Shared Midgut Binding Sites for Bt Proteins in Two Important Corn Pests

Bt insecticidal proteins come in various forms to control target insect pests, among which are European corn borer (Ostrinia. nubilalis) and fall armyworm (Spodoptera frugiperda). With the increasing popularity and usefulness of combining two or more genes to broaden the spectrum of action, scientists at the University of Valencia, Spain and Bayer Crop Science in Ghent, Belgium, headed by Carmen Sara Hernandez-Rodriguez studied extensively the binding sites of the Bt proteins.

A protein competition binding assay was conducted with ¹²⁵Iodine-labeled Cry1A.105, Cry1Ab, and Cry1Fa, and unlabeled Cry1A.105, Cry1Aa, Cry1Ab, Cry1Ac, Cry1Fa, Cry2Ab and Cry2Ae in the brush border membrane vesicles from the last instar larval midguts. Results showed that Cry1A.105, Cry1Ab, Cry1Ac and Cry1Fa proteins competed with high affinity for the same binding sites in both insect pests, but not the Cry2Ab and Cry2Ae proteins.

This indicate that the development of cross-resistance among Cry1Ab/Ac, Cry1A.105, and Cry1Fa proteins is possible in these two insect species if there will be alteration of shared binding sites. Conversely, cross-resistance between these proteins and Cry2A proteins is thus unlikely to occur. These findings also indicate that Cry1A.105 can be an alternative to Cry1Ab/Ac for the control of O. nubilalis, but appears inferior to Cry1Fa for the control of S. frugiperda. It also open possibilities to design effective pyramiding of Bt crops.

See the original research at: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0068164