Effects Of BmOXR1 Gene On Immunity Of The Silkworm, Bombyx Mori

Insect is the most abundant species in the natural world with huge quantity and extensive distribution. Under all environment and invasion of pathogens, insects formed the unique innate immune system during the long-term evolution process. Insects’ innate immune system contains humoral immunity and cellular immunity. Reactive oxygen species(ROS) has beneficial effects on the defense mechanisms of immune system. However ROS also causes oxidative stress to the hosts. To avoid it,insects have evolved enzymatic and antioxidant detoxification systems that efficiently scavenge ROS. OXR1(Oxidation Resistance 1)gene is present in all eukaryotes examined so far and protects from oxidative stress.1. We found four BmOXR1 gene transcripts by PCR amplification. Sequence ananlysis showed the differeces of the four transcrips are at the uptream and the most highly conserved region of the gene is the carboxl-terminal TLDc domain.2. BmOXR1 gene was up-regulated in the fat body after injection of Pseudomonas aeruginosa or Staphylococcus aureus at different time points revealed by semi-quantitative RT-PCR. It suggests that BmOXR1 may be involved in Bombyx mori immune response.3. BmOXR1 gene was up-regulated in the fat body after injection of H2O2 at different time points, with the mainly expressed transcripts AK387280 and AK383272_n. It suggests that AK387280 and AK383272_n might be the major forms in the silkworm antioxidation system.4. We found that BmOXR1 gene expression was inhibited by JNK inhibitor treatment after injection of bacteria or H2O2, and larvae mortality was reduced and the concentration of H2O2 increased in haemolymph. Colony unit forming(CFU) assay indicated that both P. aeruginosa and S. aureus were inhibited. we consider that the rise of H2O2 in haemolymph affected the growth of P. aeruginosa and S. aureus. We found that P. aeruginosa is sensitive to H2O2, while S. aureus tolerate to it.In conclusion, BmOXR1 gene is induced by bacterial infection and oxidative stress, indicating that BmOXR1 is involved in silkworm immune response. We further showed BmOXR1 is regulated by JNK pathway.