, yellow and gray, respectively. (A) Sequences are those from the primordial cyanobacterium Gloeobacter violaceus PCC 7421 (NP_923828); cyanobacteria, Prochlorococcus marinus MED4 (CAE19565), Synechococcus sp. PCC 7002 (ACA98109), Synechocystis sp. PCC 6803 (BAA16792), Acaryochloris marina MBIC11017 (ABW27358); red algae, Porphyra purpurea (NP_053814), Bangia fuscopurpurea (AKE98807); green algae, Bathycoccus prasinos (XP_007514179), Ostreococcus tauri (XP_022839105), Chlamydomonas reinhardtii (XP_001691121); the moss Physcomitrella patens (XP_001756877); higher plants, Cucumis sativus (XP_004139926), Arabidopsis thaliana (NP_200633), Nicotiana tobacum (XP_016480530), Hordeum vulgare L. cv. Bonus (BAJ91312), Oryza sativa L. ssp. japonica (XP_015628146). The conserved Ycf54 domain is indicated. The C-terminal 37 aa sequence deleted in the YCF54* mutant is underlined. (B) Sequence alignments showing the conservation of the C-terminal extensions present specifically in green algal and plant Ycf54 proteins. Additional green algal and plant Ycf54 sequences are included, which are from the green alga Coccomyxa subellipsoidea C-169 (XP_005642819); the liverwort Marchantia polymorpha (PTQ33664); higher plants, Brachypodium distachyon (XP_003557990), Zea mays (NP_001131876), Spinacia oleracea (XP_021852323), Vitis vinifera (XP_010650790), Erythranthe guttata (XP_012838088), Ipomoea nil (XP_019188624), Solanum lycopersicum (XP_004240451), Medicago truncatula (XP_013460499), Lotus japonicus (AFK37846). Full-length sequences were used for alignments but for clarity, only the C-terminal extension regions with the residue range indicated, are shown.