Departamento de Genética, Universitat de València, Burjassot, Spain.
PLoS One. 2013 Jul 5;8(7):e68164. doi: 10.1371/journal.pone.0068164. Print 2013.
First generation of insect-protected transgenic corn (Bt-corn) was based on the expression of Cry1Ab or Cry1Fa proteins. Currently, the trend is the combination of two or more genes expressing proteins that bind to different targets. In addition to broadening the spectrum of action, this strategy helps to delay the evolution of resistance in exposed insect populations. One of such examples is the combination of Cry1A.105 with Cry1Fa and Cry2Ab to control O. nubilalis and S. frugiperda. Cry1A.105 is a chimeric protein with domains I and II and the C-terminal half of the protein from Cry1Ac, and domain III almost identical to Cry1Fa. The aim of the present study was to determine whether the chimeric Cry1A.105 has shared binding sites either with Cry1A proteins, with Cry1Fa, or with both, in O. nubilalis and in S. frugiperda. Brush-border membrane vesicles (BBMV) from last instar larval midguts were used in competition binding assays with (125)I-labeled Cry1A.105, Cry1Ab, and Cry1Fa, and unlabeled Cry1A.105, Cry1Aa, Cry1Ab, Cry1Ac, Cry1Fa, Cry2Ab and Cry2Ae. The results showed that Cry1A.105, Cry1Ab, Cry1Ac and Cry1Fa competed with high affinity for the same binding sites in both insect species. However, Cry2Ab and Cry2Ae did not compete for the binding sites of Cry1 proteins. Therefore, according to our results, the development of cross-resistance among Cry1Ab/Ac, Cry1A.105, and Cry1Fa proteins is possible in these two insect species if the alteration of shared binding sites occurs. Conversely, cross-resistance between these proteins and Cry2A proteins is very unlikely in such case.
第一代抗虫转基因玉米（Bt 玉米）基于 Cry1Ab 或 Cry1Fa 蛋白的表达。目前，趋势是结合表达结合不同靶标的蛋白的两个或更多基因。除了拓宽作用谱外，该策略还有助于延缓暴露昆虫种群中抗性的进化。其中一个例子是将 Cry1A.105 与 Cry1Fa 和 Cry2Ab 结合，以控制 O. nubilalis 和 S. frugiperda。Cry1A.105 是一种嵌合蛋白，具有 Cry1Ac 的 I 域和 II 域以及蛋白的 C 端一半，以及与 Cry1Fa 几乎相同的 III 域。本研究旨在确定嵌合 Cry1A.105 是否与 O. nubilalis 和 S. frugiperda 中的 Cry1A 蛋白、Cry1Fa 或两者都具有共同的结合位点。使用来自最后龄幼虫中肠的刷状缘膜泡（BBMV）在竞争结合测定中与（125）I 标记的 Cry1A.105、Cry1Ab 和 Cry1Fa 以及未标记的 Cry1A.105、Cry1Aa、Cry1Ab、Cry1Ac、Cry1Fa、Cry2Ab 和 Cry2Ae 进行竞争。结果表明，Cry1A.105、Cry1Ab、Cry1Ac 和 Cry1Fa 以高亲和力竞争两种昆虫中相同的结合位点。然而，Cry2Ab 和 Cry2Ae 不竞争 Cry1 蛋白的结合位点。因此，根据我们的结果，如果发生共享结合位点的改变，Cry1Ab/Ac、Cry1A.105 和 Cry1Fa 蛋白在这两种昆虫中可能会发生交叉抗性。相反，在这种情况下，这些蛋白与 Cry2A 蛋白之间不太可能发生交叉抗性。
