关键词: 家蝇, Sirtuins蛋白, 免疫, 热激, 重金属胁迫

Abstract: 【Aim】 This study aims to explore the expression pattern of Musca domestica sirt1 gene (Mdsirt1) under various stress conditions. 【Methods】 The sequence of Mdsirt1 gene was cloned by PCR from the 2nd instar larvae of Musca domestica and subjected to bioinformatics analysis. The expression profiles of Mdsirt1 in different developmental stages (egg, 1st instar larva, 2nd instar larva, 3rd instar larva, pupa and adult), various tissues of the 2nd instar larvae (cuticle, gut, fat body and hemocyte), and the 2nd instar larvae under stresses (challenged by bacteria, heat shock and CdCl₂ stimulation) were investigated via quantitative real-time PCR (qRT-PCR). RNAi was employed to knock down the expression of Mdsirt1 in M. domestica larvae by microinjection with dsRNA, and then the resistance of larvae to bacteria and oxidative stress was detected. 【Results】 The deduced protein encoded by Mdsirt1 contains a predicted SIR2 domain, and shows 66% sequence identity with SIR2 from Stomoxys calcitrans. qRT-PCR results showed that Mdsirt1 was mainly transcribed in the pupal stage and fat body of the 2nd instar larvae of M. domestica. Enhanced expression of Mdsirt1 was observed in response to Escherichia coli and Staphylococcus aureus challenge for 3 and 6 h, respectively. The expression of Mdsirt1 was significantly induced by heat shock of 42℃ for 30 min, and cadmium stimulation (exposure to 30 mmol/L CdCl₂) for 48 h. The survival rate observed in larvae treated with dsRNA of Mdsirt1 under bacterial challenge (E. coli∶S. aureus=1∶1) was 1.47-fold lower than that treated with dsRNA of GFP. RNAi-mediated knockdown of Mdsirt1 led to oxidative stress, and caused rapid increase of 1.58- and 1.59-fold in the reactive oxygen species (ROS) level and malondialdehyde (MDA) content, respectively. 【Conclusion】 Mdsirt1 is involved in immunity and stress resistance in M. domestica larvae.

Key words: Musca domestica, sirtuins, immunity, heat shock, heavy metal stress