Aminopeptidase N1 is involved in Bacillus thuringiensis Cry1Ac toxicity in the beet armyworm, Spodoptera exigua

Lin Qiu,Boyao Zhang,Lizhen Chen,Chaoliang Lei,Weihua Ma,Songhe Cui,Lang Liu,Xiaoping Wang

doi:10.1038/srep45007

Lin Qiu, Boyao Zhang + Show 6 more

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https://doi.org/10.1038/srep45007

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Abstract

Understanding how insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) interact with their hosts is crucial to fully explain the molecular bases of Bt specificity and insecticidal activity. Previous studies support ATP binding cassette transporters (ABCC2/3) and one cadherin-like protein are Cry1Ac functional receptors in the beet armyworm (Spodoptera exigua). In this study, a combined one-dimensional gel electrophoresis and immunoblotting approach identified aminopeptidase N (APNs) as putative Cry1Ac binding proteins in the midgut brush border membrane of S. exigua larvae. Functional analyses by gene silencing of six different S. exigua APN genes (SeAPN1, SeAPN2, SeAPN3, SeAPN4, SeAPN5 and SeAPN6) showed that only suppression of SeAPN1 resulted in decreased larval susceptibility to Cry1Ac toxin. These results support that SeAPN1 plays important functional role in Cry1Ac toxicity in S. exigua.

Highlights

Understanding how insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) interact with their hosts is crucial to fully explain the molecular bases of Bt specificity and insecticidal activity
We focused our analyses on testing the functional Cry1Ac-receptor role of S. exigua aminopeptidase N (APN) (SeAPNs)
Expression of a Manduca sexta APN gene in transgenic Drosophila resulted in susceptibility to Cry1Ac toxin[22]

Summary

Introduction

Understanding how insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) interact with their hosts is crucial to fully explain the molecular bases of Bt specificity and insecticidal activity. A combined one-dimensional gel electrophoresis and immunoblotting approach identified aminopeptidase N (APNs) as putative Cry1Ac binding proteins in the midgut brush border membrane of S. exigua larvae. Functional analyses by gene silencing of six different S. exigua APN genes (SeAPN1, SeAPN2, SeAPN3, SeAPN4, SeAPN5 and SeAPN6) showed that only suppression of SeAPN1 resulted in decreased larval susceptibility to Cry1Ac toxin. The crystal (Cry) proteins from the bacterium Bacillus thuringiensis (Bt) are a diverse group of insecticidal proteins employed for the control of numerous pest species from different insect orders[1]. These Cry proteins are active ingredients in Bt sprayable formulations, and cry genes have been transformed into transgenic plants for resistance to insect attack. Using functional assays by RNA interference (RNAi) to individually silence expression of known S. exigua APN genes, we document the identification of APN protein relevant to Cry1Ac intoxication in that insect pest

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