Abstract: As a member of the antimicrobial peptide family, attacin plays a key role in insect innate immune system. In this study, a cDNA of 819 bp encoding attacin-2 was cloned from housefly (Musca domestica) by RACE based on the EST information, and named Mdatta2. The cDNA sequence contains a 726 bp open reading frame (ORF) encoding 241 amino acid residues and is flanked by a 42 bp 5′-UTR and a 51 bp 3′-UTR. The deduced peptide contains a putative signal peptide of 22 amino acids. The amino acid sequence of Mdatta2 showed the highest identity (46%) with that of Drosophila ananassae by Blastp analysis. The phylogenetic tree indicates that the attacin-2 from housefly and those from other dipterans are descended from a single common ancestor and belong to Attain_C superfamily. The expression of Mdatta2 transcript was measured by real-time PCR. The results demonstrated that after housefly larvae were challenged with Escherichia coli and Staphylococcus aureus, respectively, the mRNA level of Mdatta2 at 3 h and 6 h post-challenge was up-regulated and significantly higher than that of the blank control. The expression of Mdatta2 is inducible, and its expression level varies with the induction time, suggesting that Mdatta2 may play an important role in housefly defensive system.

Key words: Musca domestica, antibacterial peptide, attacin, gene cloning, gene expression profiling