Abstract: 【Aim】 The objective of this research is to identify and characterize a new antimicrobial peptide (Muscin) gene from the housefly, Musca domestica (Linnaeus). 【Methods】 Based on the digital gene expression profiling (DGE) and bioinformatics analysis, a potential antimicrobial peptide gene, muscin, was identified from the housefly transcriptome database. Quantitative real-time PCR (qRT-PCR) was employed to investigate the tissue distribution of muscin mRNA and its temporal expression in housefly larvae challenged with the mixture of bacteria Escherichia coli and Staphylococcus aureus. The anti-microbial and hemolytic activities of the synthetic peptide were also tested. 【Results】 The full-length cDNA of muscin is 379 bp, with an open reading frame of 153 bp encoding a peptide of 50 amino acid residues. The deduced peptide contains a putative signal peptide of 25 amino acids. The deduced mature peptide is rich in hydrophobic and positively charged amino acid residues with a theoretical pI of 9.39. The qRT-PCR results showed that muscin was mainly transcribed in the hemocytes and fat body. Post immunity induction with the mixture of bacteria, the expression of muscin was up-regulated and reached the maximal level at 6 h. Anti-microbial assays and hemolytic test displayed that c-Muscin had broad-spectrum antibacterial activity against Gram positive and Gram negative bacteria, and a low hemolytic activity. 【Conclusion】 Muscin is a novel broad-spectrum antimicrobial peptide with potential medicinal value and may take part in immune defense against bacterial pathogens in the housefly.

Key words: Musca domestica, antimicrobial peptide, gene cloning, bioinformatical analysis, expression level, antibacterial activity, hemolytic test