scholarly journals Evaluating Cross-resistance Between Vip and Cry Toxins of Bacillus thuringiensis

2019 ◽  
Vol 113 (2) ◽  
pp. 553-561 ◽  
Author(s):  
Bruce E Tabashnik ◽  
Yves Carrière
Keyword(s):  
Bacillus Thuringiensis ◽  
Genetically Engineered ◽  
Cross Resistance ◽  
Published Data ◽  
Data Sets ◽  
Cry Proteins ◽  
Cry Toxins ◽  
Bt Crops ◽  
Resistant Strains ◽  
Bacterium Bacillus

Abstract Crops genetically engineered to produce insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have revolutionized control of some major pests. Some recently introduced Bt crops make Vip3Aa, a vegetative insecticidal protein (Vip), which reportedly does not share binding sites or structural homology with the crystalline (Cry) proteins of Bt used widely in transgenic crops for more than two decades. Field-evolved resistance to Bt crops with practical consequences for pest control includes 21 cases that collectively reduce the efficacy of nine Cry proteins, but such practical resistance has not been reported yet for any Vip. Here, we review previously published data to evaluate cross-resistance between Vip and Cry toxins. We analyzed 31 cases based on 48 observations, with each case based on one to five observations assessing cross-resistance from pairwise comparisons between 21 resistant strains and 13 related susceptible strains of eight species of lepidopteran pests. Confirming results from previous analyses of smaller data sets, we found weak, statistically significant cross-resistance between Vip3 and Cry1 toxins, with a mean of 1.5-fold cross-resistance in 21 cases (range: 0.30–4.6-fold). Conversely, we did not detect significant positive cross-resistance between Vip3 toxins and Cry2Ab. Distinguishing between weak, significant cross-resistance, and no cross-resistance may be useful for better understanding mechanisms of resistance and effectively managing pest resistance to Bt crops.

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

2006 ◽  
Vol 72 (1) ◽  
pp. 437-442 ◽  
Author(s):  
María A. Ibargutxi ◽  
Anna Estela ◽  
Juan Ferré ◽  
Primitivo Caballero
Keyword(s):  
Bacillus Thuringiensis ◽  
Binding Sites ◽  
Specific Binding ◽  
Significant Inhibition ◽  
The Other ◽  
Cross Resistance ◽  
Earias Insulana ◽  
Cry Proteins ◽  
Cry Toxins ◽  
Laboratory Colony

ABSTRACT 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 μg 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 μg/ml (for Cry9Ca and Cry1Ia, respectively) for an E. insulana laboratory colony originating from Egypt and from 0.20 to 4.25 μg/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. 125I-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.

scholarly journals Control of Resistant Pink Bollworm (Pectinophora gossypiella) by Transgenic Cotton That Produces Bacillus thuringiensis Toxin Cry2Ab

2002 ◽  
Vol 68 (8) ◽  
pp. 3790-3794 ◽  
Author(s):  
Bruce E. Tabashnik ◽  
Timothy J. Dennehy ◽  
Maria A. Sims ◽  
Karen Larkin ◽  
Graham P. Head ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
First Generation ◽  
Second Generation ◽  
Transgenic Cotton ◽  
Larval Survival ◽  
Genetically Engineered ◽  
Pink Bollworm ◽  
Pectinophora Gossypiella ◽  
Cross Resistance ◽  
Average Survival

ABSTRACT Crops genetically engineered to produce Bacillus thuringiensis toxins for insect control can reduce use of conventional insecticides, but insect resistance could limit the success of this technology. The first generation of transgenic cotton with B. thuringiensis produces a single toxin, Cry1Ac, that is highly effective against susceptible larvae of pink bollworm (Pectinophora gossypiella), a major cotton pest. To counter potential problems with resistance, second-generation transgenic cotton that produces B. thuringiensis toxin Cry2Ab alone or in combination with Cry1Ac has been developed. In greenhouse bioassays, a pink bollworm strain selected in the laboratory for resistance to Cry1Ac survived equally well on transgenic cotton with Cry1Ac and on cotton without Cry1Ac. In contrast, Cry1Ac-resistant pink bollworm had little or no survival on second-generation transgenic cotton with Cry2Ab alone or with Cry1Ac plus Cry2Ab. Artificial diet bioassays showed that resistance to Cry1Ac did not confer strong cross-resistance to Cry2Aa. Strains with >90% larval survival on diet with 10 μg of Cry1Ac per ml showed 0% survival on diet with 3.2 or 10 μg of Cry2Aa per ml. However, the average survival of larvae fed a diet with 1 μg of Cry2Aa per ml was higher for Cry1Ac-resistant strains (2 to 10%) than for susceptible strains (0%). If plants with Cry1Ac plus Cry2Ab are deployed while genes that confer resistance to each of these toxins are rare, and if the inheritance of resistance to both toxins is recessive, the efficacy of transgenic cotton might be greatly extended.

scholarly journals Extent of Variation of the Bacillus thuringiensis Toxin Reservoir: the Case of the Geranium Bronze, Cacyreus marshalli Butler (Lepidoptera: Lycaenidae)

2002 ◽  
Vol 68 (8) ◽  
pp. 4090-4094 ◽  
Author(s):  
Salvador Herrero ◽  
Marisé Borja ◽  
Juan Ferré
Keyword(s):  
Bacillus Thuringiensis ◽  
Binding Site ◽  
Management Strategies ◽  
Resistance Management ◽  
Cross Resistance ◽  
Binding Studies ◽  
Cry Proteins ◽  
Combined Use ◽  
The Common

ABSTRACT Despite the fact that around 200 cry genes from Bacillus thuringiensis have already been cloned, only a few Cry proteins are toxic towards a given pest. A crucial step in the mode of action of Cry proteins is binding to specific sites in the midgut of susceptible insects. Binding studies in insects that have developed cross-resistance discourage the combined use of Cry proteins sharing the same binding site. If resistance management strategies are to be implemented, the arsenal of Cry proteins suitable to control a given pest may be not so vast as it might seem at first. The present study evaluates the potential of B. thuringiensis for the control of a new pest, the geranium bronze (Cacyreus marshalli Butler), a butterfly that is threatening the popularity of geraniums in Spain. Eleven of the most common Cry proteins from the three lepidopteran-active Cry families (Cry1, Cry2, and Cry9) were tested against the geranium bronze for their toxicity and binding site relationships. Using 125I-labeled Cry1A proteins we found that, of the seven most active Cry proteins, six competed for binding to the same site. For the long-term control of the geranium bronze with B. thuringiensis-based insecticides it would be advisable to combine any of the Cry proteins sharing the binding site (preferably Cry1Ab, since it is the most toxic) with those not competing for the same site. Cry1Ba would be the best choice of these proteins, since it is significantly more toxic than the others not binding to the common site.

scholarly journals Bacillus thuringiensis Vip3Aa Toxin Resistance in Heliothis virescens (Lepidoptera: Noctuidae)

2017 ◽  
Vol 83 (9) ◽  
Author(s):  
Brian R. Pickett ◽  
Asim Gulzar ◽  
Juan Ferré ◽  
Denis J. Wright
Keyword(s):  
Bacillus Thuringiensis ◽  
Heliothis Virescens ◽  
Insect Pests ◽  
Management Strategies ◽  
Resistance Management ◽  
Cross Resistance ◽  
Inheritance Of Resistance ◽  
Resistant Parent ◽  
Bt Crops ◽  
Content Type

ABSTRACT Laboratory selection with Vip3Aa of a field-derived population of Heliothis virescens produced >2,040-fold resistance in 12 generations of selection. The Vip3Aa-selected (Vip-Sel)-resistant population showed little cross-resistance to Cry1Ab and no cross-resistance to Cry1Ac. Resistance was unstable after 15 generations without exposure to the toxin. F1 reciprocal crosses between Vip3Aa-unselected (Vip-Unsel) and Vip-Sel insects indicated a strong paternal influence on the inheritance of resistance. Resistance ranged from almost completely recessive (mean degree of dominance [h] = 0.04 if the resistant parent was female) to incompletely dominant (mean h = 0.53 if the resistant parent was male). Results from bioassays on the offspring from backcrosses of the F1 progeny with Vip-Sel insects indicated that resistance was due to more than one locus. The results described in this article provide useful information for the insecticide resistance management strategies designed to overcome the evolution of resistance to Vip3Aa in insect pests. IMPORTANCE Heliothis virescens is an important pest that has the ability to feed on many plant species. The extensive use of Bacillus thuringiensis (Bt) crops or spray has already led to the evolution of insect resistance in the field for some species of Lepidoptera and Coleoptera. The development of resistance in insect pests is the main threat to Bt crops. The effective resistance management strategies are very important to prolong the life of Bt plants. Lab selection is the key step to test the assumption and predictions of management strategies prior to field evaluation. Resistant insects offer useful information to determine the inheritance of resistance and the frequency of resistance alleles and to study the mechanism of resistance to insecticides.

scholarly journals Fatores de virulência de Bacillus thuringiensis: o que existe além das proteínas Cry

2012 ◽  
Vol 5 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Gislayne Trindade Vilas-Bôas ◽  
Rita C. Alvarez ◽  
Clelton A. Dos Santos ◽  
Laurival A. Vilas-Boas
Keyword(s):  
Biological Control ◽  
Bacillus Thuringiensis ◽  
Virulence Factors ◽  
Insect Pests ◽  
Cry Proteins ◽  
Control Programs ◽  
Wide Range ◽  
Vip Proteins ◽  
Bacterium Bacillus ◽  
And Control

As proteínas Cry produzidas pela bactéria entomopatogênica Bacillus thuringiensis Berliner são bem conhecidas devido a alta citotoxicidade que exibem a uma variedade de insetos-alvo. O modo de ação destas proteínas é específico e torna os produtos à base de B. thuringiensis os mais amplamente utilizados em programas de controle biológico de pragas na agricultura e de importantes vetores de doenças humanas. Contudo, embora as proteínas Cry sejam os fatores de virulência inseto-específico mais conhecidos, linhagens de B. thuringiensis apresentam também uma ampla gama de fatores de virulência, os quais permitem à bactéria atingir a hemolinfa e colonizar eficientemente o inseto hospedeiro. Dentre estes fatores, destacam-se as proteínas Vip, Cyt, enterotoxinas, hemolisinas, fosfolipases, proteases, enzimas de degradação, além das recentemente descritas parasporinas. Essa revisão aborda a ação desses fatores de virulência, bem como a caracterização e o controle da expressão de seus genes. Adicionalmente, são discutidos aspectos relacionados ao nicho ecológico da bactéria com ênfase nas características envolvidas com a biossegurança da utilização dos produtos à base de B. thuringiensis para o controle biológico de insetos-alvo. Virulence Factors of Bacillus thuringiensis Berliner: Something Beyond of Cry Proteins? Abstract. The Cry proteins produced by the entomopathogenic bacterium Bacillus thuringiensis Berliner are widely known due to its high toxicity against a variety of insects. The mode of action of these proteins is specific and becomes B. thuringiensis-based products the most used in biological control programs of insect pests in agriculture and of important human disease vectors. However, while the Cry proteins are the best-known insect-specific virulence factor, strains of B. thuringiensis show also a wide range of other virulence factors, which allow the bacteria to achieve the hemolymph and colonize efficiently the insect host. Among these factors, we highlight the Vip proteins, Cyt, enterotoxins, hemolysins, phospholipases, proteases and enzymes of degradation, in addition to the recently described parasporin. This review explores the action of these virulence factors, as well as, the characterization and control of expression of their genes. Additionally, we discuss aspects related to the ecological niche of the bacteria with emphasis on the characteristics involved in the biosafety of the use of B. thuringiensis-based products for biological control of target insects.

scholarly journals Isolation of Bacillus thuringiensis strains that contain Dipteran-specific cry genes from Ilha Bela (São Paulo, Brazil) soil samples

2012 ◽  
Vol 72 (2) ◽  
pp. 243-247 ◽  
Author(s):  
EB. Campanini ◽  
CC. Davolos ◽  
ECC. Alves ◽  
MVF. Lemos
Keyword(s):  
Biological Control ◽  
Bacillus Thuringiensis ◽  
Aedes Aegypti ◽  
Ribosomal Subunit ◽  
Soil Samples ◽  
Bacterial Isolates ◽  
Cry Genes ◽  
Cry Proteins ◽  
Crystal Proteins ◽  
Bacterium Bacillus

The entomophatogenic bacterium Bacillus thuringiensis produces crystal proteins, named Cry proteins which are encoded by the cry genes. This bacterium is used on biological control of important economical pests, as well as in the control of disease´s vectors, such as Aedes aegypti, a mosquito that transmits the dengue viruses. Isolates of this bacterium can be characterized by the content of cry genes and this prediction helps target different insect orders. In this research, we isolated 76 colonies of B. thuringiensis from 30 soil samples that were taken from Ilha Bela (SP, Brazil), a place where simulids are already biologically controlled by B. thuringiensis, to find bacterial isolates that were capable of controlling A. aegypti. The 16S ribosomal subunit genes of the selected isolates were sequenced, and the isolates were molecularly characterized based on their Dipteran-specific cry gene contents. Eight of the 76 isolates (10.52%) contained the cry4Aa, cry4Ba or cry10Aa genes, these isolates were carried out against A. aegypti larvae on bioassay. The presence or absence of specific cry genes was associated with the observed average larval mortalities. From the 76 isolates, seven (9.2%) were potentially able to control A. aegypti larvae. Therefore these are promising isolates for the biological control of A. aegypti larvae.

scholarly journals Toxicity of Bacillus thuringiensis-Derived Pesticidal Proteins Cry1Ab and Cry1Ba against Asian Citrus Psyllid, Diaphorina citri (Hemiptera)

Toxins ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 173 ◽  
Author(s):  
Maria Fernandez-Luna ◽  
Pavan Kumar ◽  
David Hall ◽  
Ashaki Mitchell ◽  
Michael Blackburn ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Asian Citrus Psyllid ◽  
Diaphorina Citri ◽  
Cry Toxins ◽  
Diverse Range ◽  
Additional Tool ◽  
Incurable Disease ◽  
Important Pest ◽  
Bacterium Bacillus ◽  
The Individual

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera), is an important pest of citriculture. The ACP vectors a bacterium that causes huanglongbing (HLB), a devastating and incurable disease of citrus. The bacterium Bacillus thuringiensis (Bt) produces multiple toxins with activity against a diverse range of insects. In efforts to provide additional control methods for the ACP vector of HLB, we identified pesticidal proteins derived from Bt for toxicity against ACP. The trypsin proteolytic profiles of strain-derived toxins were characterized. Strain IBL-00200, one of six strains with toxins shown to have basal activity against ACP was selected for liquid chromatography-mass spectrometry (LC-MS/MS) identification of the individual Cry toxins expressed. Toxicity assays with individual toxins derived from IBL-00200 were then performed. The activated form of the Cry toxins Cry1Ab and Cry1Ba were toxic to ACP with LC50 values of approximately 120 µg/mL. Disruption of the midgut epithelium was associated with the toxicity of both the IBL-00200-derived toxin mixture, and with Cry1Ba. With further optimization of the efficacy of Cry1Ab and Cry1Ba, these toxins may have practical utility against ACP. Bt toxins with activity against ACP may provide an additional tool for management of ACP and the associated HLB disease, thereby providing a more sustainable and environmentally benign approach than repeated application of broad-spectrum insecticides.

scholarly journals Lack of Detrimental Effects of Bacillus thuringiensis Cry Toxins on the Insect Predator Chrysoperla carnea: a Toxicological, Histopathological, and Biochemical Analysis

2006 ◽  
Vol 72 (2) ◽  
pp. 1595-1603 ◽  
Author(s):  
Ana Rodrigo-Simón ◽  
Ruud A. de Maagd ◽  
Carlos Avilla ◽  
Petra L. Bakker ◽  
Jos Molthoff ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Cell Damage ◽  
Specific Binding ◽  
Real Life ◽  
Chrysoperla Carnea ◽  
Green Lacewing ◽  
Cry Proteins ◽  
Cry Toxins

ABSTRACT The effect of Cry proteins of Bacillus thuringiensis on the green lacewing (Chrysoperla carnea) was studied by using a holistic approach which consisted of independent, complementary experimental strategies. Tritrophic experiments were performed, in which lacewing larvae were fed Helicoverpa armigera larvae reared on Cry1Ac, Cry1Ab, or Cry2Ab toxins. In complementary experiments, a predetermined amount of purified Cry1Ac was directly fed to lacewing larvae. In both experiments no effects on prey utilization or fitness parameters were found. Since binding to the midgut is an indispensable step for toxicity of Cry proteins to known target insects, we hypothesized that specific binding of the Cry1A proteins should be found if the proteins were toxic to the green lacewing. In control experiments, Cry1Ac was detected bound to the midgut epithelium of intoxicated H. armigera larvae, and cell damage was observed. However, no binding or histopathological effects of the toxin were found in tissue sections of lacewing larvae. Similarly, Cry1Ab or Cry1Ac bound in a specific manner to brush border membrane vesicles from Spodoptera exigua but not to similar fractions from green lacewing larvae. The in vivo and in vitro binding results strongly suggest that the lacewing larval midgut lacks specific receptors for Cry1Ab or Cry1Ac. These results agree with those obtained in bioassays, and we concluded that the Cry toxins tested, even at concentrations higher than those expected in real-life situations, do not have a detrimental effect on the green lacewing when they are ingested either directly or through the prey.

scholarly journals Insect Hsp90 Chaperone Assists Bacillus thuringiensis Cry Toxicity by Enhancing Protoxin Binding to the Receptor and by Protecting Protoxin from Gut Protease Degradation

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Blanca I. García-Gómez ◽  
Sayra N. Cano ◽  
Erika E. Zagal ◽  
Edgar Dantán-Gonzalez ◽  
Alejandra Bravo ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Receptor Binding ◽  
Insecticidal Activity ◽  
Insect Pests ◽  
Biotechnological Applications ◽  
Cry Proteins ◽  
Cry Toxins ◽  
Content Type ◽  
Hsp90 Chaperone ◽  
Protease Degradation

ABSTRACT Bacillus thuringiensis Cry proteins are pore-forming insecticidal toxins with specificity against different crop pests and insect vectors of human diseases. Previous work suggested that the insect host Hsp90 chaperone could be involved in Cry toxin action. Here, we show that the interaction of Cry toxins with insect Hsp90 constitutes a positive loop to enhance the performance of these toxins. Plutella xylostella Hsp90 (PxHsp90) greatly enhanced Cry1Ab or Cry1Ac toxicity when fed together to P. xylostella larvae and also in the less susceptible Spodoptera frugiperda larvae. PxHsp90 bound Cry1Ab and Cry1Ac protoxins in an ATP- and chaperone activity-dependent interaction. The chaperone Hsp90 participates in the correct folding of proteins and may suppress mutations of some client proteins, and we show here that PxHsp90 recovered the toxicity of the Cry1AbG439D protoxin affected in receptor binding, in contrast to the Cry1AbR99E or Cry1AbE129K mutant, affected in oligomerization or membrane insertion, respectively, which showed a slight toxicity improvement. Specifically, PxHsp90 enhanced the binding of Cry1AbG439D protoxin to the cadherin receptor. Furthermore, PxHsp90 protected Cry1A protoxins from degradation by insect midgut proteases. Our data show that PxHsp90 assists Cry1A proteins by enhancing their binding to the receptor and by protecting Cry protoxin from gut protease degradation. Finally, we show that the insect cochaperone protein PxHsp70 also increases the toxicity of Cry1Ac in P. xylostella larvae, in contrast to a bacterial GroEL chaperone, which had a marginal effect, indicating that the use of insect chaperones along with Cry toxins could have important biotechnological applications for the improvement of Cry insecticidal activity, resulting in effective control of insect pests. IMPORTANCE Bacillus thuringiensis took advantage of important insect cellular proteins, such as chaperones, involved in maintaining protein homeostasis, to enhance its insecticidal activity. This constitutes a positive loop where the concentrations of Hsp90 and Hsp70 in the gut lumen are likely to increase as midgut cells burst due to Cry1A pore formation action. Hsp90 protects Cry1A protoxin from degradation and enhances receptor binding, resulting in increased toxicity. The effect of insect chaperones on Cry toxicity could have important biotechnological applications to enhance the toxicity of Cry proteins to insect pests, especially those that show low susceptibility to these toxins.

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