Gene cloning,expression profiling and anti-microbial assay of Muscin,a new antimicrobial peptide in the housefly(Musca domestica)

【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 c DNA 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 p I 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 broadspectrum 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.