Independent and Synergistic Effects of Knocking out Two ABC Transporter Genes on Resistance to Bacillus thuringiensis Toxins Cry1Ac and Cry1Fa in Diamondback Moth.

Shan Zhao,Bruce E Tabashnik,Falong Wang,Yidong Wu,Dong Jiang,Yihua Yang

doi:10.3390/toxins13010009

Shan Zhao, Bruce E Tabashnik + Show 4 more

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https://doi.org/10.3390/toxins13010009

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Journal: Toxins	Publication Date: Dec 24, 2020
Citations: 21	License type: CC BY 4.0

Affiliation: University of Arizona, Nanjing Agricultural University

Abstract

Insecticidal proteins from Bacillus thuringiensis (Bt) are used widely in sprays and transgenic crops to control insect pests. However, evolution of resistance by pests can reduce the efficacy of Bt toxins. Here we analyzed resistance to Bt toxins Cry1Ac and Cry1Fa in the diamondback moth (Plutella xylostella), one of the world’s most destructive pests of vegetable crops. We used CRISPR/Cas9 gene editing to create strains with knockouts of the ATP-binding cassette (ABC) transporter genes PxABCC2, PxABCC3, or both. Bioassay results show that knocking out either gene alone caused at most 2.9-fold resistance but knocking out both caused >10,320-fold resistance to Cry1Ac and 380-fold resistance to Cry1Fa. Cry1Ac resistance in the double knockout strain was recessive and genetically linked with the PxABCC2/PxABCC3 loci. The results provide insight into the mechanism of cross-resistance to Cry1Fa in diamondback moth. They also confirm previous work with this pest showing that mutations disrupting both genes cause higher resistance to Cry1Ac than mutations affecting either PxABCC2 or PxABCC3 alone. Together with previous work, the results here highlight the value of using single and multiple gene knockouts to better understand the independent and synergistic effects of putative Bt toxin receptors on resistance to Bt toxins.

Highlights

Insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have been used widely in sprays since the 1920s and in transgenic crops since 1996 to control some key insect pests [1]
Resistance of diamondback moth to Cry1Ac caused by CRISPR-mediated deletions was >10,320-fold with both PxABCC2 and PxABCC3 knocked out, but only 2.9fold with knockout of PxABCC2 alone and 2.1-fold with knockout of PxABCC3 alone
These results imply that both PxABCC2 and PxABCC3 can affect the susceptibility of diamondback to Cry1Ac, consistent with findings of two previous studies [15,16]

Summary

Introduction

Insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have been used widely in sprays since the 1920s and in transgenic crops since 1996 to control some key insect pests [1]. Practical resistance to Bt toxins used in sprays and transgenic crops has been documented in some populations of at least 11 insect species [3,4,5,6,7]. We focus on resistance to Bt toxins in the diamondback moth (Plutella xylostella), one of the most destructive pests of cruciferous vegetables worldwide [8]. This pest causes economic losses up to 5 billion dollars annually [9] and has evolved resistance to all major classes of insecticides [3]. Transgenic Bt host plants of this pest have been produced for experimental purposes, but are not commercially available [3]

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Conclusion