Cry2Ab receptor ABCA2 is a counter defense gene to protect corn ear worm against plant allelochemicals

Genetically engineered crops pyramided with insecticidal proteins Cry1Ac, Cry2Ab and Vip3A from
Bacillus thuringiensis (Bt) are widely used to manage some economically important pests including the corn earworm

Helicoverpa zea. Bt toxins Cry1Ac and Cry2Ab are known to kill pests at least partially through binding and disrupting the normal functions of some ATP-binding cassette (ABC) transporter protein such as ABCC2 targeted by Cry1Ac and ABCA2 targeted by Cry2Ab. Yet, the normal functions of these ABC transporters remain largely elusive in insects. To reveal the normal functions of the Cry2Ab receptor ABCA2, we used CRISPR/Cas9 gene editing technology to knock out H. zea ABCA2 (HzABCA2) gene and compared the susceptibilities of the resulted ABCA2 knockout strain with its parental susceptible strain to Cry2Ab and a broad range of plant defense allelochemicals naturally encountered by this pest. Knocking out ABCA2 caused >200-fold resistance to Cry2Ab while making the corn earworm more susceptible to multiple allelochemicals and resistant to one allelochemicals. The results demonstrate that the main normal function of HzABCA2 is to transport plant allelochemicals out of insect cells, counteracting plant chemical defenses.