Variable Cross-Resistance to Cry11B from Bacillus thuringiensis subsp. jegathesan in Culex quinquefasciatus (Diptera: Culicidae) Resistant to Single or Multiple Toxins of Bacillus thuringienisis subsp.israelensis

1998 ◽  
Vol 64 (11) ◽  
pp. 4174-4179 ◽  
Author(s):  
Margaret C. Wirth ◽  
Armelle Delécluse ◽  
Brian A. Federici ◽  
William E. Walton
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Quinquefasciatus ◽  
Complex Mixture ◽  
Cross Resistance ◽  
Variable Cross ◽  
Bacterial Strains ◽  
Bacillus Thuringiensis Subsp ◽  
Cry Toxin

ABSTRACT A novel mosquitocidal bacterium, Bacillus thuringiensissubsp. jegathesan, and one of its toxins, Cry11B, in a recombinant B. thuringiensis strain were evaluated for cross-resistance with strains of the mosquito Culex quinquefasciatus that are resistant to single and multiple toxins of Bacillus thuringiensis subsp. israelensis. The levels of cross-resistance (resistance ratios [RR]) at concentrations which caused 95% mortality (LC95) betweenB. thuringiensis subsp. jegathesan and the different B. thuringiensis subsp.israelensis-resistant mosquito strains were low, ranging from 2.3 to 5.1. However, the levels of cross-resistance to Cry11B were much higher and were directly related to the complexity of the B. thuringiensis subsp. israelensis Cry toxin mixtures used to select the resistant mosquito strains. The LC95 RR obtained with the mosquito strains were as follows: 53.1 againstCq4D, which was resistant to Cry11A; 80.7 againstCq4AB, which was resistant to Cry4A plus Cry4B; and 347 against Cq4ABD, which was resistant to Cry4A plus Cry4B plus Cry11A. Combining Cyt1A with Cry11B at a 1:3 ratio had little effect on suppressing Cry11A resistance in Cq4D but resulted in synergism factors of 4.8 and 11.2 against strainsCq4AB and Cq4ABD, respectively; this procedure eliminated cross-resistance in the former mosquito strain and reduced it markedly in the latter strain. The high levels of activity ofB. thuringiensis subsp. jegathesan and B. thuringiensis subsp. israelensis, both of which contain a complex mixture of Cry and Cyt proteins, against Cry4- and Cry11-resistant mosquitoes suggest that novel bacterial strains with multiple Cry and Cyt proteins may be useful in managing resistance to bacterial insecticides in mosquito populations.

scholarly journals Lack of Cross-Resistance to Cry19A from Bacillus thuringiensis subsp. jegathesan in Culex quinquefasciatus (Diptera: Culicidae) Resistant to Cry Toxins from Bacillus thuringiensis subsp.israelensis

2001 ◽  
Vol 67 (4) ◽  
pp. 1956-1958 ◽  
Author(s):  
Margaret C. Wirth ◽  
Armelle Delécluse ◽  
William E. Walton
Keyword(s):  
Bacillus Thuringiensis ◽  
Culex Quinquefasciatus ◽  
Cross Resistance ◽  
Cry Toxins ◽  
Bacillus Thuringiensis Subsp

ABSTRACT Culex quinquefasciatus mosquitoes with high levels of resistance to single or multiple toxins from Bacillus thuringiensis subsp. israelensis were tested for cross-resistance to the Bacillus thuringiensis subsp.jegathesan polypeptide Cry19A. No cross-resistance was detected in mosquitoes that had been selected with the Cry11A, Cry4A and Cry4B, or Cry4A, Cry4B, Cry11A, and CytA toxins. A low but statistically significant level of cross-resistance, three to fourfold, was detected in the colony selected with Cry4A, Cry4B, and Cry11A. This cross-resistance was similar to that previously detected with B. thuringiensis subsp.jegathesan in the same colony. These data help explain the toxicity of B. thuringiensis subsp.jegathesan against the resistant colonies and indicate that the Cry19A polypeptide might be useful in managing resistance and/or as a component of synthetic combinations of mosquitocidal toxins.

scholarly journals Cadherin binding is not a limiting step for Bacillus thuringiensis subsp. israelensis Cry4Ba toxicity to Aedes aegypti larvae

2012 ◽  
Vol 443 (3) ◽  
pp. 711-717 ◽  
Author(s):  
Claudia Rodríguez-Almazán ◽  
Esmeralda Z. Reyes ◽  
Fernando Zúñiga-Navarrete ◽  
Carlos Muñoz-Garay ◽  
Isabel Gómez ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Aedes Aegypti ◽  
Lipid Bilayers ◽  
Insect Pests ◽  
Cry Toxins ◽  
Bacillus Thuringiensis Subsp ◽  
Limiting Step ◽  
Cry Toxin ◽  
Receptor Fragment

Bacillus thuringiensis subsp. israelensis produces three Cry toxins (Cry4Aa, Cry4Ba and Cry11Aa) that are active against Aedes aegypti larvae. The identification of the rate-limiting binding steps of Cry toxins that are used for insect control in the field, such as those of B. thuringiensis subsp. israelensis, should provide targets for improving insecticides against important insect pests. Previous studies showed that Cry11Aa binds to cadherin receptor fragment CR7–11 (cadherin repeats 7–11) with high affinity. Binding to cadherin has been proposed to facilitate Cry toxin oligomer formation. In the present study, we show that Cry4Ba binds to CR7–11 with 9-fold lower binding affinity compared with Cry11Aa. Oligomerization assays showed that Cry4Ba is capable of forming oligomers when proteolytically activated in vitro in the absence of the CR7–11 fragment in contrast with Cry11Aa that formed oligomers only in the presence of CR7–11. Pore-formation assays in planar lipid bilayers showed that Cry4Ba oligomers were proficient in opening ion channels. Finally, silencing the cadherin gene by dsRNA (double-stranded RNA) showed that silenced larvae were more tolerant to Cry11Aa in contrast with Cry4Ba, which showed similar toxic levels to those of control larvae. These findings show that cadherin binding is not a limiting step for Cry4Ba toxicity to A. aegypti larvae.

scholarly journals Monitoring resistance to Bacillus thuringiensis subsp. israelensis in the field by performing bioassays with each Cry toxin separately

2013 ◽  
Vol 108 (7) ◽  
pp. 894-900 ◽  
Author(s):  
Guillaume Tetreau ◽  
Renaud Stalinski ◽  
Jean-Philippe David ◽  
Laurence Després
Keyword(s):  
Bacillus Thuringiensis ◽  
Bacillus Thuringiensis Subsp ◽  
Cry Toxin
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