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.