Editing the kinesin-12 gene affects responses to Bt toxin Cry1Ac in Helicoverpa zea

Crops genetically engineered to produce insecticidal proteins from Bacillus thuringiensis (Bt) are used globally to manage key insect pests. However, the evolution of resistance to Bt proteins in at least 11 pest species has reduced the effectiveness of Bt crops. Resistance to crystalline (Cry) Bt proteins including Cry1Ac produced by Bt cotton is a major problem in Helicoverpa zea (also known as bollworm and corn earworm), one of the most economically damaging pests in the United States. A previous genome-wide association study identified a nonsense point mutation in a kinesin-12 gene that was associated with resistance to Cry1Ac in a lab-selected strain of H. zea. Here, we used CRISPR/Cas9 gene editing to knock out the kinesin-12 gene in a Cry1Ac-susceptible laboratory strain, which caused a 4.0-fold increase in resistance to Cry1Ac. Conversely, gene editing that repaired the natural kinesin-12 nonsense mutation in a lab-selected resistant strain increased susceptibility to Cry1Ac by 3.8-fold. These complementary results provide compelling evidence that kinesin-12 plays a role in the mode of action of Cry1Ac against H. zea.