Departamento de Fitotecnia, Universidade Federal de Viçosa, Viçosa, Minas, Gerais, 36570-900, Brazil.
Departamento de Biologia Geral, Universidade Federal de Viçosa, Viçosa, Minas Gerais, 36570-900, Brazil.
Sci Rep. 2019 Apr 30;9(1):6667. doi: 10.1038/s41598-019-43074-0.
Bioinsecticides and transgenic plants, based on Bacillus thuringiensis (Bt) toxins are important when managing Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae), a soybean defoliator pest. The interaction of these toxins with the caterpillar's midgut cells determines their efficacy as an insecticide. The objective was to evaluate the toxicity of B. thuringiensis, subsp. kurstaki strain HD-1 and cytopathological changes mediated by these bacterial toxins in the midgut of A. gemmatalis caterpillars. Insecticidal efficacy was determined by calculating lethal concentration values (LC, LC, LC, LC and LC) in the laboratory. Midgut fragments from A. gemmatalis were extracted after bacterial ingestion and evaluated by light, transmission electron and confocal microscopy. The Bt median lethal concentrations showed toxicity [LC = 0.46 (0.43-0.49) mg mL] to fourth instar A. gemmatalis caterpillars after 108 hours. Bt induces severe cytotoxicity to A. gemmatalis midgut epithelial cells with increasing exposure over time, causing cellular disorganization, microvillus degeneration, cell fragmentation and protrusion, peritrophic membrane rupture, and cell vacuolization. The cell nuclei presented condensed chromatin and an increase in lysosome numbers. Apoptosis occurred in the midgut cells of caterpillars exposed to Bt. A regenerative response in A. gemmatalis caterpillars was observed 8 hours after exposure to Bt, however this response was not continuous. Toxins produced by Bt are harmful to A. gemmatalis at median concentration with structural damage and death of the midgut epithelial cells of this insect.
苏云金芽孢杆菌（Bt）毒素的生物杀虫剂和转基因植物在防治大豆食心叶甲（鳞翅目：夜蛾科）这一大豆食叶害虫方面具有重要作用。这些毒素与毛毛虫中肠细胞的相互作用决定了它们作为杀虫剂的功效。本研究的目的是评估苏云金芽孢杆菌亚种 kurstaki 株 HD-1 对 A. gemmatalis 毛毛虫的毒性及其细菌毒素引起的细胞病变。通过在实验室中计算致死浓度值（LC、LC、LC、LC 和 LC）来确定杀虫效力。在细菌摄入后提取 A. gemmatalis 的中肠片段，并通过光镜、透射电子显微镜和共聚焦显微镜进行评估。Bt 的半数致死浓度对第 4 龄 A. gemmatalis 毛毛虫表现出毒性[LC = 0.46（0.43-0.49）mg mL]，108 小时后。Bt 随时间的延长对 A. gemmatalis 中肠上皮细胞产生严重的细胞毒性，导致细胞结构紊乱、微绒毛退化、细胞碎片化和突起、围食膜破裂和细胞空泡化。细胞核呈现浓缩染色质和溶酶体数量增加。暴露于 Bt 的毛毛虫中发生了细胞凋亡。暴露于 Bt 8 小时后观察到 A. gemmatalis 毛毛虫出现再生反应，但这种反应并非连续的。Bt 产生的毒素对 A. gemmatalis 具有中等浓度的危害性，导致该昆虫中肠上皮细胞结构受损和死亡。
