Abstract: Diptericin gene is a member of the antimicrobial peptide family, and plays a key role in insect innate immune system. In this study, a cDNA of 410 bp encoding for a diptericin was cloned from housefly (Musca domestica) by RACE based on dbEST information, which contains a 300 bp open reading frame (ORF) and was named Md-Diptericin (MdDpt) with the GenBank accession no. FJ794602. The C-terminal of the deduced peptide consists of a glycine-rich domain, while the N-terminal consists of a proline-rich domain. The result of sequence alignment analysis showed that this gene shares 74% identity with Stomoxys calcitrans. In addition, the phylogenetic analysis also indicated that the diptericin from housefly was in the same branch with those of other species, suggesting that they originated from the same ancestor and belong to Attacin_C superfamily. Analysis of quantitative RT-PCR indicated that, after challenged with Escherichia coli, the mRNA level of MdDpt in fly larvae was up-regulated and significantly higher than that of the blank control at 6 h to 12 h post-challenge. These results suggest that MdDpt plays an important role in fly defensive system.

Key words: Musca domestica, antibacterial peptide, diptericin, Md-Diptericin (MdDpt), semi-quantitative RT-PCR