Mining of Bt insecticidal protein receptors from the soybean looper genome with special reference to ABC transporters

Soybean looper (Chrysodeixis includens) is a lepidopteran pest primarily found in North and South America. Soybean looper feeds on soybeans, corn, cotton, cereals, and vegetables. The control of soybean looper largely relies on insecticides and transgenic crops, e.g., Bt (Bacillus thuringiensis) transgenic soybean expressing Cry1 insecticidal proteins such as Cry1Ac. Activated Bt Cry1 proteins bind to receptor proteins on the extracellular matrix of lepidopteran midgut epithelial cells, mediating oligomerization and subsequently pore formation by membrane insertion, leading to the death of the targeted pest. There is an emerging body of evidence that , in particular, ABC transporters such as ABCC2 act as Bt Cry protein receptors and mediate pore formation. There have been no reports of field resistance against Cry1Ac in soybean looper yet. This study focuses on the annotation, diversity, and role of ABC transporters and other Bt Cry1 protein receptors (such as cadherins, alkaline ,and aminopeptidases) potentially involved in Cry1Ac susceptibility in soybean loopers. Although their roles have not yet been well investigated, soybean looper has two duplicated ABCC2 genes and numerous other ABCC transporters such as ABCC3 that may serve as potential Cry1Ac receptors. Understanding how ABCC transporters influence Cry1Ac susceptibility and resistance is critical for developing strategies to prolong the efficacy of Bt crops and resistance management.