Sequence-specific transcription factor which is part of a developmental regulatory system that provides cells with specific positional identities on the anterior-posterior axis (By similarity). Plays a role in early embryonic development. Expressed both maternally and zygotically. Detected in every cell of early cleavage embryos through to gastrulae. From around 6 hours post-fertilization (hpf) through to early somitogenesis, expressed along the entire anterior to posterior length of the gastrula. At 19 hpf, expression is up-regulated in the developing tail bud and it becomes restricted to the tail bud by 24 hpf. By 40 hpf, expression is further restricted within the tail bud, possibly to the developing vertebrae. No expression at 72 hpf. Morpholino knockdown of the protein results in a biphasic developmental delay characterized by a reduced body size with 22-23 somites by 24 hpf; the first delay occurs before gastrulation and the second during late tail bud development. Belongs to the Abd-B homeobox family.