The Insecticidal Crystal Proteins of<i>Bacillus thuringiensis</i>: Past, Present and Future Uses

Koziel, Michael G.; Carozzi, Nadine B.; Currier, Thomas C.; Warren, Gregory W.; Evola, Stephen V.

doi:10.1080/02648725.1993.10647901

Cited by 64 publications

(27 citation statements)

References 123 publications

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“…In studies of 15 species of insects, only P. xylostella populations exhibited major differences in susceptibility that can be attributed to previous exposure to B. thuringiensis in the field (44). However, it is sometimes difficult to distinguish natural variation among susceptible populations from low to moderate resistance (12,24). The present study did not address resistance per se because the relationship between the history of exposure and susceptibility was not examined.…”

Section: Discussionmentioning

confidence: 99%

Use of Bacillus thuringiensis Toxins for Control of the Cotton Pest Earias insulana (Boisd.) (Lepidoptera: Noctuidae)

Ibargutxi

Estela

Ferré

et al. 2006

Appl Environ Microbiol

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Thirteen of the most common lepidopteran-specific Cry proteins of Bacillus thuringiensis have been tested for their efficacy against newly hatched larvae of two populations of the spiny bollworm, Earias insulana. At a concentration of 100 g of toxin per milliliter of artificial diet, six Cry toxins (Cry1Ca, Cry1Ea, Cry1Fa, Cry1Ja, Cry2Aa, and Cry2Ab) were not toxic at all. Cry1Aa, Cry1Ja, and Cry2Aa did not cause mortality but caused significant inhibition of growth. The other Cry toxins (Cry1Ab, Cry1Ac, Cry1Ba, Cry1Da, Cry1Ia, and Cry9Ca) were toxic to E. insulana larvae. The 50% lethal concentration values of these toxins ranged from 0.39 to 21.13 g/ml (for Cry9Ca and Cry1Ia, respectively) for an E. insulana laboratory colony originating from Egypt and from 0.20 to 4.25 g/ml (for Cry9Ca and Cry1Da, respectively) for a laboratory colony originating from Spain. The relative potencies of the toxins in the population from Egypt were highest for Cry9Ca and Cry1Ab, and they were both significantly more toxic than Cry1Ac and Cry1Ba, followed by Cry1Da and finally Cry1Ia. In the population from Spain, Cry9Ca was the most toxic, followed in decreasing order by Cry1Ac and Cry1Ba, and the least toxic was Cry1Da. Binding experiments were performed to test whether the toxic Cry proteins shared binding sites in this insect.125 I-labeled Cry1Ac and Cry1Ab and biotinylated Cry1Ba, Cry1Ia, and Cry9Ca showed specific binding to the brush border membrane vesicles from E. insulana. Competition binding experiments among these toxins showed that only Cry1Ab and Cry1Ac competed for the same binding sites, indicating a high possibility that this insect may develop cross-resistance to Cry1Ab upon exposure to Cry1Ac transgenic cotton but not to the other toxins tested.

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Section: Discussionmentioning

confidence: 99%

Use of Bacillus thuringiensis Toxins for Control of the Cotton Pest Earias insulana (Boisd.) (Lepidoptera: Noctuidae)

Ibargutxi

Estela

Ferré

et al. 2006

Appl Environ Microbiol

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“…The Vip3A insecticidal proteins reported here provide 100% mortality when added at 62 ng of diet per ml. This amount of protein is at least 260-fold lower than the amounts of CrylA proteins needed to achieve just 50% mortality, and it is similar to the levels of a-endotoxins used for insects susceptible to 8-endotoxins (17). a-Endotoxins are believed to form lytic pores in the insect gut membranes (18).…”

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confidence: 99%

Vip3A, a novel Bacillus thuringiensis vegetative insecticidal protein with a wide spectrum of activities against lepidopteran insects.

Estruch

Warren

Mullins

et al. 1996

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

599

521

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A novel vegetative insecticidal gene, vip3A(a), whose gene product shows activity against lepidopteran insect larvae including black cutworm (Agrotis ipsilon), fall armyworm (Spodoptera frugiperda), beet armyworm (Spodoptera exigua), tobacco budworm (Heliothis virescens), and corn earworm (Helicoverpa zea) has been isolated from BaciUlus thuringiensis strain AB88. VIP3-insecticidal gene homologues have been detected in "15% of Bacillus strains analyzed. The isolation and characterization of new insecticidal activities is the basis of many pest control programs. Bacillus thuringiensis, a gram-positive soil bacterium, is well known for its ability to produce crystalline inclusions during sporulation which contain insecticidal proteins called S-endotoxins. These inclusions are solubilized in insect midguts, releasing the 6-endotoxins that, upon proteolytic activation, exhibit a highly specific insecticidal activity (1). In the past decades, many B. thuringiensis strains with different insect host spectra have been identified and their $-endotoxins used in formulations for biopesticides (2). Recently, the cloning of $-endotoxin genes (3) and their expression in transgenic plants (4) has provided an alternative strategy for crop protection against insect damage.Although B. thuringiensis 8-endotoxins are effective insecticidal proteins, there are several agronomically important insects that are less sensitive to their action (5). The lepidopteran black cutworm (BCW, Agrotis ipsilon) is an example. BCW is a worldwide pest that attacks more than 50 crops, including cereal grains (6). This pest is difficult to control because by the time the infestations are apparent, the susceptible stages (i.e., larvae) are past and damage may already be serious and irreversible.Extensive screening programs are being carried out by various groups to search for B. thuringiensis strains with new insecticidal spectra. These evaluations have focused mainly on the identification of new 6-endotoxins that are expressed during sporulation (7). Our experimental approach focused on bacterial stages before sporulation, and has led to the identification of non-S-endotoxins with insecticidal activities. We describe here the cloning and characterization of vip3A (a) (pH 7.5) and dialyzed overnight at 4°C. The dialysate was titrated to pH 4.5 using 20 mM sodium citrate (pH 2.5). After 30 min incubation at room temperature, the sample was centrifuged at 3000 x g for 10 min. The resulting protein pellet was redissolved in 20 mM BisTris-Propane (pH 9.0) and fractionated on a Poros HQ/N anion exchange column (PerSeptive Biosystems, Framingham, MA) using a linear gradient from 0 to 500 mM NaCl in 20 mM Bis-Tris-Propane (pH 9.0) at a flow rate of 4 ml/min. The insecticidal protein eluted at 250 mM NaCl.Peptide Analysis and Oligonucleotide Synthesis. Fractions with insecticidal activity were fractionated in SDS/8-16% polyacrylamide gradient gels and transferred to poly(vinylidene difluoride) membranes (8). The most abundant protein band (molecular...

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“…B. thuringiensis serovar kurstaki (Btk) is the most commonly used strain in commercial sprayable formulations for lepidopteran pest control. Btk contains both Cry1A and Cry2A toxins (17,18), so Btk formulations are virtually a bioinsecticide with pyramided Bt Cry1A and Cry2A toxins. Therefore, Btk-resistant insect populations may have developed resistance to multiple Bt toxins and offer opportunities to study resistance of insect populations to multiple Bt toxins selected in agriculture.…”

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confidence: 99%

Resistance of Trichoplusia ni Populations Selected by Bacillus thuringiensis Sprays to Cotton Plants Expressing Pyramided Bacillus thuringiensis Toxins Cry1Ac and Cry2Ab

Kain

Song

Janmaat

et al. 2015

Appl Environ Microbiol

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bTwo populations of Trichoplusia ni that had developed resistance to Bacillus thuringiensis sprays (Bt sprays) in commercial greenhouse vegetable production were tested for resistance to Bt cotton (BollGard II) plants expressing pyramided Cry1Ac and Cry2Ab. The T. ni colonies resistant to Bacillus thuringiensis serovar kurstaki formulations were not only resistant to the Bt toxin Cry1Ac, as previously reported, but also had a high frequency of Cry2Ab-resistant alleles, exhibiting ca. 20% survival on BollGard II foliage. BollGard II-resistant T. ni strains were established by selection with BollGard II foliage to further remove Cry2Ab-sensitive alleles in the T. ni populations. The BollGard II-resistant strains showed incomplete resistance to BollGard II, with adjusted survival values of 0.50 to 0.78 after 7 days. The resistance to the dual-toxin cotton plants was conferred by two genetically independent resistance mechanisms: one to Cry1Ac and one to Cry2Ab. The 50% lethal concentration of Cry2Ab for the resistant strain was at least 1,467-fold that for the susceptible T. ni strain. The resistance to Cry2Ab in resistant T. ni was an autosomally inherited, incompletely recessive monogenic trait. Results from this study indicate that insect populations under selection by Bt sprays in agriculture can be resistant to multiple Bt toxins and may potentially confer resistance to multitoxin Bt crops. Evolution of pesticide resistance in insect populations is a continuing threat to the efficacy of both synthetic and biological insecticides. Resistance of insects to the biological insecticide Bacillus thuringiensis (Bt), a naturally occurring soil bacterium, was first reported in the 1980s for a pest of stored grains, Plodia interpunctella (1). Resistance to Bt in Plutella xylostella and Trichoplusia ni has been identified following frequent applications of sprayable Bt formulations in agricultural situations (2-4). Since the mid-1990s, crops genetically engineered to contain insecticidal toxins from Bt have increasingly been adopted worldwide (5). With the wide adoption of Bt crops, insect resistance is a serious threat to their continuing success. Field populations of several major pest species have been reported to have developed resistance after Bt crop adoption, leading to increased crop damage (6, 7). More insect species have been reported to have increased frequencies of resistant alleles in field populations after the adoption of Bt crops (8-11).Selective application of pesticides with different modes of action has been a principal strategy for insecticide resistance management. Similarly, Bt gene pyramiding, i.e., simultaneous expression of multiple toxins that have different binding sites in the target insects, is an effective strategy to delay the development of resistance to Bt crops. This has been promoted for Bt crops currently deployed in the United States and some other regions of the world (7, 12). Bt toxins Cry1Ac and Cry2Ab do not share the same binding sites in target Lepidoptera insects (13,14) and ha...

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The Insecticidal Crystal Proteins ofBacillus thuringiensis: Past, Present and Future Uses

Abstract: Future Uses MICI-IAEL Cj. K()ZIEL~NADINE B. (~i\I~()ZZL~rl"I()rvlAS c(~l JRllIER. (JI{EG()r~Y W. WAI

Cited by 64 publications

References 123 publications

Use of Bacillus thuringiensis Toxins for Control of the Cotton Pest Earias insulana (Boisd.) (Lepidoptera: Noctuidae)

Use of Bacillus thuringiensis Toxins for Control of the Cotton Pest Earias insulana (Boisd.) (Lepidoptera: Noctuidae)

Vip3A, a novel Bacillus thuringiensis vegetative insecticidal protein with a wide spectrum of activities against lepidopteran insects.

Resistance of Trichoplusia ni Populations Selected by Bacillus thuringiensis Sprays to Cotton Plants Expressing Pyramided Bacillus thuringiensis Toxins Cry1Ac and Cry2Ab

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