Prospecção de moléculas com potencial inseticida derivadas de genótipos de mandioca (Manihot esculenta Crantz)
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Data
2019-05-03
Autores
Barilli, Diandro Ricardo
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Universidade Estadual Paulista (Unesp)
Resumo
As plantas apresentam diversos metabólitos secundários em seus mecanismos de defesa que podem ser produzidos de forma constitutiva ou induzida. Esses metabólitos apresentam propriedades antinutritivas, repelentes ou tóxicas a insetos herbívoros. Plantas de mandioca são conhecidas por sua rusticidade e produção de compostos de defesa contra herbívoros tais como os compostos cianogênicos. Mesmo assim, plantas de mandioca podem ser colonizadas e utilizadas por uma série de insetos específicos. Na busca de formas de reduzir o impacto negativo desses insetos sobre as plantas de mandioca, genótipos que resultam em interferências negativas sobre o desenvolvimento de insetos foram identificados. Porém, pouco se sabe a respeito da composição química das folhas de plantas de mandioca e, sobretudo, dos genótipos com maiores efeitos negativos no desenvolvimento dos insetos. Com isso, o presente trabalho foi realizado para conhecer diferenças químicas entre as folhas de mandioca de genótipos selecionados de forma a esclarecer como a composição química desses genótipos pode ser relacionada com as influências observadas no desenvolvimento de insetos pragas. Foi realizada avaliação do desenvolvimento do herbívoro-modelo Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) alimentado com seis genótipos de mandioca (IAC-14, IAC-90, IAC-12, IAC-Caapora, Baianinha e MEcu 72). A análise da composição química desses genótipos foi realizada pela quantificação de fenóis totais e saponinas esteroidais. Análises por GC-MS foram realizadas para os genótipos IAC-Caapora, Baianinha e MEcu 72. Foi realizado estudo para avaliar se a infestação por S. frugiperda induz alterações na concentração dos fitormônios, ácido abscísico, ácido salicílico e ácido jasmônico, e de duas moléculas associadas à via do ácido jasmônico (ácido 12-oxofitodienoico - OPDA e jasmonil-isoleucina) bem como na concentração de cianeto (CN). Por fim, foram realizadas análises por LC-MS e quantificação da atividade hemaglutinante (AH) nos seis genótipos. O genótipo MEcu 72 resultou nos piores índices nutricionais e, juntamente com Baianinha, nos piores índices reprodutivos de S. frugiperda. As análises de GC-MS resultaram na detecção de 58 metabólitos e 21 desses metabólitos apresentaram diferença significativa entre os três genótipos avaliados. Os metabólitos myo-inositol-2-monofosfato, os ácidos p-cumárico, clorogênico e p-hidroxibenzoico, duas formas de ácido octadecadienoico e n-hexacosano foram detectados em maior abundância no genótipo MEcu 72 ou Baianinha em relação a IAC-Caapora. A quantificação de fitormônios indica que o genótipo MEcu 72 apresenta concentrações constitutivas de fitormônios maiores que os demais genótipos. Após herbivoria, mudanças na concentração dos fitormônios e de moléculas associadas às rotas de biossínte dos fitormônios ocorreram, porém, sem um padrão específico, variando principalmente em função do genótipo testado. Após a herbivoria, nenhum dos genótipos avaliados alterou a concentração de CN, o que demonstra que as alterações nas concentrações de fitormônios induzidas por herbivoria não estão relacionadas com as rotas de biossíntese de CN. Por meio da análise do LC-MS, o genótipo MEcu 72, considerado um padrão de resistência para os insetos sugadores, apresentou 10 metabólitos exclusivos e um metabólito com abundância de 2 a 5 vezes superior aos demais e maior atividade hemaglutinante. Os possíveis papéis dessas moléculas nas interferências negativas causadas sobre o desenvolvimento dos insetos pragas são discutidas.
Plants have several secondary metabolites that may be associated with plant-herbivore interactions. Some of these metabolites are antinutrient, repellent or toxic to herbivores. Cassava plants are rustic and produce defense compounds against herbivores such as cyanogenic compounds. Nevertheless, cassava plants can be colonized and used by a number of specific herbivores. In search of ways to reduce the negative impact of these insects on cassava plants, genotypes that result in negative interferences on the development of insects were identified. However, there is a lack of information about the chemical composition of the cassava leaves, mainly, from genotypes with large negative effects on insect development. Thus, the present work was carried out to evaluate the chemical differences between cassava leaves of selected genotypes in order to clarify how the chemical composition of these genotypes can be related to the influences observed in the development of insect pests. The development of the model herbivore Spodoptera frugiperda (JE Smith, 1797) (Lepidoptera: Noctuidae) was assessed by feeding larvae with leaves from six cassava genotypes (IAC-14, IAC-90, IAC-12, IAC-Caapora, Baianinha and MEcu 72). We performed the analysis of the chemical composition of these genotypes by quantification of total phenols and steroidal saponins. Analyzes by GC-MS were performed for the IAC-Caapora, Baianinha and MEcu 72 genotypes. A study was carried out to evaluate if S. frugiperda infestation induces changes in the concentration of the phytohormones, abscisic acid, salicylic acid and jasmonic acid, two molecules associated with the pathway of jasmonic acid (12-oxophitodienoic acid - OPDA and jasmonyl isoleucine) as well of cyanide (CN). Finally, analysis by LC-MS and quantification of hemagglutinating activity (AH) were performed in the six genotypes. The MEcu 72 genotype resulted in the worst nutritional indexes and, along with Baianinha, the worst reproductive indexes of S. frugiperda. The GC-MS analyzes resulted in the detection of 58 metabolites and 21 of these metabolites presented significant difference among the three evaluated genotypes. We detected myo-inositol-2-monophosphate, p-coumaric, chlorogenic and p-hydroxybenzoic acids, two forms of octadecadienoic acid and n-hexacosan in greater abundance in the MEcu 72 or Baianinha genotypes in relation to IAC-Caapora. MEcu 72 presents higher levels of constitutive phytohormones than the other genotypes. Herbivory caused changes in the levels of phytohormones and molecules associated with phytohormone pathways varing mainly according to the genotype tested, however, without a specific pattern. After herbivory, none of the evaluated genotypes altered the concentration of CN, which suggests that changes in herbivory-induced phytohormone concentrations are not related to CN biosynthesis pathway. By the LC-MS analyzes, the MEcu 72 genotype, a resistance standard for sap sucking insects, we found 10 exclusive metabolites and a metabolite with abundance 2 to 5 fold superior to the others and greater hemagglutinating activity. The possible roles of these molecules in the negative interferences caused on the development of insect pests are discussed.
Plants have several secondary metabolites that may be associated with plant-herbivore interactions. Some of these metabolites are antinutrient, repellent or toxic to herbivores. Cassava plants are rustic and produce defense compounds against herbivores such as cyanogenic compounds. Nevertheless, cassava plants can be colonized and used by a number of specific herbivores. In search of ways to reduce the negative impact of these insects on cassava plants, genotypes that result in negative interferences on the development of insects were identified. However, there is a lack of information about the chemical composition of the cassava leaves, mainly, from genotypes with large negative effects on insect development. Thus, the present work was carried out to evaluate the chemical differences between cassava leaves of selected genotypes in order to clarify how the chemical composition of these genotypes can be related to the influences observed in the development of insect pests. The development of the model herbivore Spodoptera frugiperda (JE Smith, 1797) (Lepidoptera: Noctuidae) was assessed by feeding larvae with leaves from six cassava genotypes (IAC-14, IAC-90, IAC-12, IAC-Caapora, Baianinha and MEcu 72). We performed the analysis of the chemical composition of these genotypes by quantification of total phenols and steroidal saponins. Analyzes by GC-MS were performed for the IAC-Caapora, Baianinha and MEcu 72 genotypes. A study was carried out to evaluate if S. frugiperda infestation induces changes in the concentration of the phytohormones, abscisic acid, salicylic acid and jasmonic acid, two molecules associated with the pathway of jasmonic acid (12-oxophitodienoic acid - OPDA and jasmonyl isoleucine) as well of cyanide (CN). Finally, analysis by LC-MS and quantification of hemagglutinating activity (AH) were performed in the six genotypes. The MEcu 72 genotype resulted in the worst nutritional indexes and, along with Baianinha, the worst reproductive indexes of S. frugiperda. The GC-MS analyzes resulted in the detection of 58 metabolites and 21 of these metabolites presented significant difference among the three evaluated genotypes. We detected myo-inositol-2-monophosphate, p-coumaric, chlorogenic and p-hydroxybenzoic acids, two forms of octadecadienoic acid and n-hexacosan in greater abundance in the MEcu 72 or Baianinha genotypes in relation to IAC-Caapora. MEcu 72 presents higher levels of constitutive phytohormones than the other genotypes. Herbivory caused changes in the levels of phytohormones and molecules associated with phytohormone pathways varing mainly according to the genotype tested, however, without a specific pattern. After herbivory, none of the evaluated genotypes altered the concentration of CN, which suggests that changes in herbivory-induced phytohormone concentrations are not related to CN biosynthesis pathway. By the LC-MS analyzes, the MEcu 72 genotype, a resistance standard for sap sucking insects, we found 10 exclusive metabolites and a metabolite with abundance 2 to 5 fold superior to the others and greater hemagglutinating activity. The possible roles of these molecules in the negative interferences caused on the development of insect pests are discussed.
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Cromatografia gasosa, Cromatografia líquida, Defesa química, Fitormônios, Metabolômica, Produtos naturais, Resistência induzida, Chemical defense, Gas chromatography, Induced resistance, Liquid chromatography, Metabolomics, Natural products, Phytohormones