Chromatographic determination of shikimate for identification of conventional soybean and glyphosate resistant soybean / Determinação cromatográfica de shikimato para identificação de soja convencional e soja resistente ao glifosato

A sensitive and reliable process was established using high-performance liquid chromatography (HPLC) to distinguish conventional varieties of glyphosate-resistant genetically modified crops via shikimate detection in soybean (Glycine max L. Merril) seeds. Glyphosate has a well-defined mechanism of action. It is the only herbicide that specifically inhibits 5-enolpiruvilshikimate-3-phosphate synthase (EPSPS E.C. 2.5.1.19), which catalyzes the condensation of shikimate with phosphoenolpyruvate. This study is based on the concept that shikimate significantly accumulates in soybean plant tissues after EPSPS inhibition by glyphosate. In plants not subjected to glyphosate, shikimate is not easily detected because it quickly metabolizes into shikimate 3-phosphate and subsequently into 5-enolpiruvilshikimate 3-phosphate through the action of EPSPS. Conversely, in non-genetically modified plants subjected to glyphosate, shikimate metabolism is impaired, resulting in its accumulation. This metabolite can be detected in extremely low quantities (in the microgram range), through HPLC. In this study, six different contrasts were analyzed, each being formed by a transgenic cultivation and its parental strain, subject or not subject to the treatment of soaking with a 0.6% glyphosate solution. Chromatographic analyses indicated shikimate accumulation only in conventional cultivars with seeds previously soaked in a 0.6% glyphosate solution. Thus, this shikimate detection method can be used as a rapid and accurate means to distinguish soybeans with glyphosate-resistant qualities.

Este estudo estabelece um processo, sensível e confiável, com aplicação de cromatografia líquida de alta eficiência (HPLC) para distinguir variedades de soja convencionais de geneticamente modificadas, resistentes ao glifosato, por detecção de chiquimato nas sementes. O mecanismo de ação doglifosato é bem definido. É o único herbicida que inibe especificamente a enzima 5-enolpiruvilchiquimato-3-fosfato sintase (EPSPS, E.C. 2.5.1.19), que catalisa a condensação do chiquimato com fosfoenolpiruvato. O trabalho está baseado na concepção do chiquimato se acumular significativamente nos tecidos vegetais de soja convencional, após a inibição da EPSP sintase pelo glifosato. Em plantas não submetidas ao glifosato, o chiquimato não é facilmente detectado, pois rapidamente é metabolizado a chiquimato 3-fosfato e, a seguir, em 5-enolpiruvilchiquimato 3-fosfato, pela ação da EPSPS. Por outro lado, em plantas não geneticamente modificadas submetidas ao glifosato, a metabolização do chiquimato é prejudicada, resultando em seu acúmulo. Este metabólito pode ser detectado em quantidades extremamente baixas (na faixa de µg), por HPLC. Neste trabalho foram analisados seis contrastes diferentes, sendo cada contraste formado por uma cultivar transgênica e sua respectiva cultivar parental convencional, submetidas ou não a embebição com solução de glifosato 0,6%. As análises cromatográficas indicaram o acúmulo de chiquimato apenas em cultivares convencionais, nas quais as sementes foram previamente embebidas em solução de glifosato 0,6%. Os resultados demonstraram que adetecção de chiquimato pode ser utilizada como um método rápido e preciso na diferenciação de soja resistente ao glifosato de soja convencional.

Naringenin inhibits the growth and stimulates the lignification of soybean root

The flavanone naringenin, an intermediate in flavonoid biosynthesis, was tested for its effect on root growth, phenylalanine ammonia-lyase (PAL) and peroxidase (POD) activities, as well as phenolic compounds and lignin contents in soybean (Glycine max L. Merrill) seedlings. Three-day-old seedlings were cultivated in half-strength Hoagland nutrient solution (pH 6.0), with or without 0.1 to 0.4 mM naringenin in a growth chamber (25°C, 12-h photoperiod, irradiance of 280 µmol m-2 s-1) for 24 h. Inhibitory effects on root growth (length, weight, cell viability), PAL and soluble POD activities were detected after naringenin treatments. These effects were associated with stimulatory activity of the cell wall-bound POD followed by an increase in the lignin contents, suggesting that naringenin-induced inhibition in soybean roots could be due to the lignification process.

Os efeitos de naringenina, um intermediário da biossíntese de flavonóides, foram avaliados sobre o crescimento das raízes, as atividades da fenilalanina amônia liase (PAL) e peroxidases, bem como sobre os teores de compostos fenólicos e de lignina em plântulas de soja (Glycine max L. Merrill). Plântulas de três dias foram cultivadas em solução nutritiva de Hoagland, meia-força (pH 6,0), contendo ou não, naringenina 0,1 a 0,4 mM, em uma câmara de germinação (25°C, fotoperíodo de 12 h, 280 µmol m-2 s-1) durante 24 h. Efeitos inibitórios no crescimento das raízes (comprimento, massa e viabilidade celular) e nas atividades da PAL e POD solúvel foram constatados após os tratamentos com naringenina. Estes efeitos foram associados com atividade estimulatória da POD ligada à parede celular, seguido por aumento nos teores de lignina, sugerindo que a inibição do crescimento das raízes pode ser devido ao processo de lignificação.

Peroxidase and lipid peroxidation of soybean roots in response to p-coumaric and p-hydroxybenzoic acids

The scope of the present study was to investigate how the p-coumaric (p-CA) and p-hydroxybenzoic (p-HD) acids affect the peroxidase (POD, EC 1.11.1.7) activity, the lipid peroxidation (LP) and the root growth of soybean (Glycine max (L.) Merr.). Three-day-old seedlings were cultivated in nutrient solution containing p-CA or p-HD (0.1 to 1 mM) for 48 h. After uptake, both compounds (at 0.5 and 1 mM) decreased root length (RL), fresh weight (FW) and dry weight (DW) while increased soluble POD activity, cell wall (CW)-bound POD activity (with 1 mM p-CA and 0.5 mM p-HD) and LP

Peroxidase and phenylalanine ammonia-lyase activities, phenolic acid contents, and allelochemicals-inhibited root growth of soybean

The influence of the allelochemicals ferulic (FA) and vanillic (VA) acids on peroxidase (POD, EC 1.11.1.7) and phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) activities and their relationships with phenolic acid (PhAs) contents and root growth of soybean (Glycine max (L.) Merr.) were examined. Three-day-old seedlings were cultivated in nutrient solution containing FA or VA (0.1 to 1 mM) for 48 h. Both compounds (at 0.5 and 1 mM) decreased root length (RL), fresh weight (FW) and dry weight (DW) and increased PhAs contents. At 0.5 and 1 mM, FA increased soluble POD activity (18% and 47%, respectively) and cell wall (CW)-bound POD activity (61% and 34%), while VA increased soluble POD activity (33% and 17%) but did not affect CW-bound POD activity. At 1 mM, FA increased (82%) while VA reduced (32%) PAL activities. The results are discussed on the basis of the role of these compounds on phenylpropanoid metabolism and root growth and suggest that the effects caused on POD and PAL activities are some of the many mechanisms by which allelochemicals influence plant growth.