Quantification of Cry1Ac and Cry1F &lt;I&gt;Bacillus thuringiensis&lt;/I&gt; Insecticidal Proteins in Selected Transgenic Cotton Plant Tissue Types

Siebert, Melissa; Patterson, T. G.; Gilles, G. J.; Nolting, S. P.; Braxton, L. B.; Leonard, B. R.; Duyn, John W. Van; Lassiter, R. B.

doi:10.1603/029.102.0357

Cited by 50 publications

(29 citation statements)

References 33 publications

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“…However, unlike our results showing similar seasonal declines of about threefold in Cry1Ac and Cry2Ab in DP 164 B2RF, previous studies with other cultivars found that the seasonal decline in toxin concentration was generally less for Cry2Ab (35)(36)(37) than Cry1Ac (38)(39)(40)(41)(42). In any case, seasonal declines in the concentration of Bt toxins could be an important factor affecting redundant killing because there is extensive variation among cotton cultivars in patterns of production of Bt toxins (43).…”

Section: Discussioncontrasting

confidence: 98%

Potential shortfall of pyramided transgenic cotton for insect resistance management

Brévault

Heuberger

Zhang

et al. 2013

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

155

222

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To delay evolution of pest resistance to transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt), the "pyramid" strategy uses plants that produce two or more toxins that kill the same pest. In the United States, this strategy has been adopted widely, with two-toxin Bt cotton replacing one-toxin Bt cotton. Although two-toxin plants are likely to be more durable than one-toxin plants, the extent of this advantage depends on several conditions. One key assumption favoring success of two-toxin plants is that they kill insects selected for resistance to one toxin, which is called "redundant killing." Here we tested this assumption for a major pest, Helicoverpa zea, on transgenic cotton producing Bt toxins Cry1Ac and Cry2Ab. Selection with Cry1Ac increased survival on two-toxin cotton, which contradicts the assumption. The concentration of Cry1Ac and Cry2Ab declined during the growing season, which would tend to exacerbate this problem. Furthermore, analysis of results from 21 selection experiments with eight species of lepidopteran pests indicates that some cross-resistance typically occurs between Cry1A and Cry2A toxins. Incorporation of empirical data into simulation models shows that the observed deviations from ideal conditions could greatly reduce the benefits of the pyramid strategy for pests like H. zea, which have inherently low susceptibility to Bt toxins and have been exposed extensively to one of the toxins in the pyramid before two-toxin plants are adopted. For such pests, the pyramid strategy could be improved by incorporating empirical data on deviations from ideal assumptions about redundant killing and cross-resistance. (Résumé d'auteur

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Section: Discussioncontrasting

confidence: 98%

Potential shortfall of pyramided transgenic cotton for insect resistance management

Brévault

Heuberger

Zhang

et al. 2013

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

155

222

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“…The study findings are consistent with the Mendelian inheritance of a single dominant locus such as the Cry1Ab gene. In addition, these results suggest that in the leaf tissues, expression of the concentration of Bt δ-endotoxins was inherited stably and follows the Mendelian segregation as observed in the crosses of Bt maize events and the non-Bt F 2 generations (Siebert et al, 2009;Mugo et al, 2011). In the contrast analysis, crosses between Bt and nonBt F 1 generations had no significant effect on the mean concentration of Bt δ-endotoxins.…”

Section: Discussionmentioning

confidence: 54%

“…The effectiveness and sustainability of Bt transgenic technology in the control of stem borers will depend on the levels of expression of the Bt δ-endotoxins (Kranthi et al, 2005;Olsen et al, 2005;Dong and Li, 2007;Siebert et al, 2009). In addition, gene expression levels should be sufficient in appropriate plant tissues and express in successive generations (Kranthi et al, 2005;Olsen et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Quantification of Bt δ-endotoxins in leaf tissues of tropical Bt maize populations

Murenga¹,

Danson²,

Mugo³

et al. 2012

Afr. J. Biotechnol.

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In Kenya, stem borers destroy an estimated 13.5% of farmers' annual maize harvest. Maize transformed using Bacillus thuringiensis (Bt) derived genes controls stem borers without negative effects to humans, livestock or the environment. The effectiveness and sustainability of Bt transgenic technology in the control of stem borers depends on the levels of concentration of the Bt δ-endotoxins in plant tissues. Kenya introduced Bt maize events to test the efficacy of Bt maize in controlling stem borers, and to develop high-yielding and locally adapted Bt maize germplasm for farmers. The objective of this study was to assess under greenhouse conditions the concentration levels of Bt δ-endotoxins in the leaf tissues of the parents, the F 1 , and the F 2:3 populations of tropical maize, as a measure of stability and sustainability. Kenya introduced Bt maize events to test the efficacy of Bt maize in controlling stem borers, and to develop high-yielding and locally adapted Bt maize germplasm for farmers. The objective of this study was to assess under greenhouse conditions the concentration levels of Bt δ-endotoxins in the leaf tissues of the parents, the F1, and the F2:3 populations of tropical maize, as a measure of stability and sustainability. Two public Bt maize lines (Event 216 and Event 223) containing the cry1Ab::ubi gene were crossed with two non-Bt maize inbred lines, CML144 and CML159, to assess how the concentrations of Bt δ-endotoxins are transmitted from parents to F 1 and to F 2 generations. The mean concentration of Bt δ-endotoxins (μg/g) was 4.93 and 4.63 in Events 216 and 223 respectively. As expected, F 1 generations of all the crosses had similar concentrations of Bt δ-endotoxins. However, the F 2 generations showed a spread of concentrations. These findings may imply that genotypes with a higher mean concentration of Bt δ-endotoxins also have a lower level of plant damage traits expressed. In addition, these observations indicate that the cry1Ab gene was dominant and was inherited following the Mendelian segregation and that Events 216 and 223 could be utilized as reliable sources of resistance to stem borers in maize breeding programmes.

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“…The data used describe the season-long pattern of Cry1F and Cry1Ac expression and distribution for WideStrike cotton grown over 13 location-years in representative upland cottongrowing regions in the United States and Australia [34][35][36]. These data describing mean expression by location-year were considered to be independent and identically distributed and therefore were combined by tissue type and growth stage to generate the grand mean and range of Cry1F and Cry1Ac tissue concentrations.…”

Section: Protein Expression and Environmental Loadmentioning

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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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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Quantification of Cry1Ac and Cry1F <I>Bacillus thuringiensis</I> Insecticidal Proteins in Selected Transgenic Cotton Plant Tissue Types

Cited by 50 publications

References 33 publications

Potential shortfall of pyramided transgenic cotton for insect resistance management

Potential shortfall of pyramided transgenic cotton for insect resistance management

Quantification of Bt δ-endotoxins in leaf tissues of tropical Bt maize populations

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

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