Fig. 1.

Presence/absence of methylation-related genes across cnidarians. The tree was assembled from published trees (Kayal et al. 2018; Yahalomi et al. 2020). Black and white squares represent the presence and absence of each gene, respectively. Predicted MBD proteins were characterized as part of our phylogenetic analyses. According to this tree 1) DNMT1, DNMT2/TRDMT1, and MBD4/MeCP2 would have been lost in an ancestor of Myxozoa (red circle); 2) DNMT3 and TET proteins would have been lost in a common ancestor of Myxozoa and Polypodium hydriforme (orange circle); 3) MBD1/2/3 would have been lost in a common ancestor of Myxosporea (black circle); and 4) METLL4 would have been lost in an ancestor of P. hydriforme and in an ancestor of Buddenbrockia plumatellae. It should be noted, however, that only transcriptomic data are available for P. hydriforme, and that only sparse EST data are available for Malacosporea (asterisks represent species with only transcriptomic or EST data), and thus it is possible that all relevant genes may be present in these species and that DNMTs, MBDs, and TETs would have been lost in the branch preceding the diversification of Myxosporea. Question marks indicate uncertainties regarding the absence of genes in that species due to incomplete genome data. The “2” indicates that the gene encoding MBD1/2/3 is duplicated in Dendronephthya gigantea. The last column corresponds to the presence and absence of DNA cytosine methylation in each species (or in another species of the same genus); the absence of a square indicates that neither a methylome nor the absence thereof has been reported. Cytosine methylation data were obtained from Zemach et al. (2010) (Nematostella vectensis), Hassel et al. (2010) (Hydra), Putnam et al. (2016) (Pocillopora damicornis), Dixon et al. (2016) (Acropora millepora), Liew et al. (2018) (Stylophora pistillata), Li et al. (2018) (Exaiptasia pallida), and the current study (Ceratonova shasta and Henneguya salminicola).