Enhancement of Bacillus thuringiensis toxicity by feeding Spodoptera littoralis larvae with bacteria expressing immune suppressive dsRNA
Enhancement of Bacillus thuringiensis toxicity by feeding Spodoptera littoralis larvae with bacteria expressing immune suppressive dsRNA
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DOI：
10.1007/s10340-019-01140-6
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发表时间：
2020-01-01
影响因子：
4.8
通讯作者：
Pennacchio, F.
中科院分区：
文献类型：
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作者：
Caccia, S.;Astarita, F.;Pennacchio, F.
用于昆虫害虫控制的RNAi干扰（RNAi）通常用于沉默控制重要功能的基因，从而产生致死表型。在这里，我们提出了一种新的方法，基于敲除免疫基因的dsRNA表达细菌作为一种策略，以提高喷雾应用的昆虫病原体苏云金芽孢杆菌（Bt）的影响。目的基因S1102控制斜纹夜蛾（Spodoptera littoralis）（鳞翅目，夜蛾科）的包囊和包囊化反应。为了递送S1102 dsRNA，我们已经开发了使用HT 115大肠杆菌的细菌表达系统。这使得dsRNA的生产成本更低，并保护其免受降解。通过人工饲料施用的转化细菌（dsRNA-Bac）被证明比体外合成的dsRNA更有效，无论是在基因沉默还是免疫抑制方面。这可能是dsRNA环境降解减少及其在肠道恶劣条件下受保护释放的结果。双链RNA-Bac与Bt生物农药Xentari（TM）联合口服与人工饲料联合施用，导致Bt对S4和5龄幼虫的杀灭活性显著增强。littoralis，无论是当两种成分同时施用或当基因沉默时，获得Bt暴露前。这些结果为开发含有杀死的dsRNA-Bac的新型Bt喷雾剂铺平了道路，这种喷雾剂通过抑制昆虫免疫反应来协同作用Bt毒素。这一战略将保持以Bt为基础的产品的长期功效，原则上可以提高昆虫天然拮抗剂提供的生态服务。
RNAi interference (RNAi) for insect pest control is often used to silence genes controlling vital functions, thus generating lethal phenotypes. Here, we propose a novel approach, based on the knockout of an immune gene by dsRNA-expressing bacteria as a strategy to enhance the impact of spray applications of the entomopathogen Bacillus thuringiensis (Bt). The target gene, Sl 102, controls the encapsulation and nodulation responses in the noctuid moth Spodoptera littoralis (Lepidoptera, Noctuidae). To deliver Sl 102 dsRNA, we have developed a bacterial expression system, using HT115 Escherichia coli. This allows a much cheaper production of dsRNA and its protection against degradation. Transformed bacteria (dsRNA-Bac) administered through artificial diet proved to be more effective than dsRNA synthesized in vitro, both in terms of gene silencing and immunosuppression. This is a likely consequence of reduced dsRNA environmental degradation and of its protected release in the harsh conditions of the gut. The combined oral administration with artificial diet of dsRNA-Bac and of a Bt-based biopesticide (Xentari (TM)) resulted in a remarkable enhancement of Bt killing activity, both on 4th and 5th instar larvae of S. littoralis, either when the two components were simultaneously administered or when gene silencing was obtained before Bt exposure. These results pave the way toward the development of novel Bt spray formulations containing killed dsRNA-Bac, which synergize Bt toxins by suppressing the insect immune response. This strategy will preserve the long-term efficacy of Bt-based products and can, in principle, enhance the ecological services provided by insect natural antagonists.