Abstract:In order to understand the function of vasa gene in the development of germ line and the reproduction of primordial germ cells in Ovomermis sinensis, the full-length cDNA sequence of Os-vasa was cloned from the mermithid by rapid amplification of cDNA end (RACE) methods. The full length of Os-vasa cDNA is 3 053 bp, encoding 813 amino acids. The putative amino acid sequence possesses all nine conserved motifs of the DEAD-box family. High identity of VASA in amino acid sequence (more than 58%) was observed between O.sinensis and the other organisms through blast analysis, indicating that the cloned cDNA belonged to the subfamily of VASA. Expression of Os-vasa was detected by reverse transcription PCR (RT-PCR) and real time PCR. The results showed that the Os-vasa gene specifically expressed in the gonads of both male and female, and there was no expression in other body parts, such as head, tail and body wall. The expression of Os-vasa in the early development stage of gonads was much higher than those in other development stages. Moreover, the transcription of vasa mRNA was relatively high in embryo stage, suggesting that vasa gene might be a maternal factor for the embryogenesis and plays an important role in the early embryo development.