Department of Entomology, University of Illinois, Urbana, IL 61801, USA.
Proc Natl Acad Sci U S A. 2011 Aug 2;108(31):12657-62. doi: 10.1073/pnas.1109535108. Epub 2011 Jul 20.
Although Apis mellifera, the western honey bee, has long encountered pesticides when foraging in agricultural fields, for two decades it has encountered pesticides in-hive in the form of acaricides to control Varroa destructor, a devastating parasitic mite. The pyrethroid tau-fluvalinate and the organophosphate coumaphos have been used for Varroa control, with little knowledge of honey bee detoxification mechanisms. Cytochrome P450-mediated detoxification contributes to pyrethroid tolerance in many insects, but specific P450s responsible for pesticide detoxification in honey bees (indeed, in any hymenopteran pollinator) have not been defined. We expressed and assayed CYP3 clan midgut P450s and demonstrated that CYP9Q1, CYP9Q2, and CYP9Q3 metabolize tau-fluvalinate to a form suitable for further cleavage by the carboxylesterases that also contribute to tau-fluvalinate tolerance. These in vitro assays indicated that all of the three CYP9Q enzymes also detoxify coumaphos. Molecular models demonstrate that coumaphos and tau-fluvalinate fit into the same catalytic pocket, providing a possible explanation for the synergism observed between these two compounds. Induction of CYP9Q2 and CYP9Q3 transcripts by honey extracts suggested that diet-derived phytochemicals may be natural substrates and heterologous expression of CYP9Q3 confirmed activity against quercetin, a flavonoid ubiquitous in honey. Up-regulation by honey constituents suggests that diet may influence the ability of honey bees to detoxify pesticides. Quantitative RT-PCR assays demonstrated that tau-fluvalinate enhances CYP9Q3 transcripts, whereas the pyrethroid bifenthrin enhances CYP9Q1 and CYP9Q2 transcripts and represses CYP9Q3 transcripts. The independent regulation of these P450s can be useful for monitoring and differentiating between pesticide exposures in-hive and in agricultural fields.
尽管西方蜜蜂（Apis mellifera）在农业领域觅食时长期接触农药，但在过去二十年中，它在蜂巢内也接触到了以杀螨剂形式存在的农药，以控制毁灭性寄生螨虫瓦螨（Varroa destructor）。拟除虫菊酯tau-氟戊菊酯和有机磷敌敌畏曾用于控制瓦螨，但对蜜蜂解毒机制的了解甚少。细胞色素 P450 介导的解毒作用有助于许多昆虫对拟除虫菊酯的耐受，但负责蜜蜂（甚至任何膜翅目传粉昆虫）中农药解毒的特定 P450 尚未确定。我们表达和测定了 CYP3 族中肠 P450，并证明 CYP9Q1、CYP9Q2 和 CYP9Q3 将 tau-氟戊菊酯代谢为适合进一步被羧酸酯酶切割的形式，而羧酸酯酶也有助于 tau-氟戊菊酯的耐受。这些体外测定表明，所有三种 CYP9Q 酶也能使敌敌畏解毒。分子模型表明，敌敌畏和 tau-氟戊菊酯适合进入同一个催化口袋，这为这两种化合物观察到的协同作用提供了一个可能的解释。蜂蜜提取物诱导 CYP9Q2 和 CYP9Q3 转录本表明，饮食中衍生的植物化学物质可能是天然底物，并且 CYP9Q3 的异源表达证实了其对广泛存在于蜂蜜中的类黄酮槲皮素的活性。蜂蜜成分的上调表明，饮食可能会影响蜜蜂解毒农药的能力。定量 RT-PCR 测定表明，tau-氟戊菊酯增强 CYP9Q3 转录本，而拟除虫菊酯联苯菊酯增强 CYP9Q1 和 CYP9Q2 转录本并抑制 CYP9Q3 转录本。这些 P450 的独立调控可用于监测和区分蜂巢内和农业领域的农药暴露。
