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Toxins 2015, 7(12), 5448-5458; doi:10.3390/toxins7124894

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

1
Institute of Pesticide Science, College of Plant Protection, Northwest A & F University, Yangling 712100, Shaanxi, China
2
Key Laboratory of Botanical Pesticide R & D in Shaanxi Province, Yangling 712100, Shaanxi, China
*
Author to whom correspondence should be addressed.
Academic Editor: Vernon L. Tesh
Received: 3 November 2015 / Revised: 23 November 2015 / Accepted: 9 December 2015 / Published: 15 December 2015
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Abstract

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 (Vam) 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; Vam 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 Vam 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 Vam 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. View Full-Text
Keywords: Bacillus thuringiensis; Cry1Ab; Mythimna separata; Agrotis ipsilon; apical membrane potential; sensitivity Bacillus thuringiensis; Cry1Ab; Mythimna separata; Agrotis ipsilon; apical membrane potential; sensitivity
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Wang, Y.; Hu, Z.; Wu, W. Different Effects of Bacillus thuringiensis Toxin Cry1Ab on Midgut Cell Transmembrane Potential of Mythimna separata and Agrotis ipsilon Larvae. Toxins 2015, 7, 5448-5458.

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