PDF(Pubmed)
Abstract：
Bacillus thuringiensis (Bt) secretes the nutritional insecticidal protein Vip3Aa11, which exhibits high toxicity against the fall armyworm (Spodoptera frugiperda). The Bt HD270 extracellular polysaccharide (EPS) enhances the toxicity of Vip3Aa11 protoxin against S. frugiperda by enhancing the attachment of brush border membrane vesicles (BBMVs). However, how EPS-HD270 interacts with Vip3Aa11 protoxin in vivo and the effect of EPS-HD270 on the toxicity of activated Vip3Aa11 toxin are not yet clear. Our results indicated that there is an interaction between mannose, a monosaccharide that composes EPS-HD270, and Vip3Aa11 protoxin, with a dissociation constant of Kd = 16.75 ± 0.95 mmol/L. When EPS-HD270 and Vip3Aa11 protoxin were simultaneously fed to third-instar larvae, laser confocal microscopy observations revealed the co-localization of the two compounds near the midgut wall, which aggravated the damage to BBMVs. EPS-HD270 did not have a synergistic insecticidal effect on the activated Vip3Aa11 protein against S. frugiperda. The activated Vip3Aa11 toxin demonstrated a significantly reduced binding capacity (548.73 ± 82.87 nmol/L) towards EPS-HD270 in comparison to the protoxin (34.96 ± 9.00 nmol/L). Furthermore, this activation diminished the affinity of EPS-HD270 for BBMVs. This study provides important evidence for further elucidating the synergistic insecticidal mechanism between extracellular polysaccharides and Vip3Aa11 protein both in vivo and in vitro.
摘要：
苏云金芽孢杆菌（Bt）分泌营养杀虫蛋白Vip3Aa11，对秋季粘虫（Spodopterafrugiperda）具有高毒性。BtHD270胞外多糖（EPS）通过增强刷状缘膜囊泡（BBMV）的附着来增强Vip3Aa11原毒素对水果链球菌的毒性。然而,EPS-HD270在体内如何与Vip3Aa11原毒素相互作用以及EPS-HD270对激活的Vip3Aa11毒素毒性的影响尚不清楚。我们的结果表明，甘露糖之间存在相互作用，组成EPS-HD270和Vip3Aa11原毒素的单糖，解离常数Kd=16.75±0.95mmol/L当EPS-HD270和Vip3Aa11原毒素同时饲喂三龄幼虫时，激光共聚焦显微镜观察显示两种化合物在中肠壁附近的共定位，这加剧了对BBMV的损害。EPS-HD270对活化的Vip3Aa11蛋白对水果链球菌没有协同杀虫作用。与前毒素（34.96±9.00nmol/L）相比，活化的Vip3Aa11毒素对EPS-HD270的结合能力（548.73±82.87nmol/L）显着降低。此外，这种激活降低了EPS-HD270对BBMV的亲和力。本研究为进一步阐明胞外多糖与Vip3Aa11蛋白在体内和体外的协同杀虫机制提供了重要证据。
