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Insect Biochem Mol Biol. 2018 Sep;100:59-65. doi: 10.1016/j.ibmb.2018.06.004. Epub 2018 Jun 30.

A single amino acid polymorphism in ABCC2 loop 1 is responsible for differential toxicity of Bacillus thuringiensis Cry1Ac toxin in different Spodoptera (Noctuidae) species.

Author information

1
Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China.
2
Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, 518120, China.
3
State Key Laboratory for Biology of Plant Disease and Insect Pests, Chinese Academy of Agricultural Sciences, West Yuanmingyuan Road, Beijing, 100193, China.
4
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, 62250, Morelos, Mexico.
5
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3, Cuernavaca, 62250, Morelos, Mexico. Electronic address: bravo@ibt.unam.mx.
6
Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China. Electronic address: yongboyang@mail.ccnu.edu.cn.
7
Institute of Entomology, School of Life Sciences, Central China Normal University, Wuhan, 430079, China. Electronic address: liukaiyu@mail.ccnu.edu.cn.

Abstract

Bacillus thuringiensis Cry toxins exert their toxicity by forming membrane pores after binding with larval midgut membrane proteins known as receptors. Spodoptera litura and Spodoptera frugiperda belong to the same genus, but S. litura is tolerant to Cry1Ac, while S. frugiperda is susceptible. The mechanism involved in the differential toxicity of Cry1Ac to these insect species is not understood. Amino acid sequences analysis of ABCC2, a well-recognized Cry1Ac receptor, from both species showed high sequence identity. Hi5 insect cells expressing SfABCC2 from S. frugiperda were 65-fold more susceptible than those expressing the SlABCC2 from S. litura. Substitution of fragments, point mutations and deletions between the ABCC2 of the two species revealed that ABCC2 amino acid Q125 from SfABCC2 or E125 from SlABCC2 was key factor for the differential Cry1Ac toxicity to Hi5 cells expressing these receptors. Consistently with this, cells expressing Helicoverpa armigera HaABCC2Q122-GFP, were more susceptible to Cry1Ac than cells expressing HaABCC2E122-GFP mutant. Q125 or E125 is located in a predicted exposed loop 1 region of ABCC2 indicating that this region could be important for Cry1Ac binding. These findings identified a single amino acid residue located in loop 1 of ABCC2 transporter as responsible for the different levels of susceptibility to Cry1Ac among various lepidopteran species.

KEYWORDS:

ABCC2 transporter; Bacillus thuringiensis; Cry toxin-resistance; Helicoverpa armigera; Spodoptera frugiperda; Spodoptera litura

PMID:
29964167
DOI:
10.1016/j.ibmb.2018.06.004
[Indexed for MEDLINE]

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