Characterization of ddx4 and dnd Homologs in Snakeskin Gourami (Trichopodus pectoralis) and Their Expression Levels during Larval Development and in Gonads of Males and Females

SIMPLE SUMMARY: Gene markers that are specific to germ cells are needed for the development of reproductive biotechnologies for fish. To provide valuable molecular information on ddx4 and dnd, which can be applied for further monosex production in snakeskin gourami (Trichopodus pectoralis), this study cloned and characterized ddx4 (ddx4) and dnd (dnd1) homologs and described their temporal expressions in snakeskin gourami (Trichopodus pectoralis). The expressions of ddx4 and dnd1 mRNAs were detectable only in the gonads, particularly in germ cells. The expression of ddx4 was high during early larval development and decreased with increasing developmental age, whereas the expression of dnd1 increased with developmental age. In adult fish, the expression levels of ddx4 and dnd1 were higher in the ovary than in the testis. ABSTRACT: The purpose of this study was to clone and characterize ddx4 and dnd1 homologs in snakeskin gourami (Trichopodus pectoralis) and to determine their expression levels during larval development and in the gonads of males and females. Both cDNAs contained predicted regions that shared consensus motifs with the ddx4 family in teleosts and the dnd family in vertebrates. Phylogenetic tree construction analysis confirmed that these two genes were clustered in the families of teleosts. Both ddx4 and dnd1 mRNAs were detectable only in the gonads, particularly in germ cells. These two genes were expressed during early larval development. The expression of ddx4 was high during early larval development and decreased with increasing developmental age, whereas dnd1 expression increased with developmental age. In adult fish, the expression levels of both genes were higher in the ovary than in the testis. Overall, these findings provide valuable molecular information on ddx4 and dnd, and can be applied in future reproductive biological studies relating to sex dimorphism in snakeskin gourami.