The Mode of Action of Bacillus Thuringiensis Endotoxins

Gill, Sarjeet S.; Cowles, Elizabeth A.; Pietrantonio, Patricia V.

doi:10.1146/annurev.en.37.010192.003151

Cited by 675 publications

(235 citation statements)

References 46 publications

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“…A survey of the EMBL and GenBank databases reveals that over 90 ICP genes have now been cloned and sequenced. The reader is referred to several recent reviews dealing with the molecular aspects, genetic diversity, and mode of action of the B. thuringiensis ICPs (Aronson, 1993;Feitelson et aL, 1992;Gill et aL, 1992).…”

Section: Introductionmentioning

confidence: 99%

Regulation of insecticidal crystal protein production in Bacillus thuringiensis

Baum¹,

Malvar

1995

Molecular Microbiology

147

116

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SummaryThe production of insecticidal crystal proteins (ICPs) in Bacillus thuringiensis normally coincides with sporulation, resulting in the appearance of parasporal crystalline inclusions within the mother cell. In most instances, the temporal and spatial regulation of ICP gene expression is determined at the transcriptional level by mother-cell-specific sigma factors that share homology with cr E and eK from Bacillus subtilis. The crylll ICP genes are a notable exception; these genes are transcribed from eA-like promoters during vegetative growth, are induced or derepressed at the onset of stationary phase, and are overexpressed in sporulation mutants of B. thuringiensis blocked in the phosphorylation of Spo0A, a key regulator of sporulation initiation. Transcription alone, however, cannot account for the impressive ability of this bacterium to accumulate insecticidal proteins. A variety of post-transcriptional and post-translational mechanisms also contribute to the efficient production of ICPs in B. thuringiensis, thus making this bacterium a cost-effective biological control agent.

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Section: Introductionmentioning

confidence: 99%

Regulation of insecticidal crystal protein production in Bacillus thuringiensis

Baum¹,

Malvar

1995

Molecular Microbiology

147

116

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“…B acillus thuringiensis is an opportunistic insect pathogen that was discovered almost a century ago (1)(2)(3)(4)(5)(6)(7). The salient feature of this species is accumulation of crystalline parasporal inclusions during sporulation.…”

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confidence: 99%

“…In addition, rapid turnover of gut epithelial cells permits larvae to recover from toxin-induced feeding inhibition (8)(9)(10). The septicemia model is challenged by the observation that the toxin causes mortality when it is separated from the bacterial cells, which has been accomplished with purified toxin and transgenic plants that produce the toxin (1)(2)(3)(4)6).…”

mentioning

confidence: 99%

Midgut bacteria required for Bacillus thuringiensis insecticidal activity

Broderick

Raffa²,

Handelsman³

2006

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

393

334

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Bacillus thuringiensis is the most widely applied biological insecticide and is used to manage insects that affect forestry and agriculture and transmit human and animal pathogens. This ubiquitous spore-forming bacterium kills insect larvae largely through the action of insecticidal crystal proteins and is commonly deployed as a direct bacterial spray. Moreover, plants engineered with the cry genes encoding the B. thuringiensis crystal proteins are the most widely cultivated transgenic crops. For decades, the mechanism of insect killing has been assumed to be toxin-mediated lysis of the gut epithelial cells, which leads to starvation, or B. thuringiensis septicemia. Here, we report that B. thuringiensis does not kill larvae of the gypsy moth in the absence of indigenous midgut bacteria. Elimination of the gut microbial community by oral administration of antibiotics abolished B. thuringiensis insecticidal activity, and reestablishment of an Enterobacter sp. that normally resides in the midgut microbial community restored B. thuringiensis-mediated killing. Escherichia coli engineered to produce the B. thuringiensis insecticidal toxin killed gypsy moth larvae irrespective of the presence of other bacteria in the midgut. However, when the engineered E. coli was heat-killed and then fed to the larvae, the larvae did not die in the absence of the indigenous midgut bacteria. E. coli and the Enterobacter sp. achieved high populations in hemolymph, in contrast to B. thuringiensis, which appeared to die in hemolymph. Our results demonstrate that B. thuringiensis-induced mortality depends on enteric bacteria.insect-microbe interactions ͉ microbe-microbe interactions ͉ synergy ͉ Lepidoptera ͉ pore-forming toxin

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“…These toxins kill insects by binding to and creating pores in midgut membranes (2). Each of the many strains of Bt produces a characteristic set of crystal proteins (1).…”

mentioning

confidence: 99%

Global variation in the genetic and biochemical basis of diamondback moth resistance to Bacillus thuringiensis

Tabashnik

Liu

Malvar

et al. 1997

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

202

155

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Insecticidal proteins from the soil bacterium Bacillus thuringiensis (Bt) are becoming a cornerstone of ecologically sound pest management. However, if pests quickly adapt, the benefits of environmentally benign Bt toxins in sprays and genetically engineered crops will be short-lived. The diamondback moth (Plutella xylostella) is the first insect to evolve resistance to Bt in open-field populations. Here we report that populations from Hawaii and Pennsylvania share a genetic locus at which a recessive mutation associated with reduced toxin binding confers extremely high resistance to four Bt toxins. In contrast, resistance in a population from the Philippines shows multilocus control, a narrower spectrum, and for some Bt toxins, inheritance that is not recessive and not associated with reduced binding. The observed variation in the genetic and biochemical basis of resistance to Bt, which is unlike patterns documented for some synthetic insecticides, profoundly affects the choice of strategies for combating resistance.

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The Mode of Action of Bacillus Thuringiensis Endotoxins

Cited by 675 publications

References 46 publications

Regulation of insecticidal crystal protein production in Bacillus thuringiensis

Regulation of insecticidal crystal protein production in Bacillus thuringiensis

Midgut bacteria required for Bacillus thuringiensis insecticidal activity

Global variation in the genetic and biochemical basis of diamondback moth resistance to Bacillus thuringiensis

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