Hubei Insect Resources Utilization and Sustainable Pest Management Key Laboratory, College of Plant Science and Technology, Huazhong Agricultural University, Wuhan 430070, People's Republic of China.
Sci Rep. 2017 Jan 9;7:40222. doi: 10.1038/srep40222.
The bacterium Bacillus thuringiensis produces Crystal (Cry) proteins that are toxic to a diverse range of insects. Transgenic crops that produce Bt Cry proteins are grown worldwide because of their improved resistance to insect pests. Although Bt "pyramid" cotton that produces both Cry1A and Cry2A is predicted to be more resistant to several lepidopteran pests, including Spodoptera exigua, than plants that produce Cry1Ac alone, the mechanisms responsible for the toxicity of Cry2Aa in S. exigua are not well understood. We identified several proteins that bind Cry2Aa (polycalin, V-ATPase subunits A and B, actin, 4-hydroxybutyrate CoA-transferase [4-HB-CoAT]), and a receptor for activated protein kinase C (Rack), in S. exigua. Recombinant, expressed versions of these proteins were able to bind the Cry2Aa toxin in vitro assays. RNA interference gene knockdown of the Se-V-ATPase subunit B significantly decreased the susceptibility of S. exigua larvae to Cry2Aa, whereas knockdown of the other putative binding proteins did not. Moreover, an in vitro homologous competition assay demonstrated that the Se-V-ATPase subunit B binds specifically to the Cry2Aa toxin, suggesting that this protein acts as a functional receptor of Cry2Aa in S. exigua. This the first Cry2Aa toxin receptor identified in S. exigua brush-border membrane vesicles.
苏云金芽孢杆菌产生的 Crystal（Cry）蛋白对多种昆虫具有毒性。由于其对害虫的抗虫性提高，全世界都在种植生产 Bt Cry 蛋白的转基因作物。尽管预计同时生产 Cry1A 和 Cry2A 的 Bt“金字塔”棉花比单独生产 Cry1Ac 的植物对包括斜纹夜蛾在内的几种鳞翅目害虫更具抗性，但 Cry2Aa 在斜纹夜蛾中的毒性机制尚不清楚。我们在斜纹夜蛾中鉴定出几种与 Cry2Aa 结合的蛋白质（多钙蛋白、V-ATPase 亚基 A 和 B、肌动蛋白、4-羟基丁酸 CoA 转移酶[4-HB-CoAT]）和蛋白激酶 C 激活受体（Rack）。这些蛋白质的重组、表达形式能够在体外结合 Cry2Aa 毒素。Se-V-ATPase 亚基 B 的 RNA 干扰基因敲低显著降低了斜纹夜蛾幼虫对 Cry2Aa 的敏感性，而其他假定结合蛋白的敲低则没有。此外，体外同源竞争测定表明，Se-V-ATPase 亚基 B 特异性结合 Cry2Aa 毒素，表明该蛋白在斜纹夜蛾中作为 Cry2Aa 的功能受体发挥作用。这是在斜纹夜蛾刷状缘膜囊泡中鉴定出的第一个 Cry2Aa 毒素受体。
