四种Bt毒素蛋白对二点委夜蛾幼虫毒力测定及中肠组织病理学变化

为更好地了解苏云金芽胞杆菌Bacillus thuringiensis毒素蛋白对二点委夜蛾Athetis lepigone的毒力以及作用机理,通过饲喂含有Cry1Ac、Cry1Ab、Cry2Ab和Vip3Aa四种不同Bt毒素蛋白饲料,测定Bt毒素蛋白对二点委夜蛾幼虫的毒力,并观察取食4种毒素蛋白后幼虫中肠组织的病理学变化。结果显示,二点委夜蛾幼虫取食毒素蛋白后72 h,Cry1Ab和Cry1Ac毒素蛋白对二点委夜蛾幼虫的杀虫活性较高,校正死亡率为84.7%和76.4%;Vip3Aa和Cry2Ab毒素蛋白的毒力较弱。二点委夜蛾幼虫取食4种Bt毒素蛋白后,中肠柱状细胞微绒毛脱落,杂乱地分散在肠腔内,杯状细胞变形和腔内微绒毛脱落,线粒体和内质网等变形破裂,细胞核的核膜消失、核质凝聚和形状发生变化,经Cry1Ab和Cry1Ac毒素蛋白处理后中肠细胞的病变症状和速度明显高于Cry2Ab和Vip3Aa毒素蛋白处理。表明Cry1Ab和Cry1Ac毒素蛋白对二点委夜蛾幼虫杀虫活性较高,显著高于Cry2Ab和Vip3Aa毒素蛋白,且对其中肠细胞的破坏作用也较强。

Toxicity of Bacillus thuringiensis toxin proteins against Athetis lepigone larvae and histopathology of the midgut of the larvae

In order to examine the action mechanism of Bacillus thuringiensis toxin against Athetis lepigone larvae, A. lepigone larvae were fed on Cry1Ac, Cry1Ab, Cry2Ab and Vip3A toxins, and the toxicity of Bt toxin proteins to A. lepigone larvae was detected, and the cellular morphological change in the midgut of larvae was observed by transmission electron microscope (TEM). The results showed that Cry1Ab and Cry1Ac toxins had higher toxicity against the larvae of A. lepigone than Cry2Ab and Vip3Aa toxins, and the corrected mortality were 84.7% and 76.4%, respectively. Obvious histopathological changes were observed in the midgut cells after the larvae were fed on Bt toxins. Microvillis of column cells and goblet cells dropped off. Mitochondria and endoplasmic reticulum were dissolved and mixed disorderly. Wiredraw of nucleus, condensation of nuclear, and disappearance of nuclear membrane were also observed. The pathological changes of column cells and goblet cells in the midgut of A. lepigone larvae induced by Vip3Aa and Cry2Ab were slower than that by Cry1Ab and Cry1Ac. The results indicated that Cry1Ab and Cry1Ac toxins had higher toxicity against the larvae of A. lepigone than Vip3Aa and Cry2Ab toxins. Similar to the changes of histopathology, Cry1Ab and Cry1Ac toxins disrupted the midgut epithelium cells faster than Vip3Aa and Cry2Ab toxins. Lysis of gut epithelium cells resulting in larval death might be the mode of action of Cry toxin and Vip toxin.