Identification and characterization of the cysteine protease inhibitor gene MdCPI from Musca domestica

Involvement of trehalose-6-phosphate synthase in innate immunity of Musca domestica

Trehalose-6-phosphate synthase (TPS) is responsible for synthesizing trehalose, which is prevalent in crustaceans and insects as blood-sugar. In this paper, a TPS gene from Musca domestica(MdTPS)has been cloned and characterized. MdTPS promoter was analyzed, and its transcriptional activity was verified in vitro by Sf9 cell. Quantitative RT-PCR analysis revealed that the MdTPS transcription was up-regulated following bacterial challenge by Escherichia coli or Staphylococcus aureus. Meanwhile, trehalose is accumulated in larvae upon bacterial challenge. Significantly increased mortality can be observed in MdTPS depleted (RNA interference, RNAi) larvae under bacterial infection. Interestingly, feeding trehalose led to increasing trehalose content in larvae, and the effects of RNAi targeting MdTPS on host survival against bacterial challenge was partly counteracted. Taken together, these results suggest that MdTPS acts as an inducible anti-stress gene that takes part in immune defense in M. domestica via synthesizing its product trehalose.

Stress-induced HSP70 from Musca domestica plays a functionally significant role in the immune system

As important molecular chaperones, members of the 70kDa heat shock protein (HSP70) family play essential roles in stress tolerance and innate immunity in organisms. The full-length complementary DNA (cDNA) of a novel inducible HSP70, named as MdHSP70, was isolated from Musca domestica. The cDNA clone consisted of 2411 bp with a 1956 bp open reading frame which encodes 651 amino acids. Using real-time quantitative polymerase chain reaction (qPCR), we investigated the transcriptional profile of the gene under heat shock, cadmium stress and in response to bacteria. Increased expression of MdHSP70 was observed in response to both heat shock and Cd stress. The expression of MdHSP70 was significantly induced by Escherichia coli or Staphylococcus aureus stimulation. Larvae were fed bacteria expressing dsRNA targeting the MdHSP70 gene. Our results showed high mortality in larvae treated with dsRNA of MdHSP70 at heat shock, Cd stress and bacterial invasion, suggesting that MdHSP70 is potentially involved in the stress and immune responses of the house fly and perhaps contributes to protection against cellular injury.