Structural and functional diversity of bacillus thuringiensis toxins on animal, plant and microbial cells
- Autores: Ayda Khorramnejad
- Directores de la Tesis: Reza Talaei Hassanloui (dir. tes.), Baltasar Escriche (dir. tes.), Yolanda Bel Cortés (codir. tes.)
- Lectura: En la Universitat de València ( España ) en 2018
- Idioma: español
- Tribunal Calificador de la Tesis: Gholamreza Salehi (presid.), Solmaz Azimi (secret.), Javad Karimi (voc.)
- Programa de doctorado: Programa de Doctorado en Biomedicina y Biotecnología por la Universitat de València (Estudi General)
- Materias:
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- Resumen
Bacillus thuringiensis (Bt) is one of the most successful entomopathogens in biological control of pests. The identification of new Bt strains is a topical issue in order to discover novel Bt toxins to broaden the range of insecticidal activities and to manage insect resistance. Due to the importance of Bt, Iranian Bt strains were screened according to their toxicity against Plodia interpunctella. Strains with diverse larvicidal activity were characterized according to their gene content, protein composition, the spectrum of insecticidal and cytocidal activity against lepidopteran pests, the production of β-exotoxin, and the anti-microbial activity and biochemical effects on plant cells. As a result, due to high toxicity exhibited towards lepidopteran insect larvae and cell lines, and to the absence of β-exotoxin, the AzLp, IE-2 and IP-2 Bt strains were introduced as suitable candidates for development of new Bt based bio-insecticides. The inoculation of tomato plants with spore and crystal mixture of the selected Bt strains, increased the activity of antioxidant enzymes and induced resistance to probable pathogen invasions and to biotic and abiotic stress in the tomato plants, but no antimicrobial activities were recorded against phytopathogens such as the fungus Fusarium oxysporum subsp. lycopersici and or the bacteria Erwinia sp.
The gene content analyses of the highly insecticidal Bt strains conducted to the isolation of the cry1Ia38 gene from the IE-1 Bt strain. Subsequently, the gene was successfully cloned. Based on our results, Cry1Ia38 protein has a great potential for controlling Ostrinia nubilalis and Grapholita molesta. Due to the specific features of the Cry1I proteins, the formation of an oligomeric structure formed by Cry1Ia toxin monomers and the association between oligomerization and insecticidal activity of this protein, have been investigated. Based on our results, toxin oligomerization may not be widely generalized for the Cry1Ia toxins.
