Interactions between Cry1Ac, Cry2Ab, and Cry1Fa Bacillus thuringiensis toxins in the cotton pests Helicoverpa armigera (Hübner) and Earias insulana (Boisduval)

Ibargutxi, María A.; Muñoz, Delia; Escudero, Íñigo Ruiz de; Caballero, Primitivo

doi:10.1016/j.biocontrol.2008.07.003

Cited by 43 publications

(38 citation statements)

References 30 publications

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“…For the case of Cry1F þ Cry1Ac proteins, the assumed environmental response is that of response addition in which each toxin acts independently and does not interact at the site of toxin action. Additivity is an appropriate assumption for this case [15], because, even though a degree of cross-resistance of Cry1F and Cry1Ac is observed for some susceptible species [16], the effect seems to be associated with secondary receptors, and the effect on susceptibility is slight [17]. The methodology employed considered the relevant laboratory toxicity data, the expression of these data in terms of mixture toxicity, the data on in planta expression of the Cry1F and Cry1Ac proteins, the translation of expression levels into environmental loads and exposure concentrations, and the development of the msPAF.…”

Section: Methodsmentioning

confidence: 99%

“…For Cry1F, published studies [15,[18][19][20][21] were augmented with regulatory-compliant data for Cry1F protein expressed from cry1F(synpro), the chimeric synthetic gene expressed in WideStrike cotton [22], and cry1F [23,24] (Table 1). For Cry1Ac, published studies [15,17,18,20,[24][25][26][27][28][29][30][31] were augmented with regulatory-compliant data for Cry1Ac protein expressed from cry1Ac(synpro), the chimeric synthetic gene expressed in WideStrike cotton [32] ( Table 2). The activities of the proteins expressed by these various genes and expression systems were considered equivalent ( [33]; http://www.health.gov.au/internet/ogtr/publishing.…”

Section: Laboratory Toxicity Datamentioning

confidence: 99%

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A mixture toxicity approach for environmental risk assessment of multiple insect resistance genes

Wolt

2011

Enviro Toxic and Chemistry

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Multiple substance considerations applied to chemical mixtures in ecological risk assessments can be logically extended to nontarget organism (NTO) risk assessment for pyramided trait crops expressing multiple insect resistance genes. A case instance is developed that considers a two-protein pyramid of Cry1F and Cry1Ac synthetic proteins expressed in cotton (Gossypium hirsutum L.). A mixture toxicity approach was used to arrive at the aggregated multisubstance potentially affected fraction (msPAF) of NTOs that may be at risk from exposure to Cry1F + Cry1Ac cotton in representative-use environments. Development of the msPAF for putative susceptible NTOs considered laboratory toxicity data for Lepidoptera expressed in terms of additive mixture toxicity as well as data on in planta expression of the Cry1F and Cry1Ac proteins and their translation into environmental loads and exposure concentrations. The msPAF based on tier 1 estimated environmental concentrations (EECs) and toxicity to Lepidoptera species-used as surrogate data for adverse effects to a putative susceptible species-provided a highly conservative estimate of effects on beneficial species and therefore is a ready means to conduct screening-level NTO risk assessments for pyramided crops.

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Section: Methodsmentioning

confidence: 99%

Section: Laboratory Toxicity Datamentioning

confidence: 99%

A mixture toxicity approach for environmental risk assessment of multiple insect resistance genes

Wolt

2011

Enviro Toxic and Chemistry

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“…Also combinations of Cry toxins have proven to be a very useful strategy employed in boosting efficacy and fighting resistance (Jurat-Fuentes et al 2003;Kaur 2006;Avisar et al 2009). The combination of Cry1Ac and Cry2Ab showed a synergistic effect to Helicoverpa armigera (Ibargutxi et al 2008). …”

Section: Use Of Synergism Between Bt Products or Between Bt Products mentioning

confidence: 97%

“…lifesci.sussex.ac.uk/home/Neil_Crickmore/Bt/). Of these a large number have been heterologously expressed and found to be either independently (Song et al 2003;Gonzalez-Cabrera et al 2006;Ibargutxi et al 2008;Xue et al 2008;Hu et al 2010) or in combination toxic to specific insect species in one or more orders.…”

Section: Continuous Search For Bt Strains Expressing Toxins With Imprmentioning

confidence: 99%

Bacillus thuringiensis Applications in Agriculture

George

Crickmore

2012

Bacillus Thuringiensis Biotechnology

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Bacillus thuringiensis (Bt) and its insecticidal toxins have been used in agronomical pest control for decades. The mechanism of action of Bt toxins on insect pest involves specific molecular interactions which makes Bt a popular choice for pest control. The specificity of action of Bt toxins reduces the concern of adverse effects on non-target species, a concern which remains with chemical insecticides. Different strains of Bt are known to express different classes of toxins which in turn target different insects. Bt and its toxins can be formulated into powder or liquid sprays or expressed in transgenic plants. To maximize the effect of Bt toxins, multiple toxins are often combined when making Bt formulations or expressed in transgenic plants. Though Bt is a very effective biological control agent, there are concerns over the development of resistance by insect species and also the narrow spectrum of activity of individual toxins. To address these concerns, new strains of Bt expressing novel toxins are actively sought and existing toxins are genetically modified for improved activity.

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“…Poncet et al (1995) found synergistic and additive effects of combined Cry toxins in three different mosquito species. Both Ibargutxi et al (2008) and Yunus et al (2011) reported synergistic effects of Cry1Ac and Cry2A toxins on Earias insulana, the spotted bollworm. In contrast, in two studies involving Helicoverpa armigera larvae and testing a similar combination of Cry1Ac and Cry1F, Ibargutxi et al (2008) found no synergistic interaction while Charkrabarti et al (1998) did (Table 2).…”

Section: Combinatorial Effects Of Different Cry Toxinsmentioning

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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Interactions between Cry1Ac, Cry2Ab, and Cry1Fa Bacillus thuringiensis toxins in the cotton pests Helicoverpa armigera (Hübner) and Earias insulana (Boisduval)

Cited by 43 publications

References 30 publications

A mixture toxicity approach for environmental risk assessment of multiple insect resistance genes

A mixture toxicity approach for environmental risk assessment of multiple insect resistance genes

Bacillus thuringiensis Applications in Agriculture

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

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