Sublethal effects of Bacillus thuringiensis Berliner in Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)
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2021-03-25
Autores
Motta, Amanda Cristiane Queiroz
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Universidade Estadual Paulista (Unesp)
Resumo
O Bacillus thuringiensis (Bt) tem se mostrado eficaz contra lepidópteros pragas, podendo ser utilizado como bioinseticida ou plantas transgênicas. As interações entre o organismo patogênico e o hospedeiro são geralmente caracterizadas pela patogenicidade e virulência. A atividade tóxica de Bt em lepidópteros-praga é mais bem elucidada para as proteínas Cry, em termos de patogenicidade e virulência. A virulência leva em consideração os efeitos subletais no organismo-alvo, o que pode contribuir para o conhecimento da dinâmica da população da praga. Os efeitos subletais são efeitos biológicos, fisiológicos, demográficos ou comportamentais em indivíduos ou populações que sobrevivem à exposição a alguma substância tóxica em dose ou concentração letal ou subletal. Os efeitos subletais nos lepidópteros podem ocorrer em todas as fases da vida. As proteínas Cry1Aa, Cr1Ab e Cry1Ac têm efeitos subletais em S. frugiperda devido à ligação reversível ao seu receptor. Os efeitos subletais do Bt em espécies de pragas podem ser avaliados em laboratório observando os parâmetros biológicos dos espécimes sobreviventes. O objetivo deste trabalho foi avaliar os efeitos subletais das proteínas Cry1Aa, Cry1Ab, Cry1Ac e de um produto comercial a base de Bt, em duas gerações de uma população suscetível de S. frugiperda. Após a submissão das larvas neonatas de S. frugiperda a CL25 estimada das proteínas e produto comercial, das larvas sobreviventes foram obtidos peso larval aos 7 e 10 dias de vida, peso de pré-pupa e deformação, peso pupal e deformação e sexo. Na fase adulta, 20 adultos foram utilizados para a montagem aleatória de casais e foram avaliados longevidade (dias de vida), fertilidade (% de ovos viáveis), fecundidade (número de ovos / dia) e número de adultos deformados. Para as análises proteômicas, dez casais de cada tratamento, e o mesmo para o controle, foram mantidos em gaiolas de PVC. Os ovos foram coletados de cada casal diariamente até a morte dos adultos e armazenados em freezer a -20ºC. Os mesmos procedimentos foram realizados para F2. A proteína foi extraída de cada amostra biológica usando o método fenólico e os peptídeos foram analisados em Synapt G2 HDMS (Waters, Manchester, UK). A análise de sobrevivência, independente do tratamento, não mostrou diferença em dez dias na F1. Os tratamentos apresentaram interferências negativas no desenvolvimento de S. frugiperda em F1 e F2. Dentre eles, o tratamento Cry1Ac apresentou interferência negativa em maior número de variáveis. As proteínas Cry não foram detectadas nos ovos de S. frugiperda em nenhuma das gerações avaliadas. Na segunda geração, foi identificado maior número total de proteínas nos ovos (1724) do que na primeira (1599). Em F1, 952 proteínas não redundantes foram identificadas e 989 proteínas não redundantes foram identificadas em F2. O produto comercial foi o tratamento que apresentou a maior quantidade de proteínas exclusivas em ambas as gerações, 74 na F1 e 210 na F2. Em sua maior parte, essas proteínas foram compartilhadas com Cry1Ac em ambas as gerações.
Among the effective biological control tactics applied against pest lepidopterans, the microorganism Bacillus thuringiensis (Bt) has been shown highly effective, and can be used as a bioinsecticide or transgenic plants. The interactions between the pathogenic organism and the host are generally characterized by pathogenicity and virulence. The toxic activity of Bt in pest lepidopterans is best elucidated for Cry proteins in terms of pathogenicity and virulence. Virulence takes into account the sublethal effects on the target organism, which can contribute to understanding the dynamics of the pest population. Sublethal effects are biological, physiological, demographic or behavioral effects in individuals or populations that survive exposure to some toxic substance in a lethal or sublethal dose or concentration. Sublethal effects on lepidoptera can occur at all stages of life. Cry1Aa, Cr1Ab and Cry1Ac proteins have sublethal effects on S. frugiperda due to reversible binding to their receptor. The sublethal effects of Bt in pest species can be evaluated in laboratory by assessing the biological parameters of the surviving specimens. The objective of this work was to evaluate the sublethal effects of proteins Cry1Aa, Cry1Ab, Cry1Ac and a commercial product based on Bt, in two generations of a susceptible population of S. frugiperda. After submitting neonate larvae of S. frugiperda to LC25 estimated for proteins and commercial product, to the survivor larvae were obtained larval weight at 7 and 10 days of life, pre-pupal weight and deformed, pupal weight and deformed and sex. In adulthood, 20 adults were used for the random assembly of couples and were evaluated longevity (days of life), fertility (% of viable eggs), fecundity (number of eggs/day) and number of adults deformed. To proteomic analyses ten couples for each treatment, and the same for the untreated, were set up in PVC cages. Eggs were collected from each couple daily until the death of adults and stored in a freezer at -20ºC. The same procedure was performed to F2. The protein was extracted from each biological sample using the phenolic method and peptides were analyzed in Synapt G2 HDMS (Waters, Manchester, UK). Survival analysis, independente of the treatment, did not showed difference over ten days in F1. The treatments showed negative interferences in the development of S. frugiperda in F1 and F2. Among them, the Cry1Ac treatment showed negative interference in the largest number of variables. The Cry proteins were not detected in the eggs of S. frugiperda in any of the evaluated generations. In the second generation, a greater total number of proteins in the eggs (1724) was identified than in the first (1599). In F1, 952 non-redundant proteins were identified and 989 non-redundant proteins were identified in F2. The commercial product was the treatment that presented the largest amount of exclusive proteins in both generations, 74 in F1 and 210 in F2. For the most part os these proteins were shared to Cry1Ac in both generations.
Among the effective biological control tactics applied against pest lepidopterans, the microorganism Bacillus thuringiensis (Bt) has been shown highly effective, and can be used as a bioinsecticide or transgenic plants. The interactions between the pathogenic organism and the host are generally characterized by pathogenicity and virulence. The toxic activity of Bt in pest lepidopterans is best elucidated for Cry proteins in terms of pathogenicity and virulence. Virulence takes into account the sublethal effects on the target organism, which can contribute to understanding the dynamics of the pest population. Sublethal effects are biological, physiological, demographic or behavioral effects in individuals or populations that survive exposure to some toxic substance in a lethal or sublethal dose or concentration. Sublethal effects on lepidoptera can occur at all stages of life. Cry1Aa, Cr1Ab and Cry1Ac proteins have sublethal effects on S. frugiperda due to reversible binding to their receptor. The sublethal effects of Bt in pest species can be evaluated in laboratory by assessing the biological parameters of the surviving specimens. The objective of this work was to evaluate the sublethal effects of proteins Cry1Aa, Cry1Ab, Cry1Ac and a commercial product based on Bt, in two generations of a susceptible population of S. frugiperda. After submitting neonate larvae of S. frugiperda to LC25 estimated for proteins and commercial product, to the survivor larvae were obtained larval weight at 7 and 10 days of life, pre-pupal weight and deformed, pupal weight and deformed and sex. In adulthood, 20 adults were used for the random assembly of couples and were evaluated longevity (days of life), fertility (% of viable eggs), fecundity (number of eggs/day) and number of adults deformed. To proteomic analyses ten couples for each treatment, and the same for the untreated, were set up in PVC cages. Eggs were collected from each couple daily until the death of adults and stored in a freezer at -20ºC. The same procedure was performed to F2. The protein was extracted from each biological sample using the phenolic method and peptides were analyzed in Synapt G2 HDMS (Waters, Manchester, UK). Survival analysis, independente of the treatment, did not showed difference over ten days in F1. The treatments showed negative interferences in the development of S. frugiperda in F1 and F2. Among them, the Cry1Ac treatment showed negative interference in the largest number of variables. The Cry proteins were not detected in the eggs of S. frugiperda in any of the evaluated generations. In the second generation, a greater total number of proteins in the eggs (1724) was identified than in the first (1599). In F1, 952 non-redundant proteins were identified and 989 non-redundant proteins were identified in F2. The commercial product was the treatment that presented the largest amount of exclusive proteins in both generations, 74 in F1 and 210 in F2. For the most part os these proteins were shared to Cry1Ac in both generations.
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Palavras-chave
lethal concentration, cry poteins, fall armyworm, molecular biology, Concentração letal, Proteínas cry, Lagarta do cartucho,, Biologia molecular