Coexpression of the silent cry2Ab27 together with cry1 genes in Bacillus thuringiensis subsp. aizawai SP41 leads to formation of amorphous crystal toxin and enhanced toxicity against Helicoverpa armigera

AbstractTomato plants in Nigeria were subjected to foliar sprays of Bacillus thuringiensis subsp. kurstaki (formulated as Dipel and Thuricide) and Baculovirus heliothis (Elcar), to which carbaryl, plus the adjuvants Tenac and Gustol were on occasion added, to test their effectiveness against Helicoverpa armigera (Hübner) and other lepidopterous larvae. H. armigera larvae were found susceptible to both pathogens. The 0·5 kg/ha and the 1·0 kg/ha applications of Bacillus thuringiensis gave good field control of the larvae, similar to that of carbaryl at 1·5 kg/ha. Bacillus and virus were compatible but not significantly more effective when combined than when applied separately. Combinations of bacillus and virus with carbaryl were also not significantly more effective than the pathogens applied separately. B. thuringiensis at 0·5 kg/ha applied with carbaryl at 0·5 kg/ha was as good as carbaryl at 1·5 kg/ha. Gustol and Tenac did not significantly increase the effectiveness of the pathogens.

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Impact of Bacillus thuringiensis Subsp. Kurstaki on Biology of Helicoverpa armigera

Pakistan Journal of Biological Sciences ◽

10.3923/pjbs.2003.615.621 ◽

2003 ◽

Vol 6 (6) ◽

pp. 615-621 ◽

Cited By ~ 6

Author(s):

Feeroza Khalique ◽

Khalique Ahmed .

Keyword(s):

Bacillus Thuringiensis ◽

Helicoverpa Armigera ◽

Bacillus Thuringiensis Subsp ◽

Helicoverpa Armígera

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Bacillus thuringiensis Bel Protein Enhances the Toxicity of Cry1Ac Protein to Helicoverpa armigera Larvae by Degrading Insect Intestinal Mucin

Applied and Environmental Microbiology ◽

10.1128/aem.00532-09 ◽

2009 ◽

Vol 75 (16) ◽

pp. 5237-5243 ◽

Cited By ~ 47

Author(s):

Shangling Fang ◽

Li Wang ◽

Wei Guo ◽

Xia Zhang ◽

Donghai Peng ◽

...

Keyword(s):

Bacillus Thuringiensis ◽

Helicoverpa Armigera ◽

Trichoplusia Ni ◽

Knockout Mutant ◽

Gene Encoding ◽

In Vitro Degradation ◽

Intestinal Mucin ◽

Helicoverpa Armígera ◽

Cry1ac Protein

ABSTRACT Bacillus thuringiensis has been used as a bioinsecticide to control agricultural insects. Bacillus cereus group genomes were found to have a Bacillus enhancin-like (bel) gene, encoding a peptide with 20 to 30% identity to viral enhancin protein, which can enhance viral infection by degradation of the peritrophic matrix (PM) of the insect midgut. In this study, the bel gene was found to have an activity similar to that of the viral enhancin gene. A bel knockout mutant was constructed by using a plasmid-free B. thuringiensis derivative, BMB171. The 50% lethal concentrations of this mutant plus the cry1Ac insecticidal protein gene were about 5.8-fold higher than those of the BMB171 strain. When purified Bel was mixed with the Cry1Ac protein and fed to Helicoverpa armigera larvae, 3 μg/ml Cry1Ac alone induced 34.2% mortality. Meanwhile, the mortality rate rose to 74.4% when the same amount of Cry1Ac was mixed with 0.8 μg/ml of Bel. Microscopic observation showed a significant disruption detected on the midgut PM of H. armigera larvae after they were fed Bel. In vitro degradation assays showed that Bel digested the intestinal mucin (IIM) of Trichoplusia ni and H. armigera larvae to various degrading products, similar to findings for viral enhancin. These results imply Bel toxicity enhancement depends on the destruction of midgut PM and IIM, similar to the case with viral enhancin. This discovery showed that Bel has the potential to enhance insecticidal activity of B. thuringiensis-based biopesticides and transgenic crops.

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