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首页> 外文期刊>Applied and Environmental Microbiology >Production and Characterization of Bacillus thuringiensis Cry1Ac-Resistant Cotton Bollworm Helicoverpa zea (Boddie)
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Production and Characterization of Bacillus thuringiensis Cry1Ac-Resistant Cotton Bollworm Helicoverpa zea (Boddie)

机译：苏云金芽孢杆菌抗Cry1Ac棉铃虫Helicoverpa zea（Boddie）的生产与鉴定

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摘要

Laboratory-selected Bacillus thuringiensis-resistant colonies are important tools for elucidating B. thuringiensis resistance mechanisms. However, cotton bollworm, Helicoverpa zea, a target pest of transgenic corn and cotton expressing B. thuringiensis Cry1Ac (Bt corn and cotton), has proven difficult to select for stable resistance. Two populations of H. zea (AR and MR), resistant to the B. thuringiensis protein found in all commercial Bt cotton varieties (Cry1Ac), were established by selection with Cry1Ac activated toxin (AR) or MVP II (MR). Cry1Ac toxin reflects the form ingested by H. zea when feeding on Bt cotton, whereas MVP II is a Cry1Ac formulation used for resistance selection and monitoring. The resistance ratio (RR) for AR exceeded 100-fold after 11 generations and has been maintained at this level for nine generations. This is the first report of stable Cry1Ac resistance in H. zea. MR crashed after 11 generations, reaching only an RR of 12. AR was only partially cross-resistant to MVP II, suggesting that MVP II does not have the same Cry1Ac selection pressure as Cry1Ac toxin against H. zea and that proteases may be involved with resistance. AR was highly cross-resistant to Cry1Ab toxin but only slightly cross-resistant to Cry1Ab expressing corn leaf powder. AR was not cross-resistant to Cry2Aa2, Cry2Ab2-expressing corn leaf powder, Vip3A, and cypermethrin. Toxin-binding assays showed no significant differences, indicating that resistance was not linked to a reduction in binding. These results aid in understanding why this pest has not evolved B. thuringiensis resistance, and highlight the need to choose carefully the form of B. thuringiensis protein used in experiments.
机译：实验室选择的苏云金芽孢杆菌抗性菌落是阐明苏云金芽孢杆菌抗性机制的重要工具。然而，已经证明难以选择棉铃虫Helicoverpa zea，其是表达苏云金芽孢杆菌Cry1Ac（Bt玉米和棉花）的转基因玉米和棉花的目标害虫，难以选择。通过选择Cry1Ac活化毒素（AR）或MVP II（MR），建立了两个对所有商业化的Bt棉花品种（Cry1Ac）中存在的苏云金芽孢杆菌蛋白具有抗性的玉米H. zea（AR和MR）种群。 Cry1Ac毒素反映了以Bt棉为食时H. zea摄入的形式，而MVP II是用于抗性选择和监测的Cry1Ac制剂。 11代后，AR的电阻率（RR）超过100倍，并在此水平上保持了9代。这是玉米中稳定的Cry1Ac抗性的首次报道。 MR在11代后崩溃，仅达到RR的12。AR仅对MVP II具有部分交叉抗性，这表明MVP II与针对H. zea的Cry1Ac毒素没有相同的Cry1Ac选择压力，并且蛋白酶可能与抵抗性。 AR对Cry1Ab毒素具有高度的交叉抗性，但对表达Cry1Ab的玉米叶粉仅具有轻微的交叉抗性。 AR对Cry2Aa2，表达Cry2Ab2的玉米叶粉，Vip3A和氯氰菊酯没有交叉抗性。毒素结合试验显示无显着差异，表明抗药性与结合减少无关。这些结果有助于理解为什么这种害虫没有进化出对苏云金芽孢杆菌的抗性，并强调需要仔细选择实验中使用的苏云金芽孢杆菌蛋白的形式。

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