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ARS Home » Pacific West Area » Maricopa, Arizona » U.S. Arid Land Agricultural Research Center » Pest Management and Biocontrol Research » Research » Publications at this Location » Publication #264276

Title: Insertion of an intact CR1 retrotranspon in a cadherin gene linked with BT resistance in the pink bollworm, Pectinophora gossypiella

item Fabrick, Jeffrey
item Mathew, Lolita
item TABASHNIK, BRUCE - University Of Arizona
item LI, XIANCHUN - University Of Arizona

Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/6/2011
Publication Date: 10/1/2011
Citation: Fabrick, J.A., Mathew, L.G., Tabashnik, B.E., Li, X. (2011). Insertion of an intact CR1 retrotranspon in a cadherin gene linked with BT resistance in the pink bollworm, Pectinophora gossypiella. Insect Molecular Biology. 20(5):651-665

Interpretive Summary: Much of the cotton currently grown in the U.S. has been engineered to produce insecticidal proteins from the bacterium, Bacillus thuringiensis or Bt. These Bt proteins target major agricultural pests, including the pink bollworm, Pectinophora gossypiella. The pink bollworm is a major cotton pest shown to become resistant to Bt proteins in the laboratory and to Bt cotton in the field in India. In laboratory selected pink bollworm, three changes or mutations in a gene called cadherin are linked with resistance to Bt. Here we show that one cadherin mutation entails recent insertion an active mobile DNA element, designated CR1-1_Pg. Characterization of CR1-1_Pg revealed a number of unique properties, most importantly that it is intact and remains capable of transposition. Furthermore, other insects resistant to Bt have their cadherin gene disrupted by transposable elements, suggesting that this gene is a common target for insertion by mobile DNA. These results reveal new information regarding the underlying genetic mechanism of Bt resistance and thus provides new opportunities for resistance monitoring and the design of pest management strategies that do not favor the evolution of field-evolved resistance to Bt crops.

Technical Abstract: Three mutations in the Pectinophora gossypiella cadherin gene PgCad1 are linked to resistance to Bacillus thuringiensis (Bt) toxin Cry1Ac. Here we show that the r3 mutation entails recent insertion into PgCad1 of an active chicken repeat (CR1) retrotransposon, designated CR1-1_Pg. Unlike most other CR1 elements, CR1-1_Pg is intact, transcribed by a flanking promoter, contains target site duplications, and has a relatively low number of copies. Examination of transcripts from the PgCad1 locus reveals CR1-1_Pg disrupts both the cadherin protein and a long non-coding RNA of unknown function. These findings bring the current total number of cadherin alleles disrupted by transposable elements and linked with Bt resistance to eight out of twelve in three lepidopteran species, indicating that the cadherin locus is a common target for disruption by transposable elements.