Pore-forming properties of the Bacillus thuringiensis toxin Cry9Ca in Manduca sexta brush border membrane vesicles

Brunet, Jean-Frédéric; Vachon, Vincent; Juteau, Marc; Rie, Jeroen Van; Larouche, Geneviève; Vincent, C.; Schwartz, Jean-Louis; Laprade, Raynald

doi:10.1016/j.bbamem.2010.02.006

Cited by 10 publications

(4 citation statements)

References 46 publications

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“…However, it is unclear how important post binding cleavage is for toxicity. Pore formation may not be dependent on post binding cleavage, and protease activity at the membrane of epithelial cells may inhibit pore formation [ 68 , 69 , 70 ]. Additional research is needed to clarify post binding events to assess the potential for Cry modification to stimulate pore formation.…”

Section: Cleavage Site Modificationsmentioning

confidence: 99%

Bt Toxin Modification for Enhanced Efficacy

Deist

Rausch

Fernandez-Luna

et al. 2014

Toxins

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Insect-specific toxins derived from Bacillus thuringiensis (Bt) provide a valuable resource for pest suppression. Here we review the different strategies that have been employed to enhance toxicity against specific target species including those that have evolved resistance to Bt, or to modify the host range of Bt crystal (Cry) and cytolytic (Cyt) toxins. These strategies include toxin truncation, modification of protease cleavage sites, domain swapping, site-directed mutagenesis, peptide addition, and phage display screens for mutated toxins with enhanced activity. Toxin optimization provides a useful approach to extend the utility of these proteins for suppression of pests that exhibit low susceptibility to native Bt toxins, and to overcome field resistance.

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Section: Cleavage Site Modificationsmentioning

confidence: 99%

Bt Toxin Modification for Enhanced Efficacy

Deist

Rausch

Fernandez-Luna

et al. 2014

Toxins

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show abstract

“…The Cry9Aa insecticidal proteins show a wide spectrum of insecticidal activity against Lepidoptera pests such as Plutella xylostella, Exorista larvarum, and Spodoptera exigua. − Similar to most Cry proteins, Cry9 proteins have pore-forming activity, and the minimal active fragment of Cry9Aa containing all three conserved domains was identified . The bioassay of Cry9Eb and Cry9Ee proteins against Cry1Ac-resistant P.…”

Section: Introductionmentioning

confidence: 99%

Bacillus thuringiensis Cry9Aa Insecticidal Protein Domain I Helices α3 and α4 Are Two Core Regions Involved in Oligomerization and Toxicity

He,

Yang,

Soberón

et al. 2024

J. Agric. Food Chem.

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Bacillus thuringiensis Cry9 proteins show high insecticidal activity against different lepidopteran pests. Cry9 could be a valuable alternative to Cry1 proteins because it showed a synergistic effect with no cross-resistance. However, the pore-formation region of the Cry9 proteins is still unclear. In this study, nine mutations of certain Cry9Aa helices α3 and α4 residues resulted in a complete loss of insecticidal activity against the rice pest Chilo suppressalis; however, the protein stability and receptor binding ability of these mutants were not affected. Among these mutants, Cry9Aa-D121R, Cry9Aa-D125R, Cry9Aa-D163R, Cry9Aa-E165R, and Cry9Aa-D167R are unable to form oligomers in vitro, while the oligomers formed by Cry9Aa-R156D, Cry9Aa-R158D, and Cry9Aa-R160D are unstable and failed to insert into the membrane. These data confirmed that helices α3 and α4 of Cry9Aa are involved in oligomerization, membrane insertion, and toxicity. The knowledge of Cry9 pore-forming action may promote its application as an alternative to Cry1 insecticidal proteins.

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“…The activated toxin binds to receptors on the insect gut epithelium. Conformational changes in the toxin result in insertion into the gut epithelial membrane, pore formation, and epithelial cell lysis through osmotic disruption [ 17 – 19 ]. In susceptible species, toxicity results in gut paralysis, reduced feeding, and extensive damage to epithelial cells, ultimately resulting in death of the insect [ 20 – 22 ].…”

Section: Introductionmentioning

confidence: 99%

Modification of Cry4Aa toward Improved Toxin Processing in the Gut of the Pea Aphid, Acyrthosiphon pisum

et al. 2016

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Aphids are sap-sucking insects (order: Hemiptera) that cause extensive damage to a wide range of agricultural crops. Our goal was to optimize a naturally occurring insecticidal crystalline (Cry) toxins produced by the soil-dwelling bacterium Bacillus thuringiensis for use against the pea aphid, Acyrthosiphon pisum. On the basis that activation of the Cry4Aa toxin is a rate-limiting factor contributing to the relatively low aphicidal activity of this toxin, we introduced cathepsin L and cathepsin B cleavage sites into Cry4Aa for rapid activation in the aphid gut environment. Incubation of modified Cry4Aa and aphid proteases in vitro demonstrated enhanced processing of the toxin into the active form for some of the modified constructs relative to non-modified Cry4Aa. Aphids fed artificial diet with toxin at a final concentration of 125 μg/ml showed enhanced mortality after two days for one of the four modified constructs. Although only modest toxin improvement was achieved by use of this strategy, such specific toxin modifications designed to overcome factors that limit aphid toxicity could be applied toward managing aphid populations via transgenic plant resistance.

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Pore-forming properties of the Bacillus thuringiensis toxin Cry9Ca in Manduca sexta brush border membrane vesicles

Cited by 10 publications

References 46 publications

Bt Toxin Modification for Enhanced Efficacy

Bt Toxin Modification for Enhanced Efficacy

Bacillus thuringiensis Cry9Aa Insecticidal Protein Domain I Helices α3 and α4 Are Two Core Regions Involved in Oligomerization and Toxicity

Modification of Cry4Aa toward Improved Toxin Processing in the Gut of the Pea Aphid, Acyrthosiphon pisum

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