Evolutionary history of two divergent Dmrt1 genes reveals two rounds of polyploidy origins in gibel carp.

Polyploidy lineages, despite very rare in vertebrates, have been proposed to play significant role in speciation and evolutionary success, but the occurrence history and consequences are still largely unknown. In this study, we used the conserved Dmrt1 to analyze polyploidy occurrence and evolutionary process in polyploid gibel carp. We identified two divergent Dmrt1 genes and respectively localized the two genes on three homologous chromosomes. Subsequently, the corresponding full-length cDNAs and genomic sequences of Dmrt1 genes were also characterized from the closely related species including Carassius auratus auratus and Cyprinus carpio, and their two Dmrt1 genes were respectively localized on two homologous chromosomes. Significantly, the evolutionary relationship analyses among cDNA and genomic DNA sequences of these Dmrt1 genes revealed two rounds of polyploidy origins in the gibel carp: an early polyploidy might result in an common tetraploid ancestor of Carassius auratus gibelio, Carassius auratus auratus and Cyprinus carpio before 18.49 million years ago (Mya), and an late polyploidy might occur from evolutionary branch of Carassius auratus at around 0.51 Mya, which lead to the occurrence of the hexaploid gibel carp. Therefore, this study provides clear genetic evidence for understanding occurrence time and historical process of polyploidy in polyploid vertebrates.