The crystal δ‐endotoxins of <i>Bacillus thuringiensis</i>: Models for their mechanism of action on the insect gut

Knowles, Barbara H.; Dow, Julian A. T.

doi:10.1002/bies.950150706

Cited by 162 publications

(93 citation statements)

References 42 publications

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“…Among the best alternatives for chemical insecticides are the insecticidal Cry and Cyt proteins produced by Bacillus thuringiensis (2). Shortly after ingestion, these proteins bind to and lyse insect midgut epithelial cells (3). They are highly specific in comparison to chemical insecticides and degrade in the environment days after use.…”

mentioning

confidence: 99%

CytA enables CryIV endotoxins of Bacillus thuringiensis to overcome high levels of CryIV resistance in the mosquito, Culex quinquefasciatus

Wirth

Georghiou

Federici

1997

Proc. Natl. Acad. Sci. U.S.A.

177

149

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Cry proteins produced by Bacillus thuringiensis are selective biodegradable insecticides used increasingly in bacterial insecticides and transgenic plants as alternatives to synthetic chemical insecticides. However, the potential for development of resistance and cross-resistance in target insect populations to Cry proteins used alone or in combination threatens the more widespread use of this novel pest control technology. Here we show that high levels of resistance to CryIV proteins in larvae of the mosquito, Culex quinquefasciatus, can be suppressed or reduced markedly by combining these proteins with sublethal quantities of CytA, a cytolytic endotoxin of B. thuringiensis. Resistance at the LC 95 level of 127-fold for a combination of three CryIV toxins (CryIVA, B, and D), resulting from 60 generations of continuous selection, was completely suppressed by combining sporulated powders of CytA in a 1:3 ratio with sporulated powders of a CryIVA, CryIVB, and CryIVD strain. Combining the CytA strain with a CryIVA and CryIVB strain also completely suppressed mosquito resistance of 217-fold to the latter toxins at the LC 95 level, whereas combination of CytA with CryIVD reduced resistance in a CryIVD-selected mosquito strain from greater than 1,000-fold to less than 8-fold. The CytA͞CryIV model provides a potential molecular genetic strategy for engineering resistance management for Cry proteins directly into bacterial insecticides and transgenic plants.

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mentioning

confidence: 99%

CytA enables CryIV endotoxins of Bacillus thuringiensis to overcome high levels of CryIV resistance in the mosquito, Culex quinquefasciatus

Wirth

Georghiou

Federici

1997

Proc. Natl. Acad. Sci. U.S.A.

177

149

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“…toxin-induced change in cell membrane permeability, but the nature of the toxin lesion is still disputed (Knowles and Dow, 1993). Studies using artificial membranes have demonstrated that some Cry toxin preparations can form channels (Slatin et al, 1990;Schwartz et al, 1993;Grochulski et al, 1995).…”

mentioning

confidence: 99%

Analysis of the Large Aqueous Pores Produced by a Bacillus Turingiensis Protein Insecticide in Manduca Sexta Midgut‐Brush‐Border‐Membrane Vesicles

Carroll

Ellar

1997

European Journal of Biochemistry

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An osmotic swelling assay utilising carboxyfluorescein self-quenching to measure intravesicular volume changes was adapted to investigate permeability changes induced by the Bacillus thuringiensis Cry 1Ac b-endotoxin in Manduca sexta midgut-brush-border-membrane vesicles (BBMV). This assay provides a more quantitative analysis of Cry-toxin-induced BBMV permeability changes, extending our previously published protocol which employed a light-scattering signal to monitor b-endotoxin activity supported by electron microscopy of the BBMV, demonstrated that Cryl Ac altered the membrane permeability for large non-electrolyte solutes. With this approach CrylAc was observed to induce or form pores freely permeant for raffinose (1.14 nm diameter) and using non-electrolytes of increasing size the pores were estimated to have a limiting diameter of approximately 2.4-2.6 nm under alkaline pH conditions.

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“…The larvae of insect orders primarily affected by Bt toxins are Lepidoptera (butterflies and moths), Diptera (mosquitoes) and Coleoptera (larval and adult beetles) [101]. However, Bt toxins are not toxic to people, wildlife, or most beneficial insects [102,103] and therefore the opportunities for biological control are great.…”

Section: The Bacillus Thuringiensis Endotoxinsmentioning

confidence: 99%

Biotechnological Approaches for the Control of Insect Pests in Crop Plants

Stevens¹,

Dunse²,

Fox³

et al. 2012

Pesticides - Advances in Chemical and Botanical Pesticides

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The crystal δ‐endotoxins of Bacillus thuringiensis: Models for their mechanism of action on the insect gut

Cited by 162 publications

References 42 publications

CytA enables CryIV endotoxins of Bacillus thuringiensis to overcome high levels of CryIV resistance in the mosquito, Culex quinquefasciatus

CytA enables CryIV endotoxins of Bacillus thuringiensis to overcome high levels of CryIV resistance in the mosquito, Culex quinquefasciatus

Analysis of the Large Aqueous Pores Produced by a Bacillus Turingiensis Protein Insecticide in Manduca Sexta Midgut‐Brush‐Border‐Membrane Vesicles

Biotechnological Approaches for the Control of Insect Pests in Crop Plants

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