Single concentration tests show synergism among Bacillus thuringiensis subsp. israelensis toxins against the malaria vector mosquito Anopheles albimanus

Fernandez-Luna, Maria Teresa; Tabashnik, Bruce E.; Lanz‐Mendoza, Humberto; Bravo, Alejandra; Soberón, Mário; Miranda-Ríos, Juan

doi:10.1016/j.jip.2010.03.007

Cited by 40 publications

(39 citation statements)

References 17 publications

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“…It is important to note that although Cyt1Aa is toxic to A. aegypti larvae, toxicity is low compared with other Cry mosquitocidal proteins [10]. Also, it was recently shown that in other mosquito species as Anopheles albimanus Cyt1Aa is not toxic but it still synergized Cry4Ba and Cry11Aa in this mosquito species [14]. It could be possible that the major role of Cyt1Aa in toxicity against dipteran larvae is its synergistic capacity to enhance Cry toxicity rather than its toxicity itself.…”

Section: Discussionmentioning

confidence: 99%

Membrane binding and oligomer membrane insertion are necessary but insufficient for Bacillus thuringiensis Cyt1Aa toxicity

et al. 2014

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Bacillus thuringiensis Cyt proteins are pore-forming toxins that have insecticidal activity mainly against dipteran insects. However, certain Cyt proteins have toxicity to some insect orders, but not toxicity of Cyt1Aa against lepidopteran larvae has been found. Insect specificity has been proposed to rely in specific binding to certain lipids on the brush border membrane of midgut cells since no protein receptors have been described so far. To determine the molecular basis of Cyt1Aa insect specificity we compared different steps of Cyt1Aa mode of action in a susceptible insect as the dipteran Aedes aegypti and also in the non-susceptible lepidopteran Manduca sexta. Our data shows that the lack toxicity of Cyt1Aa to M. sexta larvae does not rely on protoxin processing, membrane binding interaction, and oligomerization of Cyt1Aa since these steps were similar in the two insect species analyzed.

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Section: Discussionmentioning

confidence: 99%

Membrane binding and oligomer membrane insertion are necessary but insufficient for Bacillus thuringiensis Cyt1Aa toxicity

et al. 2014

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“…Such features also effectively suppressed resistance toward B. thuringiensis subsp. israelensis in mosquito populations (2)(3)(4)(5). Although no sustained resistance to B. thuringiensis subsp.…”

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confidence: 99%

Identification and Characterization of Three Previously Undescribed Crystal Proteins from Bacillus thuringiensis subsp. jegathesan

Sun

Zhao

Xia

et al. 2013

Appl Environ Microbiol

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The total protoxin complement in the parasporal body of mosquitocidal strain, Bacillus thuringiensis subsp. jegathesan 367, was determined by use of a polyacrylamide gel block coupled to mass spectrometry. A total of eight protoxins were identified from this strain, including five reported protoxins (Cry11Ba, Cry19Aa, Cry24Aa, Cry25Aa, and Cyt2Bb), as well as three previously undescribed (Cry30Ca, Cry60Aa, and Cry60Ba) in this isolate. It was interesting that the encoding genes of three new protoxins existed as cry30Ca-gap-orf2 and cry60Ba-gap-cry60Aa. The cry30Ca and a downstream orf2 gene were oriented in the same direction and separated by 114 bp, and cry60Ba was located 156 bp upstream from and in the same orientation to cry60Aa. The three new protoxin genes were cloned from B. thuringiensis subsp. jegathesan and expressed in an acrystalliferous strain under the control of cyt1A gene promoters and the STAB-SD stabilizer sequence. Recombinant strain containing only cry30Ca did not produce visible inclusion under microscope observation, while that containing both cry30Ca and orf2 could produce large inclusions. Cry60Aa and Cry60Ba synthesized either alone or together in the acrystalliferous host could yield large inclusions. In bioassays using the fourth-instar larvae of Culex quinquefasciatus, Cry60Aa and Cry60Ba alone or together had estimated 50% lethal concentrations of 2.9 to 7.9 g/ml; however, Cry30Ca with or without ORF2 was not toxic to this mosquito.

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“…In contrast, Cyt1A proteins were found to synergize toxicity of Cry4A and Cry4B toxins, Cry10Aa and Cry11Aa in mosquito larvae (Chang et al, 1993;Wu et al, 1994;Wirth et al, 2004;Fernández-Luna et al, 2010). In fact, Wirth et al (2004) reported that when Cry toxins from Bti were combined with B. sphaericus, in the presence or absence of Cyt1Aa, synergistically increased toxicity and an expanded host range were observed.…”

Section: Combinatorial Effects Of Cry Toxins With Bacteria-derived Comentioning

confidence: 99%

Specificity and Combinatorial Effects of Bacillus Thuringiensis Cry Toxins in the Context of GMO Environmental Risk Assessment

Hilbeck

Otto

2015

Front. Environ. Sci.

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Stacked GM crops expressing up to six Cry toxins from Bacillus thuringiensis (Bt) are today replacing the formerly grown single-transgene GM crop varieties. Stacking of multiple Cry toxins not only increase the environmental load of toxins but also raise the question on how possible interactions of the toxins can be assessed for risk assessment, which is mandatory for GM crops. However, no operational guidelines for a testing strategy or testing procedures exist. From the developers point of view, little data testing for combinatorial effects of Cry toxins is necessary as the range of possibly affected organisms focuses on pest species and no evidence is claimed to exist pointing to combinatorial effects on non-target organisms. We have examined this rationale critically using information reported in the scientific literature. To do so, we address the hypothesis of narrow specificity of Cry toxins subdivided into three underlying different conceptual conditions (i) "efficacy" in target pests as indicator for "narrow specificity," (ii) lack of reported adverse effects of Cry toxins on non-target organisms, and (iii) proposed modes of action of Cry toxins (or the lack thereof) as mechanisms underlying the reported activity/efficacy/specificity of Cry toxins. Complementary to this information, we evaluate reports about outcomes of combinatorial effect testing of Cry toxins in the scientific literature and relate those findings to the practice of environmental risk assessment of Bt-crops in general and of stacked Bt-events in particular.

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Single concentration tests show synergism among Bacillus thuringiensis subsp. israelensis toxins against the malaria vector mosquito Anopheles albimanus

Cited by 40 publications

References 17 publications

Membrane binding and oligomer membrane insertion are necessary but insufficient for Bacillus thuringiensis Cyt1Aa toxicity

Membrane binding and oligomer membrane insertion are necessary but insufficient for Bacillus thuringiensis Cyt1Aa toxicity

Identification and Characterization of Three Previously Undescribed Crystal Proteins from Bacillus thuringiensis subsp. jegathesan

Specificity and Combinatorial Effects of Bacillus Thuringiensis Cry Toxins in the Context of GMO Environmental Risk Assessment

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