The Vasa gene encodes a protein of DEAD-box family that is essential for PGCs proliferation.In this study,we characterized the cDNA of Vasa and researched its expression in the reproductive cycle of Cynoglossus semilaevis through RACE and RT-PCR technology,aiming to clarify its function in gametogenesis of fishes.The length ef Vasa gene is 2 602 bp and this gene encodes a protein of 722 amino acids.The dudced amino acid sequence contains 8 conserved motifs of DEAD-box family protein,5 RGG repeats and 10 RG repeats in N-terminal region.Comparisons of the deduced amino acid sequence with those of other vertebrates and invertebrates revealed the highest homology(91%)with Thunnus orientalis. Vasa was strongly expressed in gonad and little expressed in heart.In the reproductive cycle,the transcript level of Vasa gene in the primary yolk stage and tertiary yolk stage is higher than peri-nucleolus stage and atretic follicles in ovary.The transcript level of spermatogenesis stage is obviously higher than that of spermatocyte stage and spermiation stage.These results suggest that Vasa gene may play an important role in spermatogenesis and oogenesis during reproductive cycle.