Nuclear hormone receptors (NHRs) are transcription factors which are important for many physiological functions, such as development, cellular differentiation, metabolism, and defense against xenobiotics in a variety of animal.The genome of Caenorhabditis elegans encodes 284 nuclear receptor (NR) genes.Among these 284 NR genes, 15 genes are conserved among the Metazoa.Until now, the function and the expression pattern of eight conserved NR genes remain uncharacterized in C.elegans.A typical molecular architecture of NHRs includes a conserved N-terminal DNA-binding domain (DBD), which composed of two zinc fingers and a more variable C-terminal ligand binding domain (LBD), which composed of 11 to 12 helixes, underlies NR signaling capabilities.Most NHRs can be found in vertebrates and belongs to six major subfamilies that are evolutionarily conserved throughout the Metazoan.