Since 1996, transgenic Bacillus thuringiensis (Bt) cotton has been commercially grown in numerous countries in an effort to stem the losses caused by key lepidopteran pests. However, the development of pest resistance to Bt toxins has jeopardized the continued utilization of Bt cotton. As a strategy designed to circumvent the development of resistance, Bt cotton varieties expressing two or more toxins targeting the same pest have been introduced. Nevertheless, from the perspective of long-term planting of Bt cotton, the potential risk of cross-resistance to these Bt toxins is a threat that cannot be ignored. In this paper, we review current research (including that based on the analysis of protein binding sites and resistance genes) on the resistance of cotton bollworm ( Helicoverpa armigerd ) to the Bt toxins Cry1Ac and Cry2Ab and the interrelationship between these toxins. On the basis of existing evidence, we assume that the actions of Cry1Ac and Cry2Ab against cotton bollworm are not completely independent, and then propose the “resistance-associated gene mutation potential hypothesis”. Although the mechanisms underlying the resistance of pests to Bt toxins are yet to be comprehensively elucidated, this hypothesis could undoubtedly have important implications for adopting “pyramid” strategy in the future. Further research is recommended to devise strategies to retard the development of H. armigera resistance to Bt cotton, either using different Bt toxins or their various combinations.

中文翻译：

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棉铃虫对苏云金芽孢杆菌毒素 Cry1Ac 和 Cry2Ab 是否显示交叉抗性？一个小评论

自 1996 年以来，转基因苏云金芽孢杆菌 (Bt) 棉花已在许多国家进行商业种植，以阻止主要鳞翅目害虫造成的损失。然而，害虫对 Bt 毒素抗性的发展已经危及 Bt 棉花的继续利用。作为一种旨在规避抗性发展的策略，已经引入了针对同一害虫表达两种或多种毒素的 Bt 棉花品种。尽管如此，从长期种植Bt棉花的角度来看，对这些Bt毒素的交叉抗性的潜在风险是一个不容忽视的威胁。在本文中，我们回顾了目前关于棉铃虫（Helicoverpa armigerd）对Bt毒素Cry1Ac和Cry2Ab的抗性以及这些毒素之间相互关系的研究（包括基于蛋白质结合位点和抗性基因分析的研究）。在现有证据的基础上，我们假设Cry1Ac和Cry2Ab对棉铃虫的作用不是完全独立的，进而提出“抗性相关基因突变潜力假说”。尽管害虫对 Bt 毒素产生抗性的机制尚未得到全面阐明，但这一假设无疑对未来采用“金字塔”策略具有重要意义。建议进一步研究以制定策略来阻止棉铃虫对 Bt 棉花的抗性发展，