关键词: 家蝇, C-型凝集素, RNAi, 细菌刺激, 先天免疫, 模式识别受体

Abstract: 【Aim】 This study aims to identify and characterize a new C-type lectin gene from the housefly Musca domestica, and to analyze its immune function. 【Methods】 Based on the transcriptome database, a new lectin gene, designated as  Mdlectin-C1, was cloned from M. domestica. Recombinant Mdlectin-C1 was expressed in Escherichia coli,and purified rMdlectin-C1 was used to prepare polyclonal antibody. Quantitative real-time PCR (qRT-PCR) and Western blot techniques were employed to investigate the gene expression profiles in different developmental stages and larvae post bacterial infection. The survival rate of the 1st instar larvae subjected to Mdlectin-C1 RNAi was detected after bacterial challenge. 【Results】 The cDNA sequence of Mdlectin-C1 contains a 546 bp open reading frame encoding 181-amino-acid residues. A putative signal peptide of 21-amino-acid residues is present at the N-terminus. A conservative carbohydrate recognition domain (CRD) is observed in the mature peptide. The results of qRT-PCR and Western blot revealed that the expression level of Mdlectin-C1 was gradually enhanced fromthe 2nd instar larval stage to the pupal stage and reached the maximum value at the pupal stage. The expression level of Mdlectin-C1 was up-regulated significantly in larvae at 36 and 3 h after challenge with Gram-negative bacterium E. coli and Gram-positive bacterium Staphylococcus aureus, respectively. qRT-PCR analysis showed that the expression level of Mdlectin-C1 was knocked down successfully by RNAi. The survival rate of the 1st instar larvae subjected to Mdlectin-C1 RNAi was significantly lower than the normal control post bacterial challenge. 【Conclusion】 Mdlectin-C1 is involved in antimicrobial immune response in the housefly and may play important roles in this process.

Key words: Musca domestica, C-type lectin, RNAi, bacterial challenge, innate immune, pattern recognition receptor