Relationships within the completed sets of NR superfamily members from humans, C. elegans and Drosophila. A neighbor-joining tree of NR DNA-binding domain sequences was generated using the paupsearch feature of the GCG 10.1 program package (1,000 bootstrap replicates, midpoint rooting); analysis methods are described in detail in Sluder et al. . Significant bootstrap support values are indicated by slashes on the appropriate branches: (/) 50-79%; (//) 80-94%; (///) ≥ 95%; branches also supported by parsimony analysis are marked by dots; subfamilies are boxed. All human (Hs) and Drosophila (Dm) NRs are included, except for the two human NRs that lack a canonical DBD (DAX-1 (NR0B1) and SHP (NR0B2)). The C. elegans (Ce) sequences include all members of the six major metazoan NR subfamilies as well as selected representatives of the major groupings of divergent C. elegans NRs evident in a larger tree containing all the nematode sequences.