Transcription factor, involved in posterior embryonic patterning, morphogenetic movements of the posterior hypodermis, and cell fate specification (PubMed:21408209, PubMed:10781051, PubMed:16824957, PubMed:20824072). Binds to the 5'-TAGT-3' motif in regulatory elements of genes, including Meis protein psa-3 and microRNA mir-57 (PubMed:16824957, PubMed:20824072). Involved in a negative regulatory loop with mir-57 to specify posterior cell identities (PubMed:20824072). Required for asymmetric division of the T hypodermal cell, acting via the regulation of asymmetric expression of psa-3 in cooperation with ceh-20 and the Wnt-MAPK pathway (PubMed:16824957). Involved in the regulation of the onset of non-apoptotic cell death in the linker cell, acting together with the Wnt signaling pathway (PubMed:27472063). Involved in promoting embryogenesis, in concert with orphan nuclear receptor nhr-25 (PubMed:15314147). May regulate expression of transcription factor dmd-3 (PubMed:21408209). Interacts with nuclear receptor nhr-25 (PubMed:15314147). Interacts with geminin homolog gmn-1 (PubMed:15811859). Interacts with homeodomain protein ceh-20 (PubMed:16824957). Expressed from the 100-cell stage in posterior progeny of ABp(l/r)pp and ABp(l/r)ap (PubMed:20824072). Expressed in the tail tip cells hyp8-11 throughout larval development in both sexes (PubMed:21408209). Expressed in the linker cell from the L3 larval stage onward (PubMed:27472063). Repressed directly by microRNA mir-57. RNAi-mediated knockdown applied to adults causes posterior morphological abnormalities in their F1 progeny (PubMed:10781051). Knockdown by feeding of dsRNA to stage L1 larvae causes defects in tail tip morphogenesis and reduces expression of dmd-3; both of these phenotypes are exacerbated on a php-3 mutant background (PubMed:21408209). Knockdown represses expression of microRNA mir-57 in the AB cell sublineages (PubMed:20824072). Belongs to the abd-b homeobox family. Intron retention.