Figure 1
Phylogenetic relationship of the S8A protease gene subfamily. (a) Maximum likelihood unrooted phylogenetic tree of the S8A subfamily from representative Archaea, Bacteria and eukaryote species was constructed with IQ-TREE (model: LG + R10, predicted by Modelfinder) using an ultrafast bootstrap approximation (100,000 bootstrap replicates). Colored domains display eight different clusters in the S8A subfamily. The domains with a continuous line indicate resolved clusters, while domains with dotted lines represent undefined clusters. The colored circles at the top left represent the species composition of individual clusters. The plant subtilases (SBT1-5) apparently originated from bacterial subtilases (red branches in in paraphyletic divergences) through a single HGT. (b) Phylogenetic analysis of plant subtilases using an extended taxon sampling of bacterial subtilases to search for a bacterial sister group to the plant subtilases was constructed by Maximum Likelihood using 500 bootstrap replicates (model: WAG + F + R7, predicted by Modelfinder). Plant subtilases are monophyletic with a clade of bacterial sequences derived from four phyla (Proteobacteria (only Gammaproteobacteria and Betaproteobacteria), Chloroflexi, Actinobacteria and Firmicutes). The streptophyte algal sequences from Mesotaenium endlicherianum, Coleochaete scutata and “Spirotaenia sp.” diverge paraphyletically from the common ancestor of the plant subtilases with “Spirotaenia sp.” in sister position to embryophytes (the detailed tree with all taxon and species names is shown as Supplementary Fig. S1). Some bacterial S8 genes from the phylogenetic tree of the S8 cluster 1 (a) were selected as an outgroup.
