Abstract
In recent years, some common themes in the development of sex-specific traits in different animal lineages have started to emerge since the discovery of the Dmrt (doublesex-mab3-related transcription factor gene) genes. Bivalves are characterized by a diversity of sexual systems, including simultaneous hermaphroditism, sequential hermaphroditism, and strict gonochorism. However, to date, no research has focused on the genome-wide characterization and analysis of Dmrt genes in bivalves. In this study, the identification and analysis of Dmrt genes in 15 bivalves were performed using bioinformatics methods. A total of 55 Dmrt genes were retrieved in the studied bivalve genomes. The number of Dmrt genes in different species ranged from 3 to 5. The phylogenetic tree showed that Dmrt genes in bivalves can be subdivided into 5 classes: the Dmrt2-like class, Dmrt3-like class, Dmrt4/5-like class, Dsx-like class, and scallop-specific Dmrt class. The Ka/Ks ratios suggested that all Dmrt classes underwent purifying selection pressure. Furthermore, the spatiotemporal expression of Dmrt genes in four bivalve species suggested that different Dmrt genes may have different functions, and scallop-specific Dmrt genes may play a key role in sex determination/differentiation. In general, this study provides a molecular basis for in-depth examination of the functions of Dmrt genes and phylogenomic analyses in bivalves.