Mode of action of Bacillus thuringiensis PS86Q3 strain in hymenopteran forest pests

The mode of action of Cry toxins has been described principally in lepidopteran insects as a multistep process. In this work we describe the mode of action of a Cry toxin active in the common pine sawfly Diprion pini (Hymenoptera, Diprionidae), considered a major forest pest in Europe. Strain PS86Q3...

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Bibliographic Details
Published in:Insect biochemistry and molecular biology 2001-07, Vol.31 (9), p.849-856
Main Authors: Garcia-Robles, Inmaculada, Sánchez, Jorge, Gruppe, Axel, Martı́nez-Ramı́rez, Amparo Consuelo, Rausell, Carolina, Real, Marı́a Dolores, Bravo, Alejandra
Format: Article
Language:English
Subjects:
Animals
Bacillus thuringiensis
Bacillus thuringiensis - isolation & purification
Bacillus thuringiensis - metabolism
Bacillus thuringiensis - physiology
Bacillus thuringiensis mode of action
Bacterial Proteins - metabolism
Bacterial Toxins
Biotin
Cephacia abietis
Cry toxin
Cry5
Diprion pini
Diprionidae
Endopeptidases - metabolism
Endotoxins - metabolism
Enzyme Activation
Europe
Hemolysin Proteins
Hymenoptera - microbiology
Larva
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Summary:The mode of action of Cry toxins has been described principally in lepidopteran insects as a multistep process. In this work we describe the mode of action of a Cry toxin active in the common pine sawfly Diprion pini (Hymenoptera, Diprionidae), considered a major forest pest in Europe. Strain PS86Q3 contains a long bipyramidal crystal composed of five major proteins. The N-terminal sequence shows that the 155 kDa protein corresponds to Cry5B toxin and the other proteins belong to the Cry5A subgroup. PCR analysis indicates the presence of cry5Ac and cry5Ba genes, suggesting that Cry5A protein should be Cry5Ac. Activation of protoxins with trypsin or with midgut content from D. pini and Cephacia abietis (Hymenoptera, Pamphiliidae) (spruce webspinning sawfly), another important hymenopteran forest pest, produced a single 75 kDa toxin that corresponded to Cry5A by N-terminal sequence and is responsible for the insecticidal activity. Homologous competition experiments with D. pini and C. abietis brush border membrane vesicles (BBMV) showed that the binding interaction of Cry5A is specific. Membrane potential measurements using a fluorescent dye indicate that Cry5A toxin at nM concentration caused immediate permeability changes in the BBMV isolated from both hymenopteran larvae. The initial response and the sustained permeability change are cationic as previously shown for Cry1 toxins. These results indicate that the hymenopteran specific Cry5A toxin exerts toxicity by a similar mechanism as Cry1 toxins.
ISSN:0965-1748
1879-0240
DOI:10.1016/S0965-1748(01)00030-3