Resistance to Toxins from Bacillus thuringiensis subsp. kurstaki Causes Minimal Cross-Resistance to B. thuringiensis subsp. aizawai in the Diamondback Moth (Lepidoptera: Plutellidae) †

Insecticidal proteins from Bacillus thuringiensis (Bt) are used widely in sprays and transgenic crops to control insect pests. However, evolution of resistance by pests can reduce the efficacy of Bt toxins. Here we analyzed resistance to Bt toxins Cry1Ac and Cry1Fa in the diamondback moth (Plutella xylostella), one of the world’s most destructive pests of vegetable crops. We used CRISPR/Cas9 gene editing to create strains with knockouts of the ATP-binding cassette (ABC) transporter genes PxABCC2, PxABCC3, or both. Bioassay results show that knocking out either gene alone caused at most 2.9-fold resistance but knocking out both caused >10,320-fold resistance to Cry1Ac and 380-fold resistance to Cry1Fa. Cry1Ac resistance in the double knockout strain was recessive and genetically linked with the PxABCC2/PxABCC3 loci. The results provide insight into the mechanism of cross-resistance to Cry1Fa in diamondback moth. They also confirm previous work with this pest showing that mutations disrupting both genes cause higher resistance to Cry1Ac than mutations affecting either PxABCC2 or PxABCC3 alone. Together with previous work, the results here highlight the value of using single and multiple gene knockouts to better understand the independent and synergistic effects of putative Bt toxin receptors on resistance to Bt toxins.

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Cross-Resistance to Bacillus thuringiensis Toxin Cry1Ja in a Strain of Diamondback Moth Adapted to Artificial Diet

Journal of Invertebrate Pathology ◽

10.1006/jipa.2000.4941 ◽

2000 ◽

Vol 76 (1) ◽

pp. 81-83 ◽

Cited By ~ 19

Author(s):

Bruce E. Tabashnik ◽

Kenneth W. Johnson ◽

James T. Engleman ◽

James A. Baum

Keyword(s):

Bacillus Thuringiensis ◽

Artificial Diet ◽

Diamondback Moth ◽

Cross Resistance ◽

Bacillus Thuringiensis Toxin

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Insect resistance to Bacillus thuringiensis: uniform or diverse?

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1998.0327 ◽

1998 ◽

Vol 353 (1376) ◽

pp. 1751-1756 ◽

Cited By ~ 93

Author(s):

B. E. Tabashnik ◽

Y. Liu ◽

T. Malvar ◽

D. G. Heckel ◽

L. Masson ◽

...

Keyword(s):

Bacillus Thuringiensis ◽

Insect Resistance ◽

Diamondback Moth ◽

Genetically Engineered ◽

Cross Resistance ◽

Recessive Inheritance ◽

Insecticidal Proteins ◽

Bt Toxins ◽

Evolutionary Pathways ◽

Genetically Engineered Crops

Resistance to the insecticidal proteins produced by the soil bacterium Bacillus thuringiensis (Bt) has been documented in more than a dozen species of insect. Nearly all of these cases have been produced primarily by selection in the laboratory, but one pest, the diamondback moth ( Plutella xylostella ), has evolved resistance in open–field populations. Insect resistance to Bt has immediate and widespread significance because of increasing reliance on Bt toxins in genetically engineered crops and conventional sprays. Furthermore, intense interest in Bt provides an opportunity to examine the extent to which evolutionary pathways to resistance vary among and within species of insect. One mode of resistance to Bt is characterized by more than 500–fold resistance to at least one Cry1A toxin, recessive inheritance, little or no cross–resistance to Cry1C, and reduced binding of at least one Cry1A toxin. Analysis of resistance to Bt in the diamondback moth and two other species of moth suggests that although this particular mode of resistance may be the most common, it is not the only means by which insects can attain resistance to Bt.

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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

Applied and Environmental Microbiology ◽

10.1128/aem.64.11.4174-4179.1998 ◽

1998 ◽

Vol 64 (11) ◽

pp. 4174-4179 ◽

Cited By ~ 41

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.

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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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