Abstract: 【Aim】 The objective of this research is to investigate the immunological functions of peptidoglycan recognition protein SC in the housefly, Musca domestica, in response to invading bacteria. 【Methods】 We knocked down the expression level of MdPGRP-SC  by feeding the newly-hatched larvae of M. domestica with Escherichia coli expressing double-strand RNA and then measured the interference effect with quantitative real-time PCR (qPCR). The treated larvae were fed with GFP-expressing E. coli, and then the tempo-spatial dynamics of these ingested bacteria was observed under fluorescent microscope. The hydrogen peroxide content and the expression profiles of antimicrobial peptide genes in the intestine of the larvae fed with dsRNA were tested by colorimetry and qPCR methods, respectively. 【Results】The qPCR results showed a significant decrease in the relative expression level of PGRP-SC in the interference group. After M. domestica  larvae fed with E. coli expressing GFP, a rapid fadeout of fluorescence in the MdPGRP-SC interference group was observed compared with the GFP control group. The hydrogen peroxide content in each group had no significant change, while the expression levels of all the four AMP genes were up-regulated dramatically in the gut of MdPGRP-SC depleted larvae. 【Conclusion】 MdPGRP-SC plays a role in regulating the sensitivity of intestinal immune reaction in housefly larvae.

Key words: Musca domestica, intestinal immune, peptidoglycan recognition protein, reactive oxygen species, antimicrobial peptide