Toward mosquito control with a green alga: expression of Cry toxins of Bacillus thuringiensis subsp. israelensis (Bti) in the chloroplast of Chlamydomonas

Aedes aegypti is a crucial vector for human diseases, such as yellow fever, dengue, chikungunya, and Zika viruses. Today, a major challenge throughout the globe is the insufficient availability of antiviral drugs and vaccines against arboviruses, and toxins produced by Bacillus thuringiensis (Bt) are still used as biological agents for mosquito control. The use of Cry toxins to kill insects mainly depends on the interaction between Cry toxins and important toxin receptors, such as alkaline phosphatase (ALP). In this study, we investigated the function of A. aegypti C-type lectin-20 (CTL-20) in the tolerance of Cry toxins. We showed that recombinant CTL-20 protein interacted with both Cry11Aa and ALP1 by the Far-Western blot and ELISA methods, and CTL-20 bound to A. aegypti larval brush border membrane vesicles (BBMVs). Binding affinity of CTL-20 to ALP1 was higher than that of Cry11Aa to ALP1. Furthermore, the survival rate of A. aegypti larvae fed with Cry11Aa toxin mixed with recombinant CTL-20 fusion protein was significantly increased compared with that of the control larvae fed with Cry11Aa mixed with thioredoxin. Our novel results suggest that midgut proteins like CTLs may interfere with interactions between Cry toxins and toxin receptors by binding to both Cry toxins and receptors to alter Cry toxicity.

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

Biochemical Journal ◽

10.1042/bj20111579 ◽

2012 ◽

Vol 443 (3) ◽

pp. 711-717 ◽

Cited By ~ 29

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.

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Environmental and socioeconomic effects of mosquito control in Europe using the biocide Bacillus thuringiensis subsp. israelensis (Bti)

The Science of The Total Environment ◽

10.1016/j.scitotenv.2020.137800 ◽

2020 ◽

Vol 724 ◽

pp. 137800 ◽

Cited By ~ 4

Author(s):

Carsten A. Brühl ◽

Laurence Després ◽

Oliver Frör ◽

Chandrashekhar D. Patil ◽

Brigitte Poulin ◽

...

Keyword(s):

Bacillus Thuringiensis ◽

Mosquito Control ◽

Bacillus Thuringiensis Subsp

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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

Applied and Environmental Microbiology ◽

10.1128/aem.67.4.1956-1958.2001 ◽

2001 ◽

Vol 67 (4) ◽

pp. 1956-1958 ◽

Cited By ~ 7

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.

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Lack of Resistance in Aedes vexans Field Populations After 36 Years of Bacillus thuringiensis subsp. Israelensis Applications in the Upper Rhine Valley, Germany

Journal of the American Mosquito Control Association ◽

10.2987/17-6694.1 ◽

2018 ◽

Vol 34 (2) ◽

pp. 154-157 ◽

Cited By ~ 9

Author(s):

Norbert Becker ◽

Mario Ludwig ◽

Tianyun Su

Keyword(s):

Bacillus Thuringiensis ◽

Large Scale ◽

Mosquito Control ◽

World Health ◽

Aedes Vexans ◽

Widespread Application ◽

Bacillus Thuringiensis Subsp ◽

Rhine Valley ◽

Health Organization ◽

Upper Rhine

ABSTRACT Bacillus thuringiensis subsp. israelensis (Bti) has been widely and solely used against floodwater mosquitoes, mostly Aedes vexans, for 36 years in the Upper Rhine Valley by the German Mosquito Control Association. During this period, almost 5,000 tons of Bti formulations were applied to an area of approximately 400,000 ha. To investigate a possible resistance development after such a long-term and widespread application of Bti, the susceptibility of Ae. vexans larvae to Bti in 3 untreated (Lake Constance) and 6 treated areas on both sides of the Rhine within the Upper Rhine Valley was assessed by bioassays following World Health Organization guidelines. Comparing log-probit analyses, it was shown that neither the median lethal concentration (LC50 values) nor slopes of the probit lines of bioassays of the larvae deriving from treated and untreated areas showed significant differences. These results have been confirmed by resistance ratios, which varied from 0.80 to 1.12 in all tests. The results provided the evidence that no restistance in the target species Ae. vexans has developed in the areas of the Upper Rhine Valley, despite the large-scale use of Bti for 36 years.

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