ATP-Binding Cassette Subfamily A Member 2 is a Functional Receptor for Bacillus thuringiensis Cry2A Toxins in Bombyx mori, but not for Cry1A, Cry1C, Cry1D, Cry1F, or Cry9A Toxins.

Xiaoyi Li,Sanae Wada,Yoko Takasu,Kenji Watanabe,Tetsuya Iizuka,Kazuhisa Miyamoto,Ryoichi Sato,Satomi Adegawa

doi:10.3390/toxins12020104

Xiaoyi Li, Sanae Wada + Show 6 more

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https://doi.org/10.3390/toxins12020104

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Abstract

Cry toxins are insecticidal proteins produced by Bacillus thuringiensis (Bt). They are used commercially to control insect pests since they are very active in specific insects and are harmless to the environment and human health. The gene encoding ATP-binding cassette subfamily A member 2 (ABCA2) was identified in an analysis of Cry2A toxin resistance genes. However, we do not have direct evidence for the role of ABCA2 for Cry2A toxins or why Cry2A toxin resistance does not cross to other Cry toxins. Therefore, we performed two experiments. First, we edited the ABCA2 sequence in Bombyx mori using transcription activator-like effector-nucleases (TALENs) and confirmed the susceptibility-determining ability in a diet overlay bioassay. Strains with C-terminal half-deleted BmABCA2 showed strong and specific resistance to Cry2A toxins; even strains carrying a deletion of 1 to 3 amino acids showed resistance. However, the C-terminal half-deleted strains did not show cross-resistance to other toxins. Second, we conducted a cell swelling assay and confirmed the specific ability of BmABCA2 to Cry2A toxins in HEK239T cells. Those demonstrated that BmABCA2 is a functional receptor for Cry2A toxins and that BmABCA2 deficiency-dependent Cry2A resistance does not confer cross-resistance to Cry1A, Cry1Ca, Cry1Da, Cry1Fa or Cry9Aa toxins.

Highlights

Cry toxins are insecticidal crystal proteins and pore-forming toxins produced by Bacillus thuringiensis (Bt) [1,2]
Toxicity tests of the strains with C-terminal half-deleted BmABCA2 (A2T01, A2T06, and A2T14). Showed that they were highly resistant to Cry2Ab (Figure 2), indicating that BmABCA2 plays an essential role in determining the susceptibility of B. mori to Cry2Ab
ATP-binding cassette subfamily A member 2 (ABCA2) was first suggested to be linked to Cry2Ab resistance in H. armigera [20]

Summary

Introduction

Cry toxins are insecticidal crystal proteins and pore-forming toxins produced by Bacillus thuringiensis (Bt) [1,2]. Toxins 2020, 12, 104 interact with specific receptors on the columnar cell membrane [3]. This interaction drives the toxins to insert partial structures into the membrane, forming ion channels [4]. A cation influx triggers the influx of water [5], resulting in cell swelling and lysis [2,6]. Given their strong toxicity in specific species and inability to harm the environment and human health, Cry toxins are used widely in pest control [7]. Resistant insect strains have been found in these crops [9]

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