Different Effects of Bacillus thuringiensis Toxin Cry1Ab on Midgut Cell Transmembrane Potential of Mythimna separata and Agrotis ipsilon Larvae

Toxins

Yingying Wang¹  Zhaonong Hu¹  Wenjun Wu¹ 

[1] Institute of Pesticide Science, College of Plant Protection, Northwest A & F University, Yangling 712100, Shaanxi, China;

关键词: Bacillus thuringiensis;    Cry1Ab;    Mythimna separata;    Agrotis ipsilon;    apical membrane potential;    sensitivity;   

DOI  :  10.3390/toxins7124894

来源: mdpi

【 摘 要 】

Bacillus thuringiensis (Bt) Cry toxins from the Cry1A family demonstrate significantly different toxicities against members of the family Noctuidae for unknown reasons. In this study, membrane potential was measured and analyzed in freshly isolated midgut samples from Mythimna separata and Agrotis ipsilon larvae under oral administration and in vitro incubation with Bt toxin Cry1Ab to elucidate the mechanism of action for further control of these pests. Bioassay results showed that the larvae of M. separata achieved a LD₅₀ of 258.84 ng/larva at 24 h after ingestion; M. separata larvae were at least eightfold more sensitive than A. ipsilon larvae to Cry1Ab. Force-feeding showed that the observed midgut apical-membrane potential (V_am) of M. separata larvae was significantly depolarized from −82.9 ± 6.6 mV to −19.9 ± 7.2 mV at 8 h after ingestion of 1 μg activated Cry1Ab, whereas no obvious changes were detected in A. ipsilon larvae with dosage of 5 μg Cry1Ab. The activated Cry1Ab caused a distinct concentration-dependent depolarization of the apical membrane; V_am was reduced by 50% after 14.7 ± 0.2, 9.8 ± 0.4, and 7.6 ± 0.6 min of treatment with 1, 5, and 10 μg/mL Cry1Ab, respectively. Cry1Ab showed a minimal effect on A. ipsilon larvae even at 20 μg/mL, and V_am decreased by 26.3% ± 2.3% after 15 min. The concentrations of Cry1Ab displayed no significant effect on the basolateral side of the epithelium. The V_am of A. ipsilon (−33.19 ± 6.29 mV, n = 51) was only half that of M. separata (−80.94 ± 6.95 mV, n = 75). The different degrees of sensitivity to Cry1Ab were speculatively associated with various habits, as well as the diverse physiological or biochemical characteristics of the midgut cell membranes.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.