Fig. 7. Subfunctionalisation of amphioxus Hairy genes after duplication. (A) Summary of Amphi-Hairy gene expression during amphioxus embryogenesis in a dorsal flattened view of an idealised half amphioxus embryo. The four main embryonic tubes are indicated [from dorsal (D) to ventral (V): nerve cord (N), notochord (nt), paraxial mesoderm (pM), gut (g)]. Each Amphi-Hairy gene expression is indicated by color code and line patterns. The summation of Amphi-hairyA to Amphi-hairyD expression mimics that of the single (mouse) or the two (chicken, frog) Hairy genes. (B) Schematic representation of representative enhancers deduced for Amphi-Hairy before gene duplication in the amphioxus lineage. After duplication, specific enhancers were maintained in each copy of Amphi-hairyA to Amphi-hairyF. end1-3, distinct anteroposterior regions of the endoderm; NT1-4, distinct anteroposterior regions of the neural tube; nt, notochord; PSM, presomitic mesoderm.