Uso de vírus e Bacillus thuringiensis Berliner no controle de Thyrinteina arnobia (Stoll) (Lepidoptera: Geometridae)
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Data
2017-05-31
Autores
Horta, André Ballerini [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O Brasil é atualmente líder mundial em produtividade no setor florestal graças ao eucalipto. Os plantios de eucalipto sofrem com severos ataques de insetos-praga, cujos danos comprometem seriamente a produtividade. O controle biológico é a principal estratégia adotada pelas empresas do setor florestal, envolvendo sistemas de monitoramento das populações de insetos-praga. Um dos mais importantes grupos de desfolhadores é o dos lepidópteros desfolhadores. Espécies nativas brasileiras se adaptaram às plantações de eucalipto ao longo dos anos e a mais notável é a lagarta parda do eucalipto, Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae). Com ampla distribuição no território brasileiro, esta espécie se caracteriza pelos surtos nos períodos secos do ano, quando encontra condições favoráveis para expressar seu elevado potencial reprodutivo, causando severas desfolhas em grandes extensões. Medidas de controle são frequentemente necessárias, sendo realizadas pulverizações aéreas de bioinseticidas a base de Bacillus thuringiensis (Berliner, 1915) e liberações de inimigos naturais. Entretanto, epizootias virais podem ser observadas como reguladores naturais de tais populações. Neste contexto, o presente trabalho teve por objetivos: (I) a análise da toxicidade de seis diferentes proteínas Cry1 de B. thuringiensis sobre populações de T. arnobia e seu efeito na emergência de vírus latentes nestas populações; (II) sequenciamento do genoma completo, análise filogenética e caracterização ultraestrutural de um cypovirus encontrado em lagartas de T. arnobia. Os resultados obtidos mostram que doses subletais de proteínas Cry1 podem ter influência na ativação de vírus latentes presentes nas populações de T. arnobia, conduzindo a um quadro onde a mortalidade observada em diferentes níveis é ligada às infecções virais associadas à toxicidade das proteínas Cry1. Ainda, as análises do cypovirus encontrado revelaram sua proximidade com outros vírus pertencentes à espécie cypovirus 14. Dessa forma, de acordo com as normas definidas pelo Comitê Internacional em Taxonomia de Vírus, este foi nomeado Thyrinteina arnobia cypovirus 14. O gene que codifica a poliedrina, principal proteína na composição dos poliedros observados, foi clonado com sucesso em um baculovirus recombinante, cuja infecção em linhagens celulares de insetos resultou na produção de cristais proteicos no citoplasma das células infectadas. Este dado indica a aptidão dos poliedros deste cypovirus como nanocarreadores para outras proteínas fusionadas à poliedrina em estudos e aplicações biotecnológicas. Estudos futuros avaliarão ainda o potencial deste cypovirus no controle de populações de T. arnobia a campo, podendo se tornar mais uma ferramenta para a proteção dos plantios de eucalipto brasileiros.
Brazil is nowadays the global leader in productivity at forest sector due to Eucalyptus. Eucalyptus plantations suffer severe attacks from insect-pests, whose damages compromise seriously the productivity. Biological control is the main strategy adopted by the forest companies, involving pest population monitoring systems. One of the most important defoliators group is the lepidopterous defoliators. Native Brazilian species had adapted to the eucalyptus plantations over the years and the most remarkable one is the eucalyptus brown looper, Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae). Spread all over Brazil’s territory, this species is characterized by the outbreaks during the dry periods of the year, when it has good conditions to express its high reproductive potential, causing severe defoliation in large extensions. Control measures are frequently necessary, thus aerial spraying with Bacillus thuringiensis (Berliner, 1915) based bioinseticides and releases of natural enemies are carried out. However, sometimes viral epizootics can be observed acting as natural regulators for such populations. The interactions between B. thuringiensis and native entomopathogenic viruses are unknown to T.arnobia in eucalyptus plantations. In this context, the present work had as objectives: (I) the toxicity analysis of six different Cry1 proteins of B. thuringiensis on populations of T. arnobia and their effect on the emergence of latent viruses in these populations; (II) complete genome sequencing, phylogenetic analysis and ultrastructural characterization of a cypovirus found in T. arnobia caterpillars. The results show that sublethal doses of Cry1 proteins may have an influence on the activation of latent viruses present in the T. arnobia populations, leading to a context where the mortality observed at different levels is linked to the viral infections associated with the toxicity of Cry1 proteins. In addition, the analysis of the cypovirus found revealed its proximity to other viruses belonging to the cypovirus 14 species. Thus, according to the standards defined by the International Committee on Virus Taxonomy, it was named Thyrinteina arnobia cypovirus 14. The gene encoding polyhedrin, the main protein in the composition of the polyhedra observed, was successfully cloned in a recombinant baculovirus, whose infection in insect cell lines resulted in the production of protein crystals in the cytoplasm of the infected cells. This data indicates the suitability of the polyhedra of this cypovirus as nanocarriers for other proteins fused to polyhedrin in studies and biotechnological applications. Future studies will also evaluate the potential of this cypovirus in the control of T. arnobia populations at the field and may become another tool for the protection of Brazilian eucalyptus plantations.
Brazil is nowadays the global leader in productivity at forest sector due to Eucalyptus. Eucalyptus plantations suffer severe attacks from insect-pests, whose damages compromise seriously the productivity. Biological control is the main strategy adopted by the forest companies, involving pest population monitoring systems. One of the most important defoliators group is the lepidopterous defoliators. Native Brazilian species had adapted to the eucalyptus plantations over the years and the most remarkable one is the eucalyptus brown looper, Thyrinteina arnobia (Stoll, 1782) (Lepidoptera: Geometridae). Spread all over Brazil’s territory, this species is characterized by the outbreaks during the dry periods of the year, when it has good conditions to express its high reproductive potential, causing severe defoliation in large extensions. Control measures are frequently necessary, thus aerial spraying with Bacillus thuringiensis (Berliner, 1915) based bioinseticides and releases of natural enemies are carried out. However, sometimes viral epizootics can be observed acting as natural regulators for such populations. The interactions between B. thuringiensis and native entomopathogenic viruses are unknown to T.arnobia in eucalyptus plantations. In this context, the present work had as objectives: (I) the toxicity analysis of six different Cry1 proteins of B. thuringiensis on populations of T. arnobia and their effect on the emergence of latent viruses in these populations; (II) complete genome sequencing, phylogenetic analysis and ultrastructural characterization of a cypovirus found in T. arnobia caterpillars. The results show that sublethal doses of Cry1 proteins may have an influence on the activation of latent viruses present in the T. arnobia populations, leading to a context where the mortality observed at different levels is linked to the viral infections associated with the toxicity of Cry1 proteins. In addition, the analysis of the cypovirus found revealed its proximity to other viruses belonging to the cypovirus 14 species. Thus, according to the standards defined by the International Committee on Virus Taxonomy, it was named Thyrinteina arnobia cypovirus 14. The gene encoding polyhedrin, the main protein in the composition of the polyhedra observed, was successfully cloned in a recombinant baculovirus, whose infection in insect cell lines resulted in the production of protein crystals in the cytoplasm of the infected cells. This data indicates the suitability of the polyhedra of this cypovirus as nanocarriers for other proteins fused to polyhedrin in studies and biotechnological applications. Future studies will also evaluate the potential of this cypovirus in the control of T. arnobia populations at the field and may become another tool for the protection of Brazilian eucalyptus plantations.
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Palavras-chave
Eucalyptus, Cypovirus, Cry proteins, Proteínas cry