Fig. 1.

The phylogenetic distribution of PRDM9 and its domain architecture across vertebrates. The inferred PRDM9 status of 432 vertebrate species is shown. Branch lengths were computed based on the TimeTree database. For 28 species not present in the database, we used branch length information from a close evolutionary relative; for 14 species in which we made PRDM9 calls, we were unable to find such a substitute, so they are not represented. Different vertebrate clades are indicated by colored segments, with salmon for mammals, cyan for fish, mustard for amphibians, green for reptiles, and purple for birds. In the inner circle, squares indicate whether PRDM9 is complete (solid black) or incomplete/absent (open black); for species with an uncertain PRDM9 status, no box is shown. The PRDM9 domain architecture of each species is shown with a cartoon, in which the presence of a KRAB domain is indicated in blue, SSXRD in pink, and the SET domain in orange. Green triangles indicate species that only carry PRDM9 orthologs with substitutions at putatively important catalytic residues in the SET domain (see SI Appendix, Table S4). The tree was drawn using itool (https://itol.embl.de/); an interactive version is available at https://itol.embl.de/shared/izabelcavassim.