亚致死剂量氟啶虫胺腈对灰飞虱细胞色素P450的影响

为明确氟啶虫胺腈对灰飞虱Laodelphax striatellus细胞色素P450的影响,评估其抗药性风险,采用点滴法、酶活力分析法和实时荧光定量PCR法分别测定了氟啶虫胺腈对灰飞虱的毒性及对其细胞色素P450酶活力和P450基因表达量的影响。结果表明,氟啶虫胺腈对灰飞虱的致死中量LD_(50)随着虫龄的增加而升高,1~5龄若虫的LD_(50)为0.10~0.94 ng/头,雌、雄成虫的LD_(50)分别为1.09 ng/头和1.07 ng/头。氟啶虫胺腈对4龄若虫的亚致死剂量LD_(10)、LD_(30)和LD_(50)分别为0.17、0.41、0.76 ng/头,处理灰飞虱4龄若虫后可将其体内P450酶活力分别显著提高1.60、1.97和1.22倍;而各处理响应的P450基因的种类和数量不同,但相对表达量均受到诱导;CYP4DE1、CYP426A1、CYP303A1、CYP4C、CYP6FK1和CYP4C71v2的相对表达量表现出时间效应,表达量高峰在处理后24 h或48 h。表明不同亚致死剂量的氟啶虫胺腈在特定时间点可提高相应的细胞色素P450基因表达量,从而使酶蛋白量增加,可能导致灰飞虱体内细胞色素P450酶活力上升。

Effects of sublethal sulfoxaflor on cytochrome P450 of the small brown planthopper, Laodelphax striatellus

To determine the sublethal effects of sulfoxaflor on cytochrome P450 in small brown planthopper, Laodelphax striatellus, and assess its resistance risk, the topical bioassay was performed to test the acute toxicity of sulfoxaflor on L. striatellus, and enzyme activity assay and real-time PCR assay were adopted to study cytochrome P450 enzyme activity and gene expression changes. Lethal medial dose(LD₅₀)of sulfoxaflor on L. striatellus increased with growth, which was 0.10-0.94 ng per pest on first to fifth instar nymphs, and 1.09 ng per pest and 1.07 ng per pest on female and male adults. Cytochrome P450 enzyme activities of fourth instar nymphs were significantly enhanced by 1.60, 1.97 and 1.22 folds under LD₁₀ (0.17 ng per pest), LD₃₀ (0.41 ng per pest) and LD₅₀ (0.76 ng per pest), respectively. The relative expression levels of different types and numbers of cytochrome P450 genes were increased in response to sublethal sulfoxaflor. The relative expression levels of CYP4DE1, CYP426A1, CYP303A1, CYP4C, CYP6FK1 and CYP6FK171v2 exhibited inducement effects which showed peak at 24 h or 48 h. Sulfoxaflor could significantly increase cytochrome P450 enzyme activity by enhancing multiple cytochrome P450 gene expressions at a particular time point.