Evolutionary expansion and conservation of kinases and respective substrates. (A) Evolutionary conservation of substrates of kinase groups: CIs for each kinase group defined in PhosphoSitePlus  were calculated using the same method as the CIs of phosphomotifs (see the section of the definition of phosphomotif CIs). See also Data5-1 in Additional file 5. (B) Evolutionary expansions of kinase groups: 371 kinases were classified into nine kinase groups and were extracted from PhosphoSitePlus and KEGG BRITE databases. Orthologs of the kinases in the genomes hsa, mmu, dre, dme, and cel were assigned by the KEGG SSDB homology database. See also Additional file 6. Fractions of kinase groups for each genome obtained from KEGG SSDB were calculated. In addition, the fraction that was calculated for the kinases classified in WormBase used in the study by Lehmann et al. is indicated by an asterisk [28,29]. The blue line indicates the number of kinase genes. The assignment of kinase groups was performed using PhosphoSitePlus [13,14]. hsa, Homo sapiens; mmu, Mus musculus; dre, Danio rerio; dme, Drosophila melanogaster; cel, Caenorhabditis elegans.