Fig. 7.

Organization and distribution of conserved retinoic acid response elements (RAREs) in the amphioxus CYP26 cluster. (a) Schematic representation of the experimentally verified amphioxus (Branchiostoma lanceolatum) CYP26-1, CYP26-2, and CYP26-3 gene sequences, including the 5′ and 3′ untranslated regions (UTRs) and the exons of the coding region, as well as of the corresponding scaffolds of the B. lanceolatum genome that cover the complete CYP26 cluster and thus also include intronic and intergenic regions. The names of the B. lanceolatum genome scaffolds are indicated, as is their orientation relative to the CYP26 cluster (+/− strand). (b) Distribution of conserved amphioxus RAREs in the B. lanceolatum CYP26 cluster. The orientation of each RARE is indicated relative to the CYP26 cluster (+/−). RAREs recognized and bound by the B. lanceolatum RAR/RXR heterodimer in vitro are indicated in black, RAREs that do not associate with the B. lanceolatum RAR/RXR heterodimer in vitro are shown in grey. The RARE sequences are given in Additional file 4 and the in vitro assays are shown in Fig. 8