A <i>cis</i>-Acting Mutation in the <i>Px</i><i>ABCG1</i> Promoter Is Associated with Cry1Ac Resistance in <i>Plutella xylostella</i> (L.)

• Main Authors: Jianying Qin, Fan Ye, Linzheng Xu, Xuguo Zhou, Neil Crickmore, Xiaomao Zhou, Youjun Zhang, Zhaojiang Guo
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>Bacillus thuringiensis</i>; <i>Plutella xylostella</i>; <i>cis</i>-mutation; Antp; ABCG1; Cry1Ac resistance
• Online Access: https://www.mdpi.com/1422-0067/22/11/6106

The molecular mechanisms of insect resistance to Cry toxins generated from the bacterium <i>Bacillus thuringiensis</i> (Bt) urgently need to be elucidated to enable the improvement and sustainability of Bt-based products. Although downregulation of the expression of midgut receptor genes is a pivotal mechanism of insect resistance to Bt Cry toxins, the underlying transcriptional regulation of these genes remains elusive. Herein, we unraveled the regulatory mechanism of the downregulation of the ABC transporter gene <i>PxABCG1</i> (also called <i>Pxwhite</i>), a functional midgut receptor of the Bt Cry1Ac toxin in <i>Plutella xylostella.</i> The <i>Px</i><i>ABCG1</i> promoters of Cry1Ac-susceptible and Cry1Ac-resistant strains were cloned and analyzed, and they showed clear differences in activity. Subsequently, a dual-luciferase reporter assay, a yeast one-hybrid (Y1H) assay, and RNA interference (RNAi) experiments demonstrated that a <i>cis</i>-mutation in a binding site of the Hox transcription factor Antennapedia (Antp) decreased the promoter activity of the resistant strain and eliminated the binding and regulation of Antp, thereby enhancing the resistance of <i>P. xylostella</i> to the Cry1Ac toxin. These results advance our knowledge of the roles of <i>cis</i>- and <i>trans</i>-regulatory variations in the regulation of midgut Cry receptor genes and the evolution of Bt resistance, contributing to a more complete understanding of the Bt resistance mechanism.