Affiliation:
1. Departament de Genètica, Facultat CC. Biològiques, Universitat de València, València, Spain
Abstract
ABSTRACT
In 1996, Bt-cotton (cotton expressing a
Bacillus thuringiensis
toxin gene) expressing the Cry1Ac protein was commercially introduced to control cotton pests. A threat to this first generation of transgenic cotton is the evolution of resistance by the insects. Second-generation Bt-cotton has been developed with either new
B. thuringiensis
genes or with a combination of
cry
genes. However, one requirement for the “stacked” gene strategy to work is that the stacked toxins bind to different binding sites. In the present study, the binding of
125
I-labeled Cry1Ab protein (
125
I-Cry1Ab) and
125
I-Cry1Ac to brush border membrane vesicles (BBMV) of
Helicoverpa armigera
was analyzed in competition experiments with 11 nonlabeled Cry proteins. The results indicate that Cry1Aa, Cry1Ab, and Cry1Ac competed for common binding sites. No other Cry proteins tested competed for either
125
I-Cry1Ab or
125
I-Cry1Ac binding, except Cry1Ja, which competed only at the highest concentrations used. Furthermore, BBMV from four
H. armigera
populations were also tested with
125
I-Cry1Ac and Cry1Ab to check the influence of the insect population on the binding results. Finally, the inhibitory effect of selected sugars and lectins was also determined.
125
I-Cry1Ac binding was strongly inhibited by
N
-acetylgalactosamine, sialic acid, and concanavalin A and moderately inhibited by soybean agglutinin. In contrast,
125
I-Cry1Ab binding was only significantly inhibited by concanavalin A. These results show that Cry1Ac and Cry1Ab use different epitopes for binding to BBMV.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
90 articles.
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