Transgenic crops producing crystalline (Cry) proteins from the bacterium Bacillus thuringiensis (Bt) have been used extensively to control some major crop pests. However, many populations of the noctuid moth Helicoverpa zea , one of the most important crop pests in the United States, have evolved practical resistance to several Cry proteins including Cry1Ac. Although mutations in single genes that confer resistance to Cry proteins have been identified in lab-selected and gene-edited strains of H. zea and other lepidopteran pests, the genetic basis of field-evolved resistance to Cry proteins in H. zea has remained elusive. We used a genomic approach to analyze the genetic basis of field-evolved resistance to Cry1Ac in 937 H. zea derived from 17 sites in seven states of the southern United States. We found evidence for extensive gene flow among all populations studied. Field-evolved resistance was not associated with mutations in 20 single candidate genes previously implicated in resistance or susceptibility to Cry proteins in H. zea or other lepidopterans. Instead, resistance in field samples was associated with increased copy number of a cluster of nine trypsin genes. However, trypsin gene amplification occurred in a susceptible sample and not in all resistant samples, implying that this amplification does not always confer resistance and mutations in other genes also contribute to field-evolved resistance to Cry1Ac in H. zea . The mismatch between lab-generated and field-evolved resistance in H. zea is unlike other cases of Bt resistance and reflects challenges for managing this pest.

中文翻译：

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玉米 Helicoverpa 玉米中实验室生成和田间进化对转基因 Bt 作物的抗性不匹配


从苏云金芽孢杆菌 （Bt） 中产生结晶 （Cry） 蛋白的转基因作物已被广泛用于控制一些主要作物害虫。然而，夜蛾 Helicoverpa zea 的许多种群是美国最重要的农作物害虫之一，已经进化出对包括 Cry1Ac在内的几种 Cry 蛋白的实际抗性。尽管在实验室选择和基因编辑的玉米猿和其他鳞翅目害虫菌株中已经确定了赋予 Cry 蛋白抗性的单个基因突变，但玉米猿中对 Cry 蛋白的田间进化抗性的遗传基础仍然难以捉摸。我们使用基因组方法分析了来自美国南部 7 个州的 17 个地点的 937 个 H. zea 对 Cry1Ac 的田间进化抗性的遗传基础。我们发现了所有研究人群中广泛基因流动的证据。场进化的抗性与 20 个单个候选基因的突变无关，这些基因以前与 H. zea 或其他鳞翅目动物对 Cry 蛋白的抗性或易感性有关。相反，田间样品中的抗性与 9 个胰蛋白酶基因簇的拷贝数增加有关。然而，胰蛋白酶基因扩增发生在易感样本中，而不是所有耐药样本中，这意味着这种扩增并不总是赋予耐药性，其他基因的突变也有助于玉米嗜血杆菌对 Cry1Ac 的场进化耐药性。玉米嗜血杆菌的实验室产生和田间进化的抗性之间的不匹配与其他 Bt 抗性情况不同，反映了管理这种害虫的挑战。