Li X, Berenbaum M R, Schuler M A
Department of Plant Protection, Nanjing Agricultural University, PR China.
Insect Biochem Mol Biol. 2000 Jan;30(1):75-84. doi: 10.1016/s0965-1748(99)00102-2.
Xanthotoxin, a plant allelochemical, induces alpha-cypermethrin insecticide tolerance in Helicoverpa zea (corn earworm); inhibition of tolerance by piperonyl butoxide implicates cytochrome P450 monooxygenases (P450s) in the detoxification of this insecticide. To characterize the xanthotoxin-inducible P450 that might mediate alpha-cypermethrin tolerance in this species, a cDNA library prepared from xanthotoxin-induced H. zea fifth instar larvae was screened with cDNAs encoding furanocoumarin-metabolizing P450s from Papilio polyxenes (CYP6B1v2) and P. glaucus (CYP6B4v2) as well as a sequence-related P450 from Helicoverpa armigera (CYP6B2). One full-length cDNA isolated in this screening shares 51-99% amino acid identity with the CYP6B subfamily of P450s isolated from Papilio and Helicoverpa species and, thus, has been designated CYP6B8. All of these CYP6B subfamily members share a number of highly conserved domains, including substrate recognition site 1 (SRS 1) that is critical for xanthotoxin metabolism by CYP6B1v2 from Papilio polyxenes and coumarin metabolism by CYP2a5 from Mus musculus. Northern and RT-PCR analyses indicate that CYP6B8 expression is strongly induced by xanthotoxin and phenobarbital and negligibly induced by alpha-cypermethrin.
黄曲霉毒素是一种植物化感物质，可诱导玉米螟对高效氯氰菊酯产生耐受性；胡椒基丁醚对耐受性的抑制表明细胞色素P450单加氧酶（P450s）参与了这种杀虫剂的解毒过程。为了鉴定可能介导该物种对高效氯氰菊酯耐受性的黄曲霉毒素诱导型P450，用编码来自金凤蝶（CYP6B1v2）和北美蓝凤蝶（CYP6B4v2）的呋喃香豆素代谢P450以及来自棉铃虫的序列相关P450（CYP6B2）的cDNA筛选了从黄曲霉毒素诱导的玉米螟五龄幼虫制备的cDNA文库。在该筛选中分离出的一个全长cDNA与从凤蝶属和棉铃虫属物种中分离出的P450的CYP6B亚家族具有51-99%的氨基酸同一性，因此被命名为CYP6B8。所有这些CYP6B亚家族成员都共享一些高度保守的结构域，包括底物识别位点1（SRS 1），该位点对于金凤蝶的CYP6B1v2代谢黄曲霉毒素和小家鼠的CYP2a5代谢香豆素至关重要。Northern和RT-PCR分析表明，CYP6B8的表达受到黄曲霉毒素和苯巴比妥的强烈诱导，而受到高效氯氰菊酯的诱导作用可忽略不计。
