Caudal (cad) is one of a number of transcription factors controlling segmentation of the embryo. Further transcriptional regulation via a 5' flanking region containing DNA replication-related elements (DRE) and by dref also regulated by trh and tgo via the CNS midline element. Alongside Bicoid (bcd), caudal forms concentration gradients down the anterior-posterior (A-P) axis providing positional information and subsequent induction of the gap genes. Plays a role in gastrulation/germ band extension, hindgut morphogenesis, positive regulation of cell proliferation, genital disk development and pattern formation. Acts as a key regulator of the Hox gene network and activates transcription via the downstream core promoter element (DPE) relative to the TATA box. Plays a role in the establishment of the hindgut and in the invagination of the hindgut primordium during gastrulation. These effects on the gut are achieved by acting combinatorially at the posterior of the embryo to activate transcription of different targets including fog, fkh and wg. Caudal is involved in regulation of proliferation through transactivation of the E2F gene. Postembryonically its function is mostly restricted to the intestine where it regulates antimicrobial peptide (AMP) levels preserving the normal gut flora. Maternally localized in an anteroposterior gradient in the syncytial blastoderm. Also expressed in the pole cells. Zygotically localized in the primordia of the terminal abdominal segment, the hindgut and in the posterior midgut rudiment. Expressed in the gut, the gonads and parts of the genital disks of third instar larvae (at protein level). Expressed both maternally and zygotically. Belongs to the Caudal homeobox family.