Lin George Guan-Hua, Scott Jeffrey G
Department of Entomology, Comstock Hall, Cornell University, Ithaca, NY 14853, USA.
Pestic Biochem Physiol. 2011 Jun;100(2):130-134. doi: 10.1016/j.pestbp.2011.02.012.
House fly (Musca domestica) CYP6D1 is a cytochrome P450 involved in metabolism of xenobiotics. CYP6D1 is located on chromosome 1 and its expression is inducible in response to the prototypical P450 inducer phenobarbital (PB) in insecticide susceptible strains. Increased transcription of CYP6D1 confers resistance to permethrin in the LPR strain, and this trait maps to chromosomes 1 and 2. However, the constitutive overexpression of CYP6D1 in LPR is not further increased by PB and the non-responsiveness to PB maps to chromosome 2. It has been suggested that a single factor on chromosome 2 could be responsible for both the constitutive overexpression and lack of PB induction of CYP6D1 in LPR. We examined the PB inducibility of CYP6D1v1 promoter from LPR using dual luciferase reporter assays in Drosophila S2 cells and found the CYP6D1v1 promoter was able to mediate PB induction, similar to the CYP6D1v2 promoter from the insecticide susceptible CS strain. Therefore, variation in promoter sequences of CYP6D1v1 and v2 does not appear responsible for the lack of PB induction of CYP6D1v1 in LPR; this suggests an unidentified trans acting factor is responsible. HR96 has been implicated in having a role in PB induction in Drosophila melanogaster and M. domestica. Therefore, house fly HR96 cDNA was cloned and sequenced to examine if this trans acting factor is responsible for constitutive overexpression of CYP6D1v1 in LPR. Multiple HR96 alleles (v1-v10) were identified, but none were associated with resistance. Expression levels of HR96 were not different between LPR and CS. Thus, HR96 is not the trans acting factor responsible for the constitutive overexpression of CYP6D1 in LPR. The identity of this trans acting factor remains elusive.
家蝇（Musca domestica）的CYP6D1是一种参与异源物质代谢的细胞色素P450。CYP6D1位于1号染色体上，在杀虫剂敏感品系中，其表达可被典型的P450诱导剂苯巴比妥（PB）诱导。CYP6D1转录增加使LPR品系对氯菊酯产生抗性，且该性状定位于1号和2号染色体。然而，LPR中CYP6D1的组成型过表达不会因PB而进一步增加，对PB的无反应性定位于2号染色体。有人提出，2号染色体上的单一因子可能是LPR中CYP6D1组成型过表达和缺乏PB诱导的原因。我们在果蝇S2细胞中使用双荧光素酶报告基因检测法检测了LPR中CYP6D1v1启动子的PB诱导性，发现CYP6D1v1启动子能够介导PB诱导，类似于杀虫剂敏感CS品系的CYP6D1v2启动子。因此，CYP6D1v1和v2启动子序列的差异似乎不是LPR中CYP6D1v1缺乏PB诱导的原因；这表明存在一个未知的反式作用因子。HR96被认为在黑腹果蝇和家蝇的PB诱导中起作用。因此，克隆并测序了家蝇HR96 cDNA，以检查这个反式作用因子是否是LPR中CYP6D1v1组成型过表达的原因。鉴定出了多个HR96等位基因（v1-v10），但没有一个与抗性相关。LPR和CS之间HR96的表达水平没有差异。因此，HR96不是负责LPR中CYP6D1组成型过表达的反式作用因子。这个反式作用因子的身份仍然难以捉摸。
