APN3 Acts as a Functional Receptor of Bacillus thuringiensis Cry1Ac in Grapholita molesta

Grapholita molesta (Busck) (Lepidoptera: Tortricidae) is a worldwide Rosaceae fruit tree pest. Although the Bacillus thuringiensis (Bt) Cry1Ac proteins exhibit excellent insecticidal activity against G. molesta, there are no reported Bt receptors for G. molesta. In the preliminary screening, we identified aminopeptidase N3 (GmolAPN3) as a potential receptor for Cry1Ac in G. molesta. Ligand blot and homologous competition experiments confirmed the simultaneous binding of interaction domains 2 (GluZincin superfamily domain) and 4 (ERAP1-C domain) of GmolAPN3 to activated Cry1Ac. In the cell toxicity bioassay, the overexpression of GmolAPN3 rendered Sf9 cells more susceptible to activated Cry1Ac. The results from dsRNA interference demonstrated that knockdown of GmolAPN3 conferred resistance in G. molesta larvae against Cry1Ac. Our findings provide pioneering evidence for the role of GmolAPN3 as the first identified Bt receptor mediating both binding and toxicity of Cry1Ac in G. molesta and also offer theoretical guidance for understanding the mode of action of Cry1Ac in G. molesta and its field applications.