How Bacillus thuringiensis has evolved specific toxins to colonize the insect world

Maagd, Ruud A. de; Bravo, Alejandra; Crickmore, N.

doi:10.1016/s0168-9525(01)02237-5

Cited by 553 publications

(444 citation statements)

References 45 publications

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“…21,25 The formation of toxin oligomer also has been postulated to be the result of the interaction of monomers that were bound to the cadherin receptor. 48 Our results clearly show differential association profiles for the oligomeric and monomeric forms of Cry1Ab toxin in cell membrane, the consequence of two distinct modes of interaction with the insect cells. Both monomers and oligomers were associated with S5 cells expressing BT-R 1 whereas no monomers, only oligomers, were associated with H5 cells devoid of the receptor (Figure 3a-d).…”

Section: Discussionmentioning

confidence: 57%

“…These findings contradict the notion that membrane-associated monomers are precursors to oligomer assembly. 48 Our studies are the first to demonstrate two distinct modes of interaction between Cry1Ab toxin and insect cells. One interaction is receptor independent and promotes assembly and insertion of toxin oligomers into cell membrane and the other involves univalent binding of toxin monomers to BT-R 1 , the latter of which leads to cell death.…”

Section: Discussionmentioning

confidence: 76%

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Cytotoxicity of Bacillus thuringiensis Cry1Ab toxin depends on specific binding of the toxin to the cadherin receptor BT-R1 expressed in insect cells

et al. 2005

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The specific role of cadherin receptors in cytotoxicity involving Cry toxins of Bacillus thuringiensis and their interactions with cell membrane has not been defined. To elucidate the involvement of toxin-membrane and toxinreceptor interactions in cytotoxicity, we established a cellbased system utilizing High Five insect cells stably expressing BT-R 1 , the cadherin receptor for Cry1Ab toxin. Cry1Ab toxin is incorporated into cell membrane in both oligomeric and monomeric form. Monomeric toxin binds specifically to BT-R 1 whereas incorporation of oligomeric toxin is nonspecific and lipid dependent. Toxin oligomers in the cell membrane do not produce lytic pores and do not kill insect cells. Rather, cell death correlates with binding of the Cry1Ab toxin monomer to BT-R 1 , which apparently activates a Mg 2 þ -dependent cellular signaling pathway.

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Section: Discussionmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 76%

Cytotoxicity of Bacillus thuringiensis Cry1Ab toxin depends on specific binding of the toxin to the cadherin receptor BT-R1 expressed in insect cells

et al. 2005

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“…The Cry toxins found in different Bacillus thuringiensis (Bt) strains cause mortality to susceptible insects by lysing the midgut epithelium cells [1,2]. In order to exert their toxic effect, a transition from crystal inclusion protoxins to membrane-inserted pores is required.…”

Section: Introductionmentioning

confidence: 99%

Permeability Changes of Manduca sexta Midgut Brush Border Membranes Induced by Oligomeric Structures of Different Cry Toxins

et al. 2006

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Abstract. The pore-formation activity of monomeric and oligomeric forms of different Cry1 toxins (from Cry1A to Cry1G) was analyzed by monitoring ionic permeability across Manduca sexta brush border membrane vesicles. The membrane vesicles were isolated from microvilli structures, showing a high enrichment of apical membrane markers and low intrinsic K + permeability. A fluorometric assay performed with 3,3¢-dipropylthiodicarbocyanine fluorescent probe, sensitive to changes in membrane potential, was used. Previously, it was suggested that fluorescence determinations with this dye could be strongly influenced by the pH, osmolarity and ionic strength of the medium. Therefore, we evaluated these parameters in control experiments using the K + -selective ionophore valinomycin. We show here that under specific ionic conditions changes in fluorescence can be correlated with ionic permeability without effects on osmolarity or ionic strength of the medium. It is extremely important to attenuate the background response due to surface membrane potential and the participation of the endogenous permeability of the membrane vesicles. Under these conditions, we analyzed the pore-formation activity induced by monomeric and oligomeric structures of different Cry1 toxins. The Cry1 toxin samples containing oligomeric structures correlated with high pore activity, in contrast to monomeric samples that showed marginal pore-formation activity, supporting the hypothesis that oligomer formation is a necessary step in the mechanism of action of Cry toxins.

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“…lifesci.sussex.ac.uk/home/Neil_Crickmore/Bt). Cry proteins have already been described as toxic to several insect from Lepidoptera, Diptera, Coleoptera, Hymenoptera, Homoptera, and Malophaga orders (Zhong et al, 2000;De Maagd et al, 2001;Castilhos-Fortes et al 2002;Martins et al, 2004;Nazarian et al, 2009;López-Pazos et al, 2009) and also to nematodes (Marroquin et al, 2000;Jouzani et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Two new Brazilian isolates of Bacillus thuringiensis toxic to Anticarsia gemmatalis (Lepidoptera: Noctuidae)

Fiúza¹,

Schünemann

Pinto

et al. 2012

Braz. J. Biol.

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Bacillus thuringiensis is a bacterium used for biopesticides production and pest-resistant plants due to the synthesis of protein crystals by cry genes, which are effective in controlling several insect orders such as Lepidoptera. This work aimed at the evaluation and characterisation of two new B. thuringiensis isolates active against A. gemmatalis (Hübner 1818) larvae, which is the soybean major pest. The results showed that Bt117-4 isolate amplified fragments corresponding to cry2 and cry9 genes, and synthesised protein fragments equivalent to 130, 90 and 45 kDa. The Bt3146-4 isolate amplified DNA fragments corresponding to cry9 gene and synthesised protein fragments of 70, 58 and 38 kDa. Transmission electron microscopy revealed the presence of protein crystals in both isolates. CL50 with Cry purified proteins from Bt117-4 and Bt3146-4, corresponded to 0.195 and 0.191 µg larvae-1, respectively. The two B. thuringiensis isolates selected in this study were effective to control velvetbean caterpillar at laboratory conditions. Field tests should be carried on to develop new biopesticides formulation as well for cry genes resource for Anticarsia gemmatalis resistant transgenic plants.

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How Bacillus thuringiensis has evolved specific toxins to colonize the insect world

Cited by 553 publications

References 45 publications

Cytotoxicity of Bacillus thuringiensis Cry1Ab toxin depends on specific binding of the toxin to the cadherin receptor BT-R1 expressed in insect cells

Cytotoxicity of Bacillus thuringiensis Cry1Ab toxin depends on specific binding of the toxin to the cadherin receptor BT-R1 expressed in insect cells

Permeability Changes of Manduca sexta Midgut Brush Border Membranes Induced by Oligomeric Structures of Different Cry Toxins

Two new Brazilian isolates of Bacillus thuringiensis toxic to Anticarsia gemmatalis (Lepidoptera: Noctuidae)

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