An ABC transporter mutation is correlated with insect resistance to Bacillus thuringiensis Cry1Ac toxin.
An ABC transporter mutation is correlated with insect resistance to Bacillus thuringiensis Cry1Ac toxin.
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DOI：
10.1371/journal.pgen.1001248
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发表时间：
2010-12-16
期刊：
影响因子：
4.5
通讯作者：
Heckel DG
中科院分区：
文献类型：
--
作者：
Gahan LJ;Pauchet Y;Vogel H;Heckel DG
从苏云金芽孢杆菌（Bt）中产生杀虫毒素的转基因作物在减少害虫危害方面取得了商业上的成功，但对威胁其可持续性的抗性机制的了解尚不完整。昆虫对形成孔的Cry1Ac毒素的抗性与失去与中肠膜的高亲和力、不可逆结合有关，但导致这种变化的遗传因素一直难以捉摸。在体外实验中，12-钙粘蛋白结构域蛋白的突变赋予一些Cry1Ac抗性，但不阻断这种毒素的结合。我们试图确定其他基因中的突变，这些突变可能是导致结合丧失的原因。本研究采用基于图谱的克隆方法，通过对1060个后代进行回交，鉴定了棉花害虫Heliothis virescens的抗性基因，该基因与钙粘蛋白突变独立分离。我们发现了ABC转运体ABCC2的失活突变，该突变与Cry1Ac抗性遗传相关，并与Cry1Ac与膜囊泡结合的丧失相关。ABC蛋白是一种完整的膜蛋白，具有多种功能，包括从细胞中输出有毒分子，但以前没有涉及到Bt毒素的作用模式。失活突变导致毒素结合减少，表明ABCC2参与了毒素孔的膜整合。我们的研究结果表明，ABC蛋白可能在Bt毒素的作用模式中发挥关键作用，并且ABC蛋白突变可以赋予高水平的抗性，这可能威胁到表达Bt的作物的持续利用。然而，这种突变可能通过减少细胞中其他毒素（如植物次生化合物）的输出，对抗性昆虫施加生理代价。可以利用这一弱点在田间管理这种Bt抗性机制。苏云金芽孢杆菌（Bacillus thuringiensis, Bt）的晶体毒素蛋白对某些昆虫具有高效力，而对大多数其他物种缺乏活性，是理想的生物杀虫剂。表达Cry1A bt毒素的转基因棉花和玉米目前已广泛应用于农业，从而大大减少了化学杀虫剂的使用。然而，这大大增加了害虫种群对毒素抗性的选择压力。预防或延缓这种耐药性的发展是一个高度优先事项，以避免因依赖化学农药而导致的杀虫剂耐药性的重演。由于Bt作用模式的分子细节尚不完全清楚，从田间收集并在实验室中选择具有高抗性的昆虫菌株，有助于发现毒素在最终形成孔并杀死昆虫之前必须克服的障碍。我们使用遗传方法来探索毒素作用模式中一个鲜为人知的步骤，该步骤在一种重要棉花害虫的极抗性菌株中被阻断。这一发现不仅提供了在实地出现这类耐药性时进行诊断的工具，还提出了可能抵消其最终传播的因素。
Transgenic crops producing insecticidal toxins from Bacillus thuringiensis (Bt) are commercially successful in reducing pest damage, yet knowledge of resistance mechanisms that threaten their sustainability is incomplete. Insect resistance to the pore-forming Cry1Ac toxin is correlated with the loss of high-affinity, irreversible binding to the mid-gut membrane, but the genetic factors responsible for this change have been elusive. Mutations in a 12-cadherin-domain protein confer some Cry1Ac resistance but do not block this toxin binding in in vitro assays. We sought to identify mutations in other genes that might be responsible for the loss of binding. We employed a map-based cloning approach using a series of backcrosses with 1,060 progeny to identify a resistance gene in the cotton pest Heliothis virescens that segregated independently from the cadherin mutation. We found an inactivating mutation of the ABC transporter ABCC2 that is genetically linked to Cry1Ac resistance and is correlated with loss of Cry1Ac binding to membrane vesicles. ABC proteins are integral membrane proteins with many functions, including export of toxic molecules from the cell, but have not been implicated in the mode of action of Bt toxins before. The reduction in toxin binding due to the inactivating mutation suggests that ABCC2 is involved in membrane integration of the toxin pore. Our findings suggest that ABC proteins may play a key role in the mode of action of Bt toxins and that ABC protein mutations can confer high levels of resistance that could threaten the continued utilization of Bt–expressing crops. However, such mutations may impose a physiological cost on resistant insects, by reducing export of other toxins such as plant secondary compounds from the cell. This weakness could be exploited to manage this mechanism of Bt resistance in the field. Crystal toxin proteins from Bacillus thuringiensis (Bt) make ideal bioinsecticides because of their high potency against certain insects and lack of activity against most other species. Transgenic cotton and maize expressing pore-forming Cry1A Bt-toxins are now widely used in agriculture, enabling substantial reductions in the use of chemical insecticides. However this has greatly increased the selection pressure in pest populations for toxin resistance. Preventing or delaying the development of this resistance is a high priority, to avoid a replay of the onset of insecticide resistance brought on by dependency on chemical pesticides. Because the molecular details of Bt mode of action are still not fully understood, insect strains collected from the field and selected to high levels of resistance in the laboratory are useful in discovering the obstacles the toxin must overcome before it finally forms the pore and kills the insect. We used a genetic approach to explore a poorly understood step in the toxin mode of action, which is blocked in an extremely resistant strain of an important cotton pest. As well as providing the tools to diagnose this type of resistance when it appears in the field, this discovery suggests factors that may counteract its eventual spread.
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影响因子：
11.4
作者：
Gaudet, R;Wiley, DC
通讯作者：
Wiley, DC
DOI：
10.1126/science.1168750
发表时间：
2009-03-27
期刊：
Science (New York, N.Y.)
影响因子：
--
作者：
Aller SG;Yu J;Ward A;Weng Y;Chittaboina S;Zhuo R;Harrell PM;Trinh YT;Zhang Q;Urbatsch IL;Chang G
通讯作者：
Chang G
影响因子：
14.9
作者：
Käll L;Krogh A;Sonnhammer EL
通讯作者：
Sonnhammer EL
影响因子：
6.7
作者：
Bellier A;Chen CS;Kao CY;Cinar HN;Aroian RV
通讯作者：
Aroian RV
影响因子：
4.1
作者：
Carrière Y;Crowder DW;Tabashnik BE
通讯作者：
Tabashnik BE