Identification and Characterization of Hyphantria cunea Aminopeptidase N as a Binding Protein of Bacillus thuringiensis Cry1Ab35 Toxin.

The fall webworm, (Drury) is a major invasive pest in China. Aminopeptidase N (APN) isoforms in lepidopteran larvae midguts are known for their involvement in the mode of action of insecticidal crystal (Cry) proteins from . In the present work, we identified a putative Cry1Ab toxin-binding protein, an APN isoform designated HcAPN3, in the midgut of by ligand blot and mass spectrometry. was highly expressed throughout all larval developmental stages and was abundant in the midgut and hindgut tissues. was down-regulated at 6 h, then was up-regulated significantly at 12 h and 24 h after Cry1Ab toxin treatment. We expressed HcAPN3 in insect cells and detected its interaction with Cry1Ab toxin by ligand blot assays. Furthermore, RNA interference (RNAi) against using oral delivery and injection of double-stranded RNA (dsRNA) resulted in a 61-66% decrease in transcript level. Down-regulating of the expression of HcAPN3 was closely associated with reduced susceptibility of to Cry1Ab. In addition, the HcAPN3E fragment peptide expressed in enhanced Cry1Ab toxicity against larvae. This work represents the first evidence to suggest that an APN in is a putative binding protein involved in Cry1Ab susceptibility.