Cytochrome P450 Monooxygenases In Strain Of Tribolium Castaneum (herbst) Resistance To Phosphine

In order to explore the role of cytochrome P450 on the resistance of strain of Tribolium castaneum against phosphine in this paper, researches were carried out on selecting resistant strains, determining the level of resistance, the role of the inhibitors, the level of cytochrome P450 and activity of cytochrome P450 monooxygenase. Finally, the different expression of three P450 genes in sensitive and resistant strains was primary studied in Tribolium castaneum.The main results are as following:(1)The resistance of AK, SQ(F₀), SQ(F₁), SQ(F₂), SQ(F₃), SQ(F₄), SQ(F₅), SQ(F₆), SQ(F₇) to phosphine were measured by quick knockdown method and FAO recommended method.The regressive relationship of knockdown time (KT50) and the result of FAO recommended method is Log(LC₅₀)=1.24 log(KT₅₀)-3.36, the R² is 0.997.(2) After 6 generations selection with high concentration phosphine, the LC₅₀ value of the resistant strain SQ(F₁) increased to 5.21mg/L, it is 854.10 times as that of sensitive strain.The results showed that the resistance developed faster under the high concentration, while for high level resistance the growth is rather slowly.(3)The results showed that resistant strains of SQ(F₀), SQ(F₁), SQ(F₄)dealed with cytochrome P450 inhibitors PBO (piperonly butoxide) were synergistic in multiples of 1.03, 1.07 and 1.12 times respectively, and it was positively correlated with the multiple resistance,the synergistic effect of PBO on resistance increasing were not obvious;(4)The amounts of cytochrome P450 enzymeand b₅ enzyme of resistant strains were higher than those in susceptible strains, and those in was in the adult maximum resistant strain more than 2.13 and 2.96 times respectively as those in the susceptible strains.There was a good correlation between increased contents of b₅ and P450. Those results indicated that some type of coordinated control of the levels of these two components in the development of resistance;(5)The enzyme activities of p-nitroanisoleO-demethylation(PNOD),methoxyresorufin O-demethylation(MROD) and ethoxycoumarin O-deethylation(ECOD) were compared between the SS and the RS. In comparison to susceptible strains, RS had higher activity, using different substrates, MROD, EROD, ECOD and PNOD were significantly elevated by 1.38, 1.65 and1.36-times, respectively. The activities of P450 reductase has no change in different resietant strains.(6)The expression of three cytochrome P450 genes in different strains of larvae were difference in different tissues.The expression of resistant strains SQ (F₀) in the intestinal tissue CYP4Q7,CYP4Q4, CYP genes were similar to the genes is sensitive to strain 2.00,3.74,1.74 times.