Fig. 6.

Secondary structures of basal metazoan TRs. (A) Evolutionary relationship of basal metazoan phyla and classes with TR identified. The numbers of TRs identified in this study for each class are indicated. An asterisk denotes the classes for which the TR secondary structure of a representative species is shown in B–D. Fungi represents the outgroup in the phylogenetic tree. (B–D) Representative TR secondary structures determined by phylogenetic comparative sequence analyses are shown for Acropora digitifera (digitate coral) from phylum cnidaria (B), Trichoplax adhaerens (flat animal) from phylum placozoa (C), and Amphimedon queenslandica (common sponge) from phylum porifera (D). The conserved TR structural domains are shaded. Universal covariations (thick lines), invariant residues, and residues with >80% conservation are based on the sequence alignment of 55 previously identified animal TRs and 82 novel metazoan TRs identified in this study. Group-specific covariations are indicated and based on the sequence alignment of TRs from individual groups including 26 cnidaria, 1 placozoa, and 3 porifera species.