Neighbor-joining phylogeny inferred from aligned amino acid sequences of ARDOs. ARDOs forming a monophyletic group with previously validated and clustered ARDOs are considered to be of the same group. Bootstrap values equal to or greater than 50% are shown, and the scale bar represents the number of substitutions per site. For the functionally validated ARDOs, the accession number is shown directly next to the dioxygenase followed by its isolation source. ARDOs shown in boxed lines exhibited distinctive characteristics and are referred to in the text.