Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456, USA.
Proc Natl Acad Sci U S A. 2011 Aug 23;108(34):14037-42. doi: 10.1073/pnas.1102555108. Epub 2011 Aug 15.
The soil bacterium Bacillus thuringiensis (Bt) is the most successfully used biopesticide in agriculture, and its insecticidal protein genes are the primary transgenes used for insect control in transgenic crops. However, evolution of insect resistance to Bt toxins threatens the long-term future of Bt applications. To date, cases of resistance to Bt toxins have been reported in agricultural situations in six insect species, but the molecular basis for these cases of resistance remains unclear. Here we report that the resistance to the Bt toxin Cry1Ac in the cabbage looper, Trichoplusia ni, evolved in greenhouses, is associated with differential alteration of two midgut aminopeptidases N, APN1 and APN6, conferred by a trans-regulatory mechanism. Biochemical, proteomic, and molecular analyses showed that in the Cry1Ac-resistant T. ni, APN1 was significantly down-regulated, whereas APN6 was significantly up-regulated. The Cry1Ac resistance was correlated with down-regulation of APN1 but not with the up-regulation of APN6. The concurrent up-regulation of APN6 and down-regulation of APN1 might play a role in compensating for the loss of APN1 to minimize the fitness costs of the resistance. Along with identifying reduced expression of APN1 as the molecular basis of Bt resistance selected in an agricultural setting, our findings demonstrate the importance of APN1 to the mode of action of Bt toxin Cry1Ac.
土壤细菌苏云金芽孢杆菌（Bt）是农业中应用最成功的生物农药，其杀虫蛋白基因是转基因作物中用于控制昆虫的主要转基因。然而，昆虫对 Bt 毒素的抗性进化威胁到 Bt 应用的长期未来。迄今为止，在六种农业昆虫物种中已经报道了对 Bt 毒素的抗性案例，但这些抗性案例的分子基础仍不清楚。在这里，我们报告说，在温室中进化出的菜粉蝶（Trichoplusia ni）对 Bt 毒素 Cry1Ac 的抗性与两个中肠氨肽酶 N、APN1 和 APN6 的差异改变有关，这是由一个转录调控机制引起的。生化、蛋白质组学和分子分析表明，在 Cry1Ac 抗性 T. ni 中，APN1 显著下调，而 APN6 显著上调。Cry1Ac 抗性与 APN1 的下调有关，而与 APN6 的上调无关。APN6 的同时上调和 APN1 的下调可能在弥补 APN1 的损失方面发挥作用，以最小化抗性的适应成本。除了确定 APN1 的表达降低是在农业环境中选择 Bt 抗性的分子基础外，我们的研究结果还表明 APN1 对 Bt 毒素 Cry1Ac 的作用模式很重要。
