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Applied and Environmental Microbiology, February 2007, p. 1199-1207, Vol. 73, No. 4
0099-2240/07/$08.00+0     doi:10.1128/AEM.01834-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Mechanism of Resistance to Bacillus thuringiensis Toxin Cry1Ac in a Greenhouse Population of the Cabbage Looper, Trichoplusia ni{triangledown}

Ping Wang,1* Jian-Zhou Zhao,1 Ana Rodrigo-Simón,2 Wendy Kain,1 Alida F. Janmaat,3 Anthony M. Shelton,1 Juan Ferré,2 and Judith Myers3

Department of Entomology, Cornell University, New York State Agricultural Experiment Station, Geneva, New York 14456,1 Department of Genetics, University of Valencia, Dr. Moliner 50, 46100 Burjassot (Valencia), Spain,2 Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada3

Received 2 August 2006/ Accepted 11 December 2006

The cabbage looper, Trichoplusia ni, is one of only two insect species that have evolved resistance to Bacillus thuringiensis in agricultural situations. The trait of resistance to B. thuringiensis toxin Cry1Ac from a greenhouse-evolved resistant population of T. ni was introgressed into a highly inbred susceptible laboratory strain. The resulting introgression strain, GLEN-Cry1Ac-BCS, and its nearly isogenic susceptible strain were subjected to comparative genetic and biochemical studies to determine the mechanism of resistance. Results showed that midgut proteases, hemolymph melanization activity, and midgut esterase were not altered in the GLEN-Cry1Ac-BCS strain. The pattern of cross-resistance of the GLEN-Cry1Ac-BCS strain to 11 B. thuringiensis Cry toxins showed a correlation of the resistance with the Cry1Ab/Cry1Ac binding site in T. ni. This cross-resistance pattern is different from that found in a previously reported laboratory-selected Cry1Ab-resistant T. ni strain, evidently indicating that the greenhouse-evolved resistance involves a mechanism different from the laboratory-selected resistance. Determination of specific binding of B. thuringiensis toxins Cry1Ab and Cry1Ac to the midgut brush border membranes confirmed the loss of midgut binding to Cry1Ab and Cry1Ac in the resistant larvae. The loss of midgut binding to Cry1Ab/Cry1Ac is inherited as a recessive trait, which is consistent with the recessive inheritance of Cry1Ab/Cry1Ac resistance in this greenhouse-derived T. ni population. Therefore, it is concluded that the mechanism for the greenhouse-evolved Cry1Ac resistance in T. ni is an alteration affecting the binding of Cry1Ab and Cry1Ac to the Cry1Ab/Cry1Ac binding site in the midgut.

* Corresponding author. Mailing address: Department of Entomology, Cornell University, NYSAES, Geneva, NY 14456. Phone: (315) 787-2348. Fax: (315) 787-2326. E-mail: pw15{at}cornell.edu.

{triangledown} Published ahead of print on 22 December 2006.

Applied and Environmental Microbiology, February 2007, p. 1199-1207, Vol. 73, No. 4
0099-2240/07/$08.00+0     doi:10.1128/AEM.01834-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Anilkumar, K. J., Rodrigo-Simon, A., Ferre, J., Pusztai-Carey, M., Sivasupramaniam, S., Moar, W. J. (2008). Production and Characterization of Bacillus thuringiensis Cry1Ac-Resistant Cotton Bollworm Helicoverpa zea (Boddie). Appl. Environ. Microbiol. 74: 462-469 [Abstract] [Full Text]  


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