Activities of Amphioxus GH-Like Protein in Osmoregulation: Insight into Origin of Vertebrate GH Family

Figure 8

A proposed model for the evolution of GH/PRL family. (a) Ancestral GH/GHR system already emerged in the basal chordate, and PRL/PRLR originated with the advent of Gnathostomata. (b) The ancestral gene, like amphioxus GHl gene, generated two genes by gene duplication early in vertebrate evolution. One of the resulting genes evolved directly into GH gene in modern Gnathostomata, while the other gene evolved into PRL gene, possibly due to adaptation of FW habitats, by genetic innovations and/or mutation after split of agnathan/Gnathostomata.

(a)

(b)