Mode of action of Bacillus thuringiensis toxin CryIIIA: An analysis of toxicity in Leptinotarsa decemlineata (Say) and Diabrotica undecimpunctata howardi Barber

Slaney, Annette C.; Robbins, H L; English, Leigh

doi:10.1016/0965-1748(92)90094-u

Cited by 50 publications

(34 citation statements)

References 23 publications

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“…Whereas Cry3Bb is toxic to SCRW, Cry3Aa has extremely low toxicity to this pest ( Fig. 3A and Table 1) (8,24). The ability of the CR8-10 peptide to enhance Cry3Aa and Cry3Bb toxicity to SCRW was tested using a 1:10 (Cry3-CR8-10) mass ratio.…”

Section: Resultsmentioning

confidence: 99%

Enhancement ofBacillus thuringiensisCry3Aa and Cry3Bb Toxicities to Coleopteran Larvae by a Toxin-Binding Fragment of an Insect Cadherin

Park¹,

Abdullah

Taylor

et al. 2009

Appl Environ Microbiol

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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 ␣-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.

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Section: Resultsmentioning

confidence: 99%

Enhancement ofBacillus thuringiensisCry3Aa and Cry3Bb Toxicities to Coleopteran Larvae by a Toxin-Binding Fragment of an Insect Cadherin

Park¹,

Abdullah

Taylor

et al. 2009

Appl Environ Microbiol

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“…Previous work has reported an effect of Cry toxins on vesicle water permeability with an observed increase in the rate of vesicle shrinkage in the presence of Cry toxin and an imposed salt gradient (English et al, 1991;Slaney et al, 1992). No reference was made to any subsequent swelling of the vesicles which would have been indicative of solute permeability and the ratio of toxidBBMV protein used was either not clearly defined or involved a large excess of toxin when reported receptor-site concentrations are taken into account for the toxin-insect interaction studied (Van Rie et al, 1989;Gould et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

An analysis of Bacillus thuringiensisδ‐endotoxin action on insect‐midgut‐membrane permeability using a light‐scattering assay

Carroll

Ellar

1993

European Journal of Biochemistry

108

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Changes in the membrane permeability of Manduca sexta midgut brush-border-membrane vesicles (BBMV) after addition of Bacillus thuringiensis S-endotoxins were studied using osmotic swelling experiments, volume changes being monitored as the change in 90" light scattering. Typically, control BBMV exhibited limited permeability for sucrose and salts (KCl), while being permeable for urea and glucose. The action of d-endotoxin was examined using proteolytically activated Cry-IA(c) and CryIB toxins. CryIA(c) produced a marked change in the solute permeability of M. sexta BBMV, significant effects being observed at 3.75 pmol/mg BBMV. The permeability change was relatively non-selective with cations, anions and neutral solutes all traversing the membrane to an increased extent in the presence of CryIA(c). In contrast, the CryIB toxin had no effect on BBMV permeability.

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“…Saturable binding to specific receptors has been shown amply with Cry1 proteins (reviewed in reference 37) and more limitedly with the coleopteran-active Cry3A (6,30,34,41) and the dipteran-specific Cry4 and Cry11 class proteins (1,11,31,35). In contrast, an early study of the mode of action of Cry2Aa proposed a unique mode of action for this protein in that binding was nonsaturable (13).…”

Section: Homologous-competition Assays Withmentioning

confidence: 99%

Specific Binding of Bacillus thuringiensis Cry2A Insecticidal Proteins to a Common Site in the Midgut of Helicoverpa Species

Hernández‐Rodríguez

Vliet

Bautsoens

et al. 2008

Appl Environ Microbiol

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For a long time, it has been assumed that the mode of action of Cry2A toxins was unique and different from that of other three-domain Cry toxins due to their apparent nonspecific and unsaturable binding to an unlimited number of receptors. However, based on the homology of the tertiary structure among three-domain Cry toxins, similar modes of action for all of them are expected. To confirm this hypothesis, binding assays were carried out with 125 I-labeled Cry2Ab. Saturation assays showed that Cry2Ab binds in a specific and saturable manner to brush border membrane vesicles (BBMVs) of Helicoverpa armigera. Homologous-competition assays with125 I-Cry2Ab demonstrated that this toxin binds with high affinity to binding sites in H. armigera and Helicoverpa zea midgut. Heterologous-competition assays showed a common binding site for three toxins belonging to the Cry2A family (Cry2Aa, Cry2Ab, and Cry2Ae), which is not shared by Cry1Ac. Estimation of K d (dissociation constant) values revealed that Cry2Ab had around 35-fold less affinity than Cry1Ac for BBMV binding sites in both insect species. Only minor differences were found regarding R t (concentration of binding sites) values. This study questions previous interpretations from other authors performing binding assays with Cry2A toxins and establishes the basis for the mode of action of Cry2A toxins.

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Mode of action of Bacillus thuringiensis toxin CryIIIA: An analysis of toxicity in Leptinotarsa decemlineata (Say) and Diabrotica undecimpunctata howardi Barber

Cited by 50 publications

References 23 publications

Enhancement ofBacillus thuringiensisCry3Aa and Cry3Bb Toxicities to Coleopteran Larvae by a Toxin-Binding Fragment of an Insect Cadherin

Enhancement ofBacillus thuringiensisCry3Aa and Cry3Bb Toxicities to Coleopteran Larvae by a Toxin-Binding Fragment of an Insect Cadherin

An analysis of Bacillus thuringiensisδ‐endotoxin action on insect‐midgut‐membrane permeability using a light‐scattering assay

Specific Binding of Bacillus thuringiensis Cry2A Insecticidal Proteins to a Common Site in the Midgut of Helicoverpa Species

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