Analysis of Cry1Ah Toxin-Binding Reliability to Midgut Membrane Proteins of the Asian Corn Borer.

Sivaprasath Prabu,Kanglai He,Muhammad Zeeshan Shabbir,Zhenying Wang

doi:10.3390/toxins12060418

Sivaprasath Prabu, Kanglai He + Show 2 more

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https://doi.org/10.3390/toxins12060418

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Abstract

Evolution of insect resistance to Bt toxins challenges the use of Cry toxins to control agricultural pests. In lepidopterans, Cry toxin affinity towards multiple midgut epithelial receptors has become a matter of dispute. Cry1Ah toxin-binding proteins were identified in the larval midgut of susceptible (ACB-BtS) and resistant (ACB-AhR) strains of the Asian corn borer (ACB). A pull-down assay was performed using biotinylated Cry1Ah toxin, and the binding proteins were identified by employing liquid chromatography–tandem mass spectrometry (LC-MS/MS). This study aimed to find the binding consistency of the midgut epithelial protein to the Cry1Ah toxin. The binding proteins from different fractions of SDS-PAGE showed a different pattern. We observed an isoform of prophenoloxidase PPO1b (UniProt Acc No. A0A1Q1MKI0), which was found only in the ACB-AhR fractions. Prophenoloxidase (proPO) is an extraordinary defense molecule activated in insect species during pathogen invasion and the wound healing process. Importantly, this prophenoloxidase might have direct/indirect interaction with the Cry1Ah toxin. Our data also suggest that factors like techniques, enrichment of binding proteins in the sample and the reversible and irreversible nature of the brush border membrane vesicles (BBMVs) to Cry toxins could cause the inconsistency in the protein–protein interactions. Moreover, inside the larva midgut, the influence of the Cry toxins under physiological conditions might be different from the laboratory procedures.

Highlights

The Bacillus thuringiensis (Bt) insecticidal crystal (Cry) proteins are a diverse family of proteins with over 780 identified members [1]
Enrichment of brush border membrane vesicles (BBMVs) proteins was indicated by the high ratios of APN and alkaline phosphatase (ALP) activities in the BBMV sample extracted from the midgut homogenate
The biotinylated Cry1Ah interacted with the BBMV proteins extracted from the Asian corn borer (ACB)-BtS and ACB-AhR strains and were analyzed using 12% Gel (Figure 1)

Summary

Introduction

The Bacillus thuringiensis (Bt) insecticidal crystal (Cry) proteins are a diverse family of proteins with over 780 identified members [1]. The wide variety of these toxins, their effectiveness and relatively inexpensive processing have made Bt the world’s most commonly used biopesticide. These Cry proteins are used as sprays or as a Cry gene expressing transgenic crops, and are used mainly in the fight against lepidopteran and other agricultural crop pests [2]. The extensive use of transgenic crops raises the selection pressure to evolve insect resistance to the Bt proteins, decreasing the effectiveness of the Bt Cry proteins [3,4,5].

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