Involved in control of cell fate and pattern formation along the anterior-posterior axis, acting mainly in the tail (PubMed:8101474, PubMed:1879361, PubMed:10049576). Required during embryonic and postembryonic development (PubMed:1879361). Essential for the determination of specific neurons, including the PLM touch neurons (PubMed:8101474, PubMed:12835398). Plays a role in neural fate specification in the hermaphrodite-specific neuron (HSN)/PHB neuron lineage, acting in concert with T-box protein tbx-2 and the asymmetric cell division protein ham-1 (PubMed:18505863). Required for male gonadal fate determination, acting in parallel with a WNT/beta-catenin pathway, perhaps by recruiting pop-1 to male-specific gonadal target genes (PubMed:20553900). Involved in development of the hermaphrodite hindgut, and for the response to rectal infection by the coryneform bacterium M.nematophilum (PubMed:19232338). Interacts with the TCF transcription factor pop-1. Expressed throughout postembryonic development and adulthood (at protein level) (PubMed:10049576). In young larvae (10 h posthatching), expressed in five rectal epithelial cells, three left-right pairs of neurons, and four to six bilateral pairs of body-wall muscle cells, in the posterior body region (at protein level) (PubMed:10049576). At the same developmental stage, also expressed in the pair of hermaphrodite-specific neurons (HSN), in the mid-body adjacent to the gonad (at protein level) (PubMed:10049576). In early larvae, expressed in the male tail, and in hermaphrodite Ll stage larvae (0-2.5 hr post-hatching) in the most posterior body region and the tail (PubMed:17574230, PubMed:8101474). Expressed in most if not all somatic cells in the male gonad, with the exception of the linker cell (LC) and distal tip cells (DTCs) and their progenitors (PubMed:20553900). Fails to swell on exposure to the rectal pathogen M.nematophilum, a coryneform bacterium. Belongs to the Abd-B homeobox family.