USDA-ARS, Corn Insects & Crop Genetics Research Unit, 103 Genetics Laboratory, Iowa State University, Ames, IA, 50011, USA.
INRAE, CNRS, Université Côte d'Azur, ISA, France.
BMC Genomics. 2021 Sep 4;22(1):639. doi: 10.1186/s12864-021-07932-4.
Resistance of pest insect species to insecticides, including B. thuringiensis (Bt) pesticidal proteins expressed by transgenic plants, is a threat to global food security. Despite the western corn rootworm, Diabrotica virgifera virgifera, being a major pest of maize and having populations showing increasing levels of resistance to hybrids expressing Bt pesticidal proteins, the cell mechanisms leading to mortality are not fully understood.
Twenty unique RNA-seq libraries from the Bt susceptible D. v. virgifera inbred line Ped12, representing all growth stages and a range of different adult and larval exposures, were assembled into a reference transcriptome. Ten-day exposures of Ped12 larvae to transgenic Bt Cry3Bb1 and Gpp34/Tpp35Ab1 maize roots showed significant differential expression of 1055 and 1374 transcripts, respectively, compared to cohorts on non-Bt maize. Among these, 696 were differentially expressed in both Cry3Bb1 and Gpp34/Tpp35Ab1 maize exposures. Differentially-expressed transcripts encoded protein domains putatively involved in detoxification, metabolism, binding, and transport, were, in part, shared among transcripts that changed significantly following exposures to the entomopathogens Heterorhabditis bacteriophora and Metarhizium anisopliae. Differentially expressed transcripts in common between Bt and entomopathogen treatments encode proteins in general stress response pathways, including putative Bt binding receptors from the ATP binding cassette transporter superfamily. Putative caspases, pro- and anti-apoptotic factors, as well as endoplasmic reticulum (ER) stress-response factors were identified among transcripts uniquely up-regulated following exposure to either Bt protein.
Our study suggests that the up-regulation of genes involved in ER stress management and apoptotic progression may be important in determining cell fate following exposure of susceptible D. v. virgifera larvae to Bt maize roots. This study provides novel insights into insect response to Bt intoxication, and a possible framework for future investigations of resistance mechanisms.
包括转植物表达的苏云金芽孢杆菌（Bt）杀虫蛋白在内的杀虫剂，害虫物种的抗药性对全球粮食安全构成威胁。尽管西部玉米根虫（Diabrotica virgifera virgifera）是玉米的主要害虫，其种群对表达 Bt 杀虫蛋白的杂交种的抗性水平不断提高，但导致死亡的细胞机制尚不完全清楚。
组装了 Bt 敏感的 D. v. virgifera 近交系 Ped12 的 20 个独特的 RNA-seq 文库，代表了所有生长阶段以及一系列不同的成虫和幼虫暴露，构建了一个参考转录组。与对照玉米相比，10 天龄的 Ped12 幼虫暴露于转基因 Bt Cry3Bb1 和 Gpp34/Tpp35Ab1 玉米根中，分别有 1055 和 1374 个转录本的表达存在显著差异。其中，696 个转录本在 Cry3Bb1 和 Gpp34/Tpp35Ab1 玉米暴露中均有差异表达。差异表达的转录本编码的蛋白结构域可能参与解毒、代谢、结合和运输，部分与暴露于昆虫病原体异小杆线虫和金龟子绿僵菌后的转录本显著变化共享。Bt 和昆虫病原体处理之间共有的差异表达转录本编码一般应激反应途径中的蛋白，包括来自 ATP 结合盒转运蛋白超家族的假定 Bt 结合受体。在暴露于 Bt 蛋白后，唯一上调的转录本中鉴定出了假定的半胱天冬酶、促凋亡和抗凋亡因子以及内质网（ER）应激反应因子。
我们的研究表明，在易感性 D. v. virgifera 幼虫暴露于 Bt 玉米根后，参与 ER 应激管理和凋亡进程的基因的上调可能对决定细胞命运很重要。本研究为昆虫对 Bt 中毒的反应提供了新的见解，并为未来对抗性机制的研究提供了一个可能的框架。
