A/P axis: Hox genes
Regionalized central nervous system otd, ems, Hox
segmentation hairy, engrailed, Notch
Regionalized gut ParaHox
circulatory pump tinman/NK2.5
The possible features of the common bilaterian ancestor are deduced from the conservation of genes and their developmental functions between arthropods (Drosophila) and vertebrates (mouse). (top) Patterning of the D/V axis may have been controled by ancestral genes of the short gastrulation (sog )/chordin and TGF-b families. The A/P axis was probably subdivided by nested, overlapping domains of Hox gene expression. (middle) Different tissue layers were regionally patterned along the A/P axis, including the gut (ParaHoxgenes) and the nervous system (otd, ems, Hox). Segmentation may have evolved under the regulation of ancestral hairy, engrailed, and Notch genes. (bottom) Primitive versions of a photoreceptor organ, a circulatory pump, and a body wall outgrowth might have been present in the bilaterian ancestor, under the regulatory control of the ancestral Pax6, tinman, and Dll genes, respectively.
Was this article helpful?