DIVERSITY IN GUT MICROFLORA OF <i>Helicoverpa armigera</i> POPULATIONS FROM DIFFERENT REGIONS IN RELATION TO BIOLOGICAL ACTIVITY OF <i>Bacillus thuringiensis</i> δ‐ENDOTOXIN Cry1Ac

Paramasiva, Inakarla; Shouche, Yogesh S.; Kulkarni, Girish; Krishnayya, P. V.; Akbar, S M D; Sharma, H. C.

doi:10.1002/arch.21190

Cited by 15 publications

(10 citation statements)

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“…Survival of H. armigera larvae fed on diets with Bt proteins was directly proportional to the concentration of antibiotics in the artificial diet [11,36]. It was observed that the larvae gain weight when fed on diet containing antibiotic cocktail, and similar trend observed in L. dispar [10] and M. sexta raised on antibiotics attained more weight than insects reared on regular diet [37]. The increase in larval weight was probably due to elimination of microbes resulting in nutrient deficit, so that food intake was more to fulfill the nutrient loss.…”

Section: Discussionmentioning

confidence: 53%

“…Protease-producing midgut bacterial species belong to Bacillus sp., and the studies on their role in potentiation and/or detoxification of Bt toxins are under progress. Composition of gut microbes varies across crop host plants and locations [10]; however, there are some bacterial strains which are common in most of the populations of H. armigera. Information on bacterial strains involved in potentiation and/or detoxification of the Bt toxins will be useful globally to develop strategies to delay the development of resistance in the insect pests to Bt transgenic crops.…”

Section: Discussionmentioning

confidence: 99%

“…There exist varying controversies for the role of midgut microbes in the pathogenicity of Bt against insects. Tolerance to Cry1Ac in H. armigera might be due to the adaptation of H. armigera to Bt toxins through variation in midgut symbionts [10]. In the absence of midgut microbes, Bt does not kill the larvae of gypsy moth Lymantria dispar (L.), Vanessa cardui (L.), Manduca sexta (L.), and Pieris rapae (L.) and the contribution of gut bacteria to Bt susceptibility varies across a range of Lepidoptera [11,12].…”

Section: Introductionmentioning

confidence: 99%

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Elimination of Gut Microbes with Antibiotics Confers Resistance to Bacillus thuringiensis Toxin Proteins in Helicoverpa armigera (Hubner)

Visweshwar

Sharma

Akbar

et al. 2015

Appl Biochem Biotechnol

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Helicoverpa armigera is one of the most important pests worldwide. Transgenic crops with toxin genes from Bacillus thuringiensis (Bt) have been deployed on a large scale to control this pest. The insecticidal activity of Bt is probably influenced by the insect midgut microbes, which vary across crop hosts and locations. Therefore, we examined the role of gut microbes in pathogenicity of Bt toxins in the H. armigera. Antibiotic cocktail was used for the complete elimination of the H. armigera gut microbes. Activated Cry1Ac, Bt formulation, and transgenic cotton resulted in larval weight loss and increase in mortality, but pretreatment of larvae with antibiotic cocktail significantly decreased larval mortality and increased the larval weight gain. Activated Cry1Ac and Bt formulation inhibited the activity of proteases in midgut of H. armigera larvae but showed no such effect in the larvae pretreated with antibiotic cocktail. Five protease bands in activated Cry1Ac and two in Bt formulation-treated larvae were inhibited but no such effect in the larvae pretreated with antibiotic cocktail. Cry1Ac protein was detected in Bt/Cry1Ac protoxin-fed larval gut extract in the absence of antibiotic cocktail, but fewer in larvae pretreated with antibiotic cocktail. The activity of antioxidant enzymes and aminopeptidases increased in larvae fed on Bt toxin, but there was no significant increase in antioxidant enzymes in larvae reared on toxin protein in combination with antibiotic cocktail. The results suggest that gut microbes exercise a significant influence on the toxicity of Cry1Ac and Bt formulation in H. armigera larvae. The implications of these results have been discussed in relation to development of insect resistance to Bt transgenic crops deployed for pest management.

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Section: Discussionmentioning

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Elimination of Gut Microbes with Antibiotics Confers Resistance to Bacillus thuringiensis Toxin Proteins in Helicoverpa armigera (Hubner)

Visweshwar

Sharma

Akbar

et al. 2015

Appl Biochem Biotechnol

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“…Several studies have already shown that a higher tolerance to Bt is associated with a difference in bacterial community composition [ 32 , 33 ]. Nevertheless, whether changes in microbiota content are the cause of an increased tolerance or a consequence of Bt infection remains unclear.…”

Section: Introductionmentioning

confidence: 99%

Bacterial microbiota of Aedes aegypti mosquito larvae is altered by intoxication with Bacillus thuringiensis israelensis

et al. 2018

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BackgroundInsect microbiota is a dynamic microbial community that can actively participate in defense against pathogens. Bacillus thuringiensis (Bt) is a natural entomopathogen widely used as a bioinsecticide for pest control. Although Bt’s mode of action has been extensively studied, whether the presence of microbiota is mandatory for Bt to effectively kill the insect is still under debate. An association between a higher tolerance and a modified microbiota was already evidenced but a critical point remained to be solved: is the modified microbiota a cause or a consequence of a higher tolerance to Bt?MethodsIn this study we focused on the mosquito species Aedes aegypti, as no work has been performed on Diptera on this topic to date, and on B. thuringiensis israelensis (Bti), which is used worldwide for mosquito control. To avoid using antibiotics to cure bacterial microbiota, mosquito larvae were exposed to an hourly increasing dose of Bti during 25 hours to separate the most susceptible larvae dying quickly from more tolerant individuals, with longer survival.ResultsDenaturing gradient gel electrophoresis (DGGE) fingerprinting revealed that mosquito larval bacterial microbiota was strongly affected by Bti infection after only a few hours of exposure. Bacterial microbiota from the most tolerant larvae showed the lowest diversity but the highest inter-individual differences. The proportion of Bti in the host tissue was reduced in the most tolerant larvae as compared to the most susceptible ones, suggesting an active control of Bti infection by the host.ConclusionsHere we show that a modified microbiota is associated with a higher tolerance of mosquitoes to Bti, but that it is rather a consequence of Bti infection than the cause of the higher tolerance. This study paves the way to future investigations aiming at unraveling the role of host immunity, inter-species bacterial competition and kinetics of host colonization by Bti that could be at the basis of the phenotype observed in this study.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-2741-8) contains supplementary material, which is available to authorized users.

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“…Microbes have been documented to influence the susceptibility of lepidopteran insects targeted by Bt plants. Gut microbiota actually appear to be required for Bt susceptibility in lepidopteran pests [85][86][87][88][89]. Gut microbes also play a role in crop rotation resistance in D. v. virgifera, but the role of gut microbiota in Bt resistance and susceptibility is unknown [37].…”

Section: Microbes and Their Implications For Bt Resistancementioning

confidence: 99%

Rootworm management: status of GM traits, insecticides and potential new tools.

Ludwick¹,

Hibbard²

2017

CABI Reviews

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Western corn rootworm (Diabrotica virgifera virgifera LeConte) and northern corn rootworm (Diabrotica barberi (Smith and Lawrence)) are major pests of maize in the USA. These pests have been managed with a variety of tactics over the last century. Both Diabrotica spp. have adapted to crop rotation in different ways in certain regions of the USA as well as to some of the insecticides targeted at them. D. v. virgifera has adapted to more of the chemical control measures and transgenic control methods. Discussed in this review are the challenges associated with managing both species, and how current management strategies might be combined and implemented to help manage damage from these species. Also, we discuss the potential for new technologies, such as RNA interference, to be used in the future.

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DIVERSITY IN GUT MICROFLORA OF Helicoverpa armigera POPULATIONS FROM DIFFERENT REGIONS IN RELATION TO BIOLOGICAL ACTIVITY OF Bacillus thuringiensis δ‐ENDOTOXIN Cry1Ac

Cited by 15 publications

References 36 publications

Elimination of Gut Microbes with Antibiotics Confers Resistance to Bacillus thuringiensis Toxin Proteins in Helicoverpa armigera (Hubner)

Elimination of Gut Microbes with Antibiotics Confers Resistance to Bacillus thuringiensis Toxin Proteins in Helicoverpa armigera (Hubner)

Bacterial microbiota of Aedes aegypti mosquito larvae is altered by intoxication with Bacillus thuringiensis israelensis

Rootworm management: status of GM traits, insecticides and potential new tools.

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