Neighbor-joining trees of AtRH (A), CeRH (B), and DmRH (C) proteins and intron positions in the 10 most conserved regions of the catalytic domain for AtRH,CeRH, and DmRH genes. (square brackets) The numbers of introns conserved between the genes in a branch. The bootstrap values for 1000 trials are indicated at each fork. The horizontal bar represents 0.1 substitution per nucleotide. Intron positions in the overall alignments of sequences are as follows: (‖) phase 0 introns; ([) phase 1 introns, and (•) phase 2 introns. Conserved protein regions are named as in Table 1. Conserved intron positions inAtRHs, CeRHs, and DmRHs, betweenAtRHs and CeRHs, AtRH and DmRHs, and CeRHs and DmRHs, as well as between the three organisms, are represented on the scaffold structures at thebottom of (A), (B), and (C). Numbers below the intron position are the positions of introns in base pairs in the considered conserved protein region. (Figure continues on following page.)