Participation of Valine 171 in α-Helix 5 of
            <i>Bacillus thuringiensis</i>
            Cry1Ab δ-Endotoxin in Translocation of Toxin into
            <i>Lymantria dispar</i>
            Midgut Membranes

Álzate, Óscar; Osorio, Cristina; Florez, Alvaro M.; Dean, Donald H.

doi:10.1128/aem.01428-10

Cited by 13 publications

(17 citation statements)

References 12 publications

(7 reference statements)

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“…Crystal proteins from Bt belonging to the insecticidal three-domain Cry toxin family have long been the subject of both protein improvement efforts and structure–function studies 16 17 18 19 . Another major class of Cry proteins belonging to the β pore-forming bacterial toxin family has received far less attention.…”

Section: Discussionmentioning

confidence: 99%

A transgenic approach for controlling Lygus in cotton

et al. 2016

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Lygus species of plant-feeding insects have emerged as economically important pests of cotton in the United States. These species are not controlled by commercial Bacillus thuringiensis (Bt) cotton varieties resulting in economic losses and increased application of insecticide. Previously, a Bt crystal protein (Cry51Aa2) was reported with insecticidal activity against Lygus spp. However, transgenic cotton plants expressing this protein did not exhibit effective protection from Lygus feeding damage. Here we employ various optimization strategies, informed in part by protein crystallography and modelling, to identify limited amino-acid substitutions in Cry51Aa2 that increase insecticidal activity towards Lygus spp. by >200-fold. Transgenic cotton expressing the variant protein, Cry51Aa2.834_16, reduce populations of Lygus spp. up to 30-fold in whole-plant caged field trials. One transgenic event, designated MON88702, has been selected for further development of cotton varieties that could potentially reduce or eliminate insecticide application for control of Lygus and the associated environmental impacts.

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Section: Discussionmentioning

confidence: 99%

A transgenic approach for controlling Lygus in cotton

et al. 2016

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“…These authors found that a conservative change to phenylalanine (W73F, W210F, W219F) produced mutant toxins 3.3, 1.5, and 2.3 times more toxic than the parental toxin. In a similar study [89], two α-helix 5 Cry1Ab mutants (V171C and L157C) with a 25-fold and 4-fold increase in toxicity toward Lymantria dispar, respectively, were reported.…”

Section: Evolution By Site-directed Mutagenesismentioning

confidence: 64%

Making 3D-Cry Toxin Mutants: Much More Than a Tool of Understanding Toxins Mechanism of Action

Vı́lchez

2020

Toxins

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3D-Cry toxins, produced by the entomopathogenic bacterium Bacillus thuringiensis, have been extensively mutated in order to elucidate their elegant and complex mechanism of action necessary to kill susceptible insects. Together with the study of the resistant insects, 3D-Cry toxin mutants represent one of the pillars to understanding how these toxins exert their activity on their host. The principle is simple, if an amino acid is involved and essential in the mechanism of action, when substituted, the activity of the toxin will be diminished. However, some of the constructed 3D-Cry toxin mutants have shown an enhanced activity against their target insects compared to the parental toxins, suggesting that it is possible to produce novel versions of the natural toxins with an improved performance in the laboratory. In this report, all mutants with an enhanced activity obtained by accident in mutagenesis studies, together with all the variants obtained by rational design or by directed mutagenesis, were compiled. A description of the improved mutants was made considering their historical context and the parallel development of the protein engineering techniques that have been used to obtain them. This report demonstrates that artificial 3D-Cry toxins made in laboratories are a real alternative to natural toxins.

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“…In this regard, it should be noted that unidentified characteristics of recombinant Bt-toxins in Bt-plants might affect binding and host specificity (Crickmore, 2005), while toxicity of recombinant Cry toxins may also be influenced by synergisms with endogenous plant metabolites or other extrinsic factors (Then, 2010). Further, the specificity of Bt-toxins is known to be largely determined by subtle differences in proteolytic processing (Haider et al, 1986), both toxicity and expression may be affected by single amino-acid changes in the polypeptide chain (Ward et al, 1988;Alzate et al, 2010), and differences in posttranslational modification mechanisms between prokaryotic and eukaryotic biological systems may influence the toxic potential of transgenic proteins (Franck-Oberaspach and Keller, 1997).…”

Section: Discussionmentioning

confidence: 99%

Chronic Responses ofDaphnia magnaUnder Dietary Exposure to Leaves of a Transgenic (Event MON810) Bt–Maize Hybrid and its Conventional Near-Isoline

Holderbaum

Cuhra

Wickson

et al. 2015

Journal of Toxicology and Environmental Health, Part A

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Insect resistance is the second most common trait globally in cultivated genetically modified (GM) plants. Resistance is usually obtained by introducing into the plant's genome genes from the bacterium Bacillus thuringiensis (Bt) coding for insecticidal proteins (Cry proteins or toxins) that target insect pests. The aim of this study was to examine the hypothesis that a chronic, high-dose dietary exposure to leaves of a Bt-maize hybrid (GM event MON810, expressing a transgenic or recombinant Cry1Ab toxin), exerted no adverse effects on fitness parameters of the aquatic nontarget organism Daphnia magna (water flea) when compared to an identical control diet based on leaves of the non-GM near-isoline. Cry1Ab was immunologically detected and quantified in GM maize leaf material used for Daphnia feed. A 69-kD protein near Bt's active core-toxin size and a 34-kD protein were identified. The D. magna bioassay showed a resource allocation to production of resting eggs and early fecundity in D. magna fed GM maize, with adverse effects for body size and fecundity later in life. This is the first study to examine GM-plant leaf material in the D. magna model, and provides of negative fitness effects of a MON810 maize hybrid in a nontarget model organism under chronic, high dietary exposure. Based upon these results, it is postulated that the observed transgenic proteins exert a nontarget effect in D. magna and/or unintended changes were produced in the maize genome/metabolome by the transformation process, producing a nutritional difference between GM-maize and non-GM near-isoline.

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Participation of Valine 171 in α-Helix 5 of Bacillus thuringiensis Cry1Ab δ-Endotoxin in Translocation of Toxin into Lymantria dispar Midgut Membranes

Cited by 13 publications

References 12 publications

A transgenic approach for controlling Lygus in cotton

A transgenic approach for controlling Lygus in cotton

Making 3D-Cry Toxin Mutants: Much More Than a Tool of Understanding Toxins Mechanism of Action

Chronic Responses ofDaphnia magnaUnder Dietary Exposure to Leaves of a Transgenic (Event MON810) Bt–Maize Hybrid and its Conventional Near-Isoline

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