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Applied and Environmental Microbiology, May 2009, p. 3086-3092, Vol. 75, No. 10
0099-2240/09/$08.00+0     doi:10.1128/AEM.00268-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Enhancement of Bacillus thuringiensis Cry3Aa and Cry3Bb Toxicities to Coleopteran Larvae by a Toxin-Binding Fragment of an Insect Cadherin{triangledown} ,{dagger}

Youngjin Park,1 Mohd Amir F. Abdullah,3 Milton D. Taylor,3 Khalidur Rahman,1 and Michael J. Adang1,2*

Departments of Entomology,1 Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602-2603,2 InsectiGen, Inc., 425 River Road, Athens, Georgia 30602-27713

Received 3 February 2009/ Accepted 19 March 2009

The Cry3Aa and Cry3Bb insecticidal proteins of Bacillus thuringiensis are used in biopesticides and transgenic crops to control larvae of leaf-feeding beetles and rootworms. Cadherins localized in the midgut epithelium are identified as receptors for Cry toxins in lepidopteran and dipteran larvae. Previously, we discovered that a peptide of a toxin-binding cadherin expressed in Escherichia coli functions as a synergist for Cry1A toxicity against lepidopteran larvae and Cry4 toxicity against dipteran larvae. Here we report that the fragment containing the three most C-terminal cadherin repeats (CR) from the cadherin of the western corn rootworm binds toxin and enhances Cry3 toxicity to larvae of naturally susceptible species. The cadherin fragment (CR8 to CR10 [CR8-10]) of western corn rootworm Diabrotica virgifera virgifera was expressed in E. coli as an inclusion body. By an enzyme-linked immunosorbent microplate assay, we demonstrated that the CR8-10 peptide binds {alpha}-chymotrypsin-treated Cry3Aa and Cry3Bb toxins at high affinity (11.8 nM and 1.4 nM, respectively). Coleopteran larvae ingesting CR8-10 inclusions had increased susceptibility to Cry3Aa or Cry3Bb toxin. The Cry3 toxin-enhancing effect of CR8-10 was demonstrated for Colorado potato beetle Leptinotarsa decemlineata, southern corn rootworm Diabrotica undecimpunctata howardi, and western corn rootworm. The extent of Cry3 toxin enhancement, which ranged from 3- to 13-fold, may have practical applications for insect control. Cry3-containing biopesticides that include a cadherin fragment could be more efficacious. And Bt corn (i.e., corn treated with B. thuringiensis to make it resistant to pests) coexpressing Cry3Bb and CR8-10 could increase the functional dose level of the insect toxic activity, reducing the overall resistance risk.

* Corresponding author. Mailing address: Department of Entomology, University of Georgia, Athens, GA 30602-2603. Phone: (706) 542-2436. Fax: (706) 542-2279. E-mail: adang{at}uga.edu

{triangledown} Published ahead of print on 27 March 2009.

{dagger} Supplemental material for this article may be found at http://aem.asm.org/.

Applied and Environmental Microbiology, May 2009, p. 3086-3092, Vol. 75, No. 10
0099-2240/09/$08.00+0     doi:10.1128/AEM.00268-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Park, Y., Hua, G., Abdullah, M. A. F., Rahman, K., Adang, M. J. (2009). Cadherin Fragments from Anopheles gambiae Synergize Bacillus thuringiensis Cry4Ba's Toxicity against Aedes aegypti Larvae. Appl. Environ. Microbiol. 75: 7280-7282 [Abstract] [Full Text]  
  • Fabrick, J., Oppert, C., Lorenzen, M. D., Morris, K., Oppert, B., Jurat-Fuentes, J. L. (2009). A Novel Tenebrio molitor Cadherin Is a Functional Receptor for Bacillus thuringiensis Cry3Aa Toxin. J. Biol. Chem. 284: 18401-18410 [Abstract] [Full Text]  


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