Sequence conservation of Bug22p in eukaryotes and positions that distinguish ciliary versus nonciliary species. The ClustalW alignment of 58 Bug22p sequences, representative of all the clades of eukaryotic species in which it can be found, was visualized using Boxshade and illustrates the strong conservation of the Bug22p protein through evolution. Careful examination of the divergences at seven specific positions (amino acids 30, 38, 45, 55, 66, 67, and 111 according to the numbering of the Homo sapiens Bug22p sequence) revealed that species having cilia or centrioles in at least some stage of their life cycle have a consensus at these positions (denoted in purple) that dramatically differs from the consensus found in plants (denoted in green), as displayed at the bottom of the figure. Note that both the moss Physcomitrella patens and the fern Selaginella moellendorfii (in the middle of the alignment), which both have several Bug22 genes in their genomes and are plants with occurrence of flagellated cells in their life cycles, display a patchwork of the plant consensus and the ciliary consensus at these positions. In addition, the occurrence of a BUG22 gene with ciliary consensus in the genome of Chlorella vulgaris, harboring a centriole that never develops a cilium (39), suggests that Bug22p has a centriolar function. The species studied and the accession numbers of the proteins are as follows: Aa, Aedes Aegypti XP_001663334.1; At, Arabidopsis thaliana AAG51069.1; Am, Apis mellifera XP_395824.1; Bd, Batrachochytrium dendrobaditis jgi ∣Batde5∣ 32931; Bm, Bombyx mori NP_001040392.1; Brm, Brugia malayi XP_001894987.1; Bt, Bos taurus NP_032213.2; Cca, Capitella capitata jgi ∣Capca1∣77038; Ccl, Citrus clementina EST:FC926856.1, GI:218791863; Ci, Ciona-intestinalis XP_002131975.1; Ce, Caenorhabditis elegans NP_871706.1; Cv, Chlorella vulgaris jgi ∣Chlvu1∣29644∣e; Cr, Chlamydomonas reinhardtii XP_001692489; Cp, Carica papaya EST: EX271746.1, GI:186814042; Cq, Culex quinquefasciatus XP_001869024.1; Dm, Drosophila melanogaster NP_609402.1; Dr, Danio rerio NP_957105.1; Ee, Euphorbia esula EST: DV114861.1; Eg, Elaeis guineensis ACF06559; Gg, Gallus gallus NP_001005833.1; Gh, Gossypium hirsutum EST: EX168390.1 GI:164311590; Gl, Giardia lamblia XP_001708694.1; Gm, Glycine max gb:ACU16157.1; Hm, Hydra magnipapillata XP_002163101.1; Hs, Homo sapiens NP_037374.1; Lb, Leishmania_braziliensis XP_001564754.1; Lj, Lotus japonicus EST: GO028159.1, GI:223439164; Ls, Lactuca serriola EST:BQ986870.1, GI:22404395; Me, Manihot esculenta EST:DV448997; Mg, Mimulus guttatus EST:GR148812.1, GI:238398755; Mm, Mus musculus NP_032213.2; Mp, Micromonas_pusilla jgi ∣MicpuC2∣70275∣AZW; Mt, Medicago trunculata ACJ85502.1; Ng, Naeglaeria gruberi JGI Protein ID: 81674; Ot_1p, Oxytricha trifallax OXADaaa05e09; Ot_2p, Oxytricha trifallax OXAEaaf21g04; Ot_3p, Oxytricha trifallax OXAEaaa06d08; Pf, Plasmodium falciparum XP_001351642.1; Pp_1, Physcomitrella patens XP_001775608.1; Pp_2, Physcomitrella patens XP_001760380.1; Pp_3, Physcomitrella patens XP_001784194.1; Ps, Picea sitchensis ABK26040.1; Pt, Paramecium teraurelia (this article); Ptr, Populus trichocarpa XP_002304809.1; Sb, Sorghum bicolor XP_002460501.1; Sm_1, Selaginella moellendorfii jgi ∣Selmo1∣172529; Sm_2, Selaginella moellendorfii jgi ∣Selmo1∣96514; Sm_3, Selaginella moellendorfii jgi ∣Selmo1∣130480; Sm_4, Selaginella moellendorfii jgi ∣Selmo1∣117290; Ta, Trichophlax adherens jgi ∣Triad1∣ 23937; Tb, Trypanosoma brucei XP_822473.1; Tc, Tribolium castaneum XP_975505.1; Tg, Toxoplasma gondii XP_002364709.1; Tt, Tetrahymena thermophila XP_001007313.2; Tp, Thalassiosira pseudonana XP_002286290.1; Vv_1p, Vitis vinifera XP_002268386.1; Vv_2p, Vitis vinifera XP_002265223.1; Xp, Xenopus tropicalis NP_001004835.1; Zm, Zea mays NP_001148848.1.