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. 2024 Feb 8;43(5):8. doi: 10.1038/s44318-024-00034-3

Figure 9. Meiotic HORMADs encode a variable central chromatin-binding region.

Figure 9

(A) Cartoon of a phylogenetic tree of diverse eukaryotes (a subset of 87 out of 158 species analyzed in this study), with individual domains in meiotic HORMAD proteins noted: HORMA domain beige, PHD domain blue, wHTH domain green, HTH-C domain orange, PWWP yellow and the closure motif grey. Numbers in the HORMA domain field indicate the number of detected meiotic HORMADs in a given genome. Two different shapes are depicted for the wHTH domain, each indicating the number of wHTH domains detected in a single meiotic HORMAD protein. Major eukaryotic groups are color-coded and labeled. See full dataset of 158 species/149 HORMAD proteins in Table EV1. (B) AlphaFold 2 predicted structures of selected meiotic HORMAD CBRs (indicated with a star and in bold text in (A)). All CBRs are shown with PHD domain blue, wHTH green, and HTH-C orange. Strongylocentrotus purpuratus (Uniprot ID A0A7M7T0L9) residues 329–476 (PHD 329–395, wHTH 396–476); Nematostella vectensis (Uniprot ID A7RLI6) residues 280–426 (PHD 280–345, wHTH 346–426); Candida glabrata (Uniprot ID Q6FIP6) residues 319–526 (PHD 319–373, wHTH 374–438, HTH-C 439–526); Schizosaccharomyces pombe (Uniprot ID Q9P7P2) residues 333–480 (PHD 333–388, wHTH 389–480); Encephalitozoon cuniculi (Uniprot ID Q8SWC8) resides 1–142 (full length; PHD 1–61, wHTH 62–142); Rozella allomycis (Uniprot ID A0A075AU51) residues 399–551 (PHD 399–454, wHTH 455–551); Acanthamoeba castellanii (Uniprot ID L8H1D9) residues 246–309 (wHTH 1) and 335–394 (wHTH 2); Mantamonas sphyraenae (ID see Table EV1) residues 254–340 (wHTH 1) and 3787–465 (wHTH 2); Trypanosome brucei (Uniprot ID Q38B55) residues 292-406 (wHTH); Plasmodium falciparum (Uniprot ID Q8IEM0) residues 973–1053 (wHTH 1) and 1214–1287 (wHTH 2); A. thaliana ASY1 (Uniprot ID F4HRV8) residues 297–362 (wHTH 1) and 388–471 (wHTH 2); Chlamydomonas reinhardtii (Uniprot ID A0A2K3DBA0) residues 443–516 (wHTH). Of note: C. reinhardtii wHTH is most similar to A. thaliana wHTH 1, while T. brucei wHTH is more similar to other wHTH 2 domains. See Fig. EV5 for sequence alignments. (C) Reconstruction of the evolution of the CBR of meiotic HORMAD protein throughout the eukaryotic tree of life. Six key events can be discerned: (I) replacement of the N-terminal wHTH domain in the ancestor of fungi and animals (Opisthokonta) with a PHD domain; (II) loss of the PHD-wHTH configuration in a number of animal lineages (i.e., Vertebrata and the nematode class Chromadorea); (III) C-terminal extension (HTH-C) of the wHTH specific for Saccharomycetes; (IV) differential loss of one of the two wHTH domains in various clades within the supergroups SAR and Archaeplastida; (V) independent gains of PWWP-like domains in Chloroplastida and Cryptista; (VI) unclear (inferred) ancestral presence of a single or double wHTH configuration in the Last Eukaryotic Common Ancestor (LECA). Source data are available online for this figure.