The Study On Immunological And Stress Response Of Exogenous Material In Ostrinia Furnacalis Guenée (Lepidoptera: Pyralidae) Larvae

The invasion of exogenous material may cause immunological and stress response in Ostrinial furnacalis Guenée larvae. In this study, the pathogen of Escherichia coli and Sephadex G50 beads were injected into O. furnacalis larvae, and the mechanism of cellular and humoral immunity and stress response were studied. The main results are as follows:1,A kind of antibacterial peptide was induced in O. furnacal larvae when injected with E. coli cell at the concentration of 3.0×106 cell/mL. The relative molecular weight of this antibacterical peptide was 7.2 kDa analyzed with SDS-PAGE. The expression of antibacterical peptide increased with the prolong of inducing time in some peroid. Both gram positive (G+) and gram negative (G-) bacterial could be inhibited by this antibacterial peptide. There was significant antibacterial activity when the antibacterial peptide was treated at 100℃for 5 min. The activity of the antibacterial peptide was the highest at the pH value of 8.0, and the diameter of inhibition zones was 7.6±0.8 mm.2,The number of granular cells and plasmatocytes and the total hemocytes count (THC) in the hemolymph of O. furnacalis increased significantly after injection with E. coli cells at different concentrations (p<0.01), and the content of reactive oxygen species (ROS) and the PO activity also increased in the larvae. The activity of GSH-pX and GST in all tissue and the GR in serum inceased markedly (p<0.01). However, the THC and the number of granular cells and plasmatocytes and the activity of GSH-pX, GR, GST and the content of ROS in the larvae decreased significantly when injected with 3×105 cells and 3×106 cells after 12 h. The distribution of GSH-pX, GST and GR were different in various tissue, and the GSH activity was the highest in the fatbody and the lowest in the integument, the GR activity was the highest in the integument and the lowest in the serum, GST activity was the highest in the serum and the lowest in the integument. But the PO activity was the highest in the serum, then integument, and the lowest in the hemocytes lysate of the larvae.3,The shape of all kinds of hemocytes in the O. furnacalis larvae was not changed significantly when injected with Sephadex G50, however the THC and the number of granular cells and plasmatocytes increased significantly (p<0.05). In the process of encapsulation of hemocytes on the sephadex G50, the rate of beads encapsulated>the rate of beads adhered with cells>the rate of beads without adhered cells. The PO activity was also induced markedly by the injection with Sephadex G50 (p<0.01).