Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, 430070, China.
Department of Entomology, Nanjing Agricultural University, Nanjing, 210095, China.
Sci Rep. 2017 Jul 20;7(1):5992. doi: 10.1038/s41598-017-05110-9.
Bacillus thuringiensis (Bt) Cry toxins play an important role in the management of insect pests. Resistance to Bt toxins has been reported in many pest insects but the mechanism responsible for this resistance in rice crop pests remains largely unknown. Cadherin is one of several Bt toxin receptors. At present, only one cadherin gene, CsCAD1, has been documented in the striped rice stem borer, Chilo suppressalis. We amplified a nearly full-length transcript of another C. suppressalis cadherin gene, CsCAD2, and found that it has a different expression pattern to CsCAD1. CsCAD1 was highly expressed in fifth and sixth instar larvae, especially in the midgut, while the expression levels of CsCA2 were equably in each developmental stage. Newly hatched larvae were fed on rice smeared with synthesized siRNA to knockdown either CsCAD1 or CsCAD2, and then were fed transgenic rice expressing either the Cry2A or Cry1C toxins. The siRNA-treatment groups had lower mortality and higher survival rates than the control group, suggesting that reduced expression of CsCAD1 or CsCAD2 increased resistance to Cry2A and Cry1C. We conclude that CsCAD1 and CsCAD2 interact with Bt toxins in C. suppressalis and that this interaction could be the mechanism underlying Bt resistance in this insect.
苏云金芽孢杆菌（Bt）Cry 毒素在害虫管理中起着重要作用。许多害虫对 Bt 毒素产生了抗性，但在水稻作物害虫中导致这种抗性的机制在很大程度上仍然未知。钙黏蛋白是几种 Bt 毒素受体之一。目前，在二化螟中仅记录了一个钙黏蛋白基因 CsCAD1。我们扩增了另一个二化螟钙黏蛋白基因 CsCAD2 的近乎全长转录本，发现其表达模式与 CsCAD1 不同。CsCAD1 在五龄和六龄幼虫中高度表达，特别是在中肠，而 CsCA2 的表达水平在每个发育阶段都均匀。新孵化的幼虫用涂抹有合成 siRNA 的水稻喂食以敲低 CsCAD1 或 CsCAD2，然后用表达 Cry2A 或 Cry1C 毒素的转基因水稻喂食。siRNA 处理组的死亡率低于对照组，存活率高于对照组，这表明 CsCAD1 或 CsCAD2 的表达减少增加了对 Cry2A 和 Cry1C 的抗性。我们得出结论，CsCAD1 和 CsCAD2 与二化螟中的 Bt 毒素相互作用，这种相互作用可能是该昆虫对 Bt 产生抗性的机制。
