Fig. 7.

Comparisons between amphioxus and Xenopus. a Comparisons of organizer formation and organizer gene regulatory networks (GRNs) between amphioxus (left) and Xenopus (right). GRNs in the head organizer of Xenopus are shown with a magenta circle. White boxes, CRMs of each gene; gray box, CRMs of amphioxus otx, which have not been identified yet; dotted lines, suggested regulation [26]. b Comparisons of expression domains of transcription factors (otx, lim1, gsc, and brachyury) in the dorsal endoderm and the dorsal mesoderm between amphioxus (a–c) and Xenopus (d–f). Colored bars represent expression domains of genes at the early gastrula stage (a,d), the late gastrula stage (b,e) and the late neurula stage (c,f) with anterior to the left, as indicated. The head organizer region and regulatory interactions between transcription factors are indicated in the late gastrula stage in Xenopus