Phylogenetic tree and a proposed evolutionary scheme of ABCB family. Above: the proposed events in the evolution of the ABCB family. a, putative full transporter formation process and divergence of the ABCB transporter with gain and loss of introns, the colored vertical bars in the NBD region represent conserved introns; b, divergence of the ABCB transporter gene to give rise to each group. Below: part of tree from Figure 1 with introns locations of NBDs, the asterisk represents the root in the midpoint. Each group was marked as a line with the same color to the pane in b; genes that have a Paramecium ortholog were marked with a blue ellipse.