Abstract: As a member of the antioxidant enzymes, superoxide dismutase (SOD) plays a key role in insect antioxidant protection system. In this study, the full-length cDNA of a SOD gene MdSOD3 (GenBank accession no. JQ408979) from the housefly, Musca domestica, was cloned and characterized by RT-PCR, which is 817 bp in length, the open reading frame is 534 bp encoding 177 amino acid residues. The homologous alignment and phylogenetic tree indicate that the MdSOD3 from housefly belongs to Cu/ZnSOD family. The temporal expression profiling revealed that MdSOD3 was present in the fat body, gut, hemocytes and cuticle. The expression of MdSOD3 was enhanced by Cd stress. The highest expression level was found in treatment at 5 mmol/L Cd²⁺ within a 24 h period. Quantitative PCR (qPCR) showed that mRNA level of MdSOD3 gene was reduced compared to the control by RNAi. High mortality was observed in the larvae treated with dsRNA of MdSOD3 for 60 h at 5 mmol/L Cd stress for 24 h. The RNAi of MdSOD3 gene resulted in the larval abdominal apex to become black. The results suggest that MdSOD3 may play an important role in adapting to heavy metal stress in housefly.

Key words: Musca domestica, superoxide dismutase (SOD), quantitative PCR, RNAi, heavy metal stress