| Resistance to insecticides is an important factor affecting the effects of chemical prevention, understanding the mechanism is an important part of integrated pest management. The rising of insect detoxification metabolism enzyme activity is the important mechanism of the pests resistant to many insecticides, the most studied by people is Mixed function oxidase, Esterase and Glutathlone S-transferase, etc. Many researches have reported that these enzymes contribute to resistance, butthese metabolic enzymes or target sites cannot explain some cases of resistancein the actual production, may be there are other metabolic resistance mechanisms. Studies have reported the insect glucosyltransferase participates in the metabolism of exogenous compounds, so speculating that the enzyme has relation with detoxification metabolism of insecticides in insects.This paper establishes a method for the measurementof UGT enzymes, finds out the best condition for enzyme activity, analysis and comparison of UGT activity in Spodoptera litura two strains, the different state, the different organization and the changes of UGT activity after exposed to insecticides.1. A method for the measurementof UGT enzymesIn order to measure the size of the UGT enzymes accurately, we must establish the best condition for the measurementof UGT enzymes. This paper find out the optimum conditions for measurement of UGT enzymes by repeated experiments, such as some variables:temperature, pH, buffer, substrate concentration and the concentration of enzymes. The results show that, adopting the dynamics methods, T=37℃, pH=8.5, Mg2+ =10mM,PBS buffer, a-naphthol as substrate, UDP-glucose providing glycosyl, glycosylation reactions, generating 1-naphthylglucoside, the glycoside formation is continuously monitored use the excitation wavelength 287 nm and the emission wavelength 335 nm, with 5 nm slit width. It reflects the size of enzyme activity by detecting the changes of fluorescence intensity value.2. The distribution ofUGT activity in Spodoptera lituraBecause this study put the agricultural important pests-Spodoptera litura-as a selected insects, as the same time, preparing for the following experiment, so must know the distribution of UGT enzymesin Spodoptera litura. This experiment compare the two strains UGT enzymes of Spodoptera lituraand find the UGT enzyme activity of the resistance populationhigher than the susceptibility population; By means of the comparison of UGT enzymes in thedifferent insect state and different organizations of Spodoptera litura, the results showed, theUGT enzymes activities of Spodoptera litura larvaes higher than the adults、the pupas、the eggs, and the larvae UGT enzymes were not significantly different between different age; the UGT enzymes activities in the midgut organization of Spodoptera litura is the highest, the fat body is second, the head is the lowest.3. The change of UGT activity in Spodoptera litura after exposed to insecticidesThis paper detects the changes of UGT activity after exposed to some insecticides, so as to estimate the contribution in detoxification of UGT enzymes to insecticides metabolic, which to further understand the mechanism of insect resistance. In comprehensive governance guidance, the resistance of pest control and management has a positive meaning. The Spodoptera litura has the diffierent resistance revels for the followingpesticides, which are indoxacarb、chlorantraniliprole、metaflumizone、endosulfan、deltamethrin、tebufenozide and emamectin-benzoate. In this paper UGT enzymes induced experiments, the mainly treatment methods of pesticide are the insect immersion method and leaf immersion method. The results showed,after exposed to pesticides which are indoxacar、chlorantraniliprole、 endosulfan、deltamethrin、tebufenozide and emamectin-benzoate insect UGT activity risesto a certain extent, but after exposed to metaflumizone, the UGT activity almost don’t change; different pesticide processing, the response time of UGT enzymes are not identical. |
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