吡虫啉对褐飞虱DNA甲基化多态性的影响

为了探知基因组甲基化是否参与了昆虫抗药性， 本研究在室内对褐飞虱 Nilaparvata lugens连续9个世代的3龄若虫施用吡虫啉， 用AFLP检测褐飞虱抗性产生过程中DNA甲基化多态性的变化。利用25对AFLP引物共获得120个位点， 其中15个位点呈现甲基化多态性， 共获得78条多态性条带。根据多态性条带在不同世代样本中出现的多少计算多态性条带比例， 其中最高比例出现在G5代（10.26%）， 最低比例出现在G6代（1.28%）。多态性条带在不同世代间比例的变化趋势表明， 褐飞虱对吡虫啉的筛选产生快速应答。在筛选早期（G1， G2和G3）世代间DNA甲基化多态性比例差异相对较小， 变化范围在3.85%～6.41%之间； 在筛选中期（G4， G5和G6）世代间比例差异较大， 变化范围在1.28%～10.26%之间； 在筛选后期（G7， G8和G9）世代间比例差异相对较小， 变化范围在5.13%～7.69%之间。结果说明， 吡虫啉的连续施用能够诱导褐飞虱基因组产生甲基化变异， 初步揭示甲基化在褐飞虱抗药性产生过程中参与了基因组的表达调控。

Effects of imidacloprid on DNA methylation polymorphism in the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae)

In order to clarify whether DNA methylation takes part in insecticide resistance, the 3rd instar nymphs of the brown planthopper, Nilaparvata lugens, in 9 generations were sprayed by imidacloprid continuously in the laboratory, and AFLP technique was used to test the variation in DNA methylation polymorphism of the brown planthopper during the continuous application of imidacloprid. Using 25 pairs of AFLP primers, we obtained 120 loci, of which 15 loci displayed polymorphism within samples and a total of 78 polymorphic bands were obtained for these loci. The highest and lowest rates of polymorphic bands, 10.26% and 1.28%, occurred at the 5th and 6th generation, respectively. The change trend of polymorphism indicated that in the early screening stage (the earliest three generations), the brown planthopper had quick responses to imidacloprid with the rates of polymorphic bands of 3.85%-6.41%; in the middle screening stage (from the 4th to 6th generation), its responses fluctuated substantially with the rates of polymorphic bands of 1.28%-10.26%; and in the late screening stage (from the 7th to 9th generation), its responses varied very little with the rates of polymorphic bands of 5.13%-7.69%. These results suggest that imidacloprid can induce DNA methylation in the brown planthopper, therefore onset of resistance to insecticides, and DNA methylation may take part in the genome defense of planthoppers to imidacloprid selection.