Fig. 3

dmrt1bY evolution and regulation in Oryzias latipes. a In the ancestor, the dmrt1 gene existed in a single copy on a pair of autosomes. dmrt1 was then duplicated into dmrt1a and dmrt1b. Later, two TEs inserted upstream of dmrt1b: Izanagi, a DNA/P-element, followed by Rex1, a LINE retrotransposon [98]. After the insertion of these TEs, dmrt1b became the master sex-determining gene dmrt1bY and the chromosome harboring it became the Y chromosome (the gene is absent from the X). b dmrt1bY is expressed during sex determination in the prospective males. Its product triggers sex determination towards the male phenotype. It also binds on its own binding site in Izanagi, down-regulating its own expression. After sex determination and in adults, dmrt1a, the ancestral paralog of dmrt1bY, is expressed. It binds to Izanagi, down-regulating and silencing dmrt1bY once sex determination has occurred. This silencing is also ensured by the binding of Sox5 to a motif encompassed in the Rex1 sequence