Shared midgut binding sites for Cry1A.105, Cry1Aa, Cry1Ab, Cry1Ac and Cry1Fa proteins from Bacillus thuringiensis in two important corn pests, Ostrinia nubilalis and Spodoptera frugiperda.

Carmen Sara Hernández-Rodríguez,Patricia Hernández-Martínez,Jeroen Van Rie,Juan Ferré,Baltasar Escriche,Guy Smagghe

doi:10.1371/journal.pone.0068164

Carmen Sara Hernández-Rodríguez, Patricia Hernández-Martínez + Show 4 more

Open Access

https://doi.org/10.1371/journal.pone.0068164

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Journal: PloS one	Publication Date: Jul 5, 2013
Citations: 156	License type: CC BY 4.0

Affiliation: University of Valencia, Bayer (Belgium)

Abstract

First generation of insect-protected transgenic corn (Bt-corn) was based on the expression of Cry1Ab or Cry1Fa proteins. Currently, the trend is the combination of two or more genes expressing proteins that bind to different targets. In addition to broadening the spectrum of action, this strategy helps to delay the evolution of resistance in exposed insect populations. One of such examples is the combination of Cry1A.105 with Cry1Fa and Cry2Ab to control O. nubilalis and S. frugiperda. Cry1A.105 is a chimeric protein with domains I and II and the C-terminal half of the protein from Cry1Ac, and domain III almost identical to Cry1Fa. The aim of the present study was to determine whether the chimeric Cry1A.105 has shared binding sites either with Cry1A proteins, with Cry1Fa, or with both, in O. nubilalis and in S. frugiperda. Brush-border membrane vesicles (BBMV) from last instar larval midguts were used in competition binding assays with 125I-labeled Cry1A.105, Cry1Ab, and Cry1Fa, and unlabeled Cry1A.105, Cry1Aa, Cry1Ab, Cry1Ac, Cry1Fa, Cry2Ab and Cry2Ae. The results showed that Cry1A.105, Cry1Ab, Cry1Ac and Cry1Fa competed with high affinity for the same binding sites in both insect species. However, Cry2Ab and Cry2Ae did not compete for the binding sites of Cry1 proteins. Therefore, according to our results, the development of cross-resistance among Cry1Ab/Ac, Cry1A.105, and Cry1Fa proteins is possible in these two insect species if the alteration of shared binding sites occurs. Conversely, cross-resistance between these proteins and Cry2A proteins is very unlikely in such case.

Highlights

The spraying of insecticidal products on corn plant surfaces is a strategy of limited effectiveness because the larvae from several species tunnel throughout the stem or feed from the roots
The first cultivated Bt-corn expressed a single B. thuringiensis protein, Cry1Ab, which is highly active against the European corn borer, Ostrinia nubilalis
Binding of 125I-labeled Cry1Fa to Brush-border membrane vesicles (BBMV) Competition binding assays using labeled Cry1Fa are shown in Bacillus thuringiensis is a good source of insecticidal proteins

Summary

Introduction

The spraying of insecticidal products on corn plant surfaces is a strategy of limited effectiveness because the larvae from several species tunnel throughout the stem or feed from the roots. Engineered corn plants expressing Cry proteins from Bacillus thuringiensis (Bt-corn) can effectively control stem borers, ear feeders and rootworms, reducing at the same time environmental costs associated with the use of conventional insecticides [1], [2]. The first cultivated Bt-corn expressed a single B. thuringiensis protein, Cry1Ab, which is highly active against the European corn borer, Ostrinia nubilalis (one of the most important lepidopteran pests in northern production areas). This was the only type of Btcorn that was commercially planted until relatively recently and it accounts for most of the area planted worldwide. Other types of Bt-corn that have been developed later on are those designed for the control of rootworms, expressing Cry proteins

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