Study Of Function Mechanism Of Bt Cry1Ac Toxin To Helicoverpa Armigera And Mythimna Separata

Bacillus thuringiensis (Bt) is the most important insecticide in the field of biological control. The Bt transgenic cotton is high-effective for keeping Helicoverpa armigera, an important worldwide agricultural insect pest. As the growing area of Bt cotton has been increasing rapidly, the development of resistance to Bt in H. armigera becomes obvious. Mythimna separata is also an important agricultural insect pest. With the growing rate of resistance to Bt, function mechanism of Bt to insect and resistance mechanism of insect to Bt are studied widely. Function mechanism of Bt to Helicoverpa armigera and Mythimna separata is studied in this thesis. The results are as follows:1 Bt CrylAc toxin has high toxicity to H. armigera, but has low toxicity to M. separata. And these two insects are sensitive to pro-toxin than toxin.2 Bt Cry1AcE toxins are composed of many peptides which have 60 kD weight, and all parts have biological activity to insect, not single part has activity.3 The mid-gut juice enzyme activity of M. separata is higher than H. armigera. 130kD Bt pro-toxin is decomposed by mid-gut juice in 37℃ and 30min and 60 min , 60kD toxin can be got by H. armigera and M. separata mid-gut juice, but, other less than 60kD proteins also can be got by M. separata mid-gut juice .4 Many Bt Cry1AcE toxins can be got by the method of precipitate and resolve, which have high purity. The antibody of toxin can be got by immunizing rabbit, which has high activity and been used to Western blotting successfully.5 APN activity of gut is higher than other tissues in H. armigera and Mythimna separata, and only the sample of gut can hybridize with Bt Cry1AcE toxin.6 Many membrane proteins can be got by dissoluted in H. armigera BBMV, on the contrary few membrane proteins can be got by dissoluted in M. separata BBMV, and the concentration of membrane protein in M. separata BBMV is lower than in H. armigera BBMV.7 The 120kD Bt CrylAcE toxin receptor is tested by Western blotting, which is one of H.armigera BBMV membrane proteins.