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IMMUNE PRIMING – A PHENOTYPIC PROTECTION TO BACILLUS THURINGIENSIS IN TRIBOLIUM CASTANEUM

Bacillus thuringiensis is a spore-forming entomopathogenic bacterium widely used in the biological pest management of different, mainly grain and leaf-feeding dipterans, lepidopterans and coleopterans. The mechanism of microbe-induced insect mortality is based on the production of Cry toxins, crystalline proteins characterized by a high level of entomocidal specificity. Although B. thuringiensis has been successfully used for several decades in Cry toxin preparations and/or transgenic Bt crops, the major threat to its use is the appearance of insect resistance developed on an evolutionary scale and at the genetic level by mutations in insect pests affecting the Cry toxins’ mode of action or its activation. Besides evolutionary resistance, immune priming, a phenomenon emerging in different insects as a form of immune memory induced by various pathogens, could be identified as an alternative mechanism of resistance at the phenotypic level. We tested the ability of the red flour beetle, Tribolium castaneum, to mount an immune priming response to three different Bacillus thuringiensis strains known for their entomocidal activity against this pest. We show that immune protection can be triggered by oral uptake of bacteria-derived components in two of the three bacterial strains used here. Additionally, using a full-factorial experimental design, we show a certain level of specificity in the immune resistance towards the two bacterial strains. Our results contribute to the growing body of knowledge on pest resistance and offer a new perspective on how to deal with this problem in the framework of biological pest control.

Bacillus thuringiensis, Tribolium castaneum, resistance, immune priming, specificity

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