CRISPR/Cas9-based functional characterization of PxABCB1 reveals its roles in the resistance of Plutella xylostella (L.) to Cry1Ac, abamectin and emamectin benzoate

The identification of functional midgut receptors for pesticidal proteins produced by Bacillus thuringiensis (Bt) is critical for deciphering the molecular mechanism of Bt resistance in insects. Reduced expression of the PxABCB1 gene was previously found to be associated with Cry1Ac resistance in the diamondback moth, Plutella xylostella (L.). To directly validate the potential receptor role of PxABCB1 and its contribution to Bt Cry1Ac toxicity in P. xylostella, we used CRISPR/Cas9 to generate a homozygous knockout ABCB1KO strain with a 5-bp deletion in exon 3 of its gene. The ABCB1KO strain exhibited a 63-fold resistance to Cry1Ac toxin compared to the parental DBM1Ac-S strain. Intriguingly, the ABCB1KO strain also exhibited significant increases in susceptibility to abamectin and emamectin benzoate. No changes in susceptibility to various other Bt Cry proteins or synthetic insecticides were observed. The knockout strain exhibited no significant fitness costs. Overall, our study indicates that PxABCB1 can protect the insect against avermectin insecticides on one hand, while on the other hand it facilitates the toxic effect of the Bt Cry1Ac toxin. The results of this study will help to inform integrated pest management approaches against this destructive pest.