Tolerance and Accumulation of Shikimic Acid in Response to Glyphosate Applications in Glyphosate-Resistant and Nonglyphosate-Resistant Cotton (Gossypium hirsutum L.)

Abstract

Measurement of shikimic acid accumulation in response to glyphosate inhibition of 5-enolpyruvylshikimate-3-phosphate synthase is a rapid and accurate assay to quantify glyphosate-induced damage in sensitive plants. Two methods of assaying shikimic acid, a spectrophotometric and a high-performance liquid chromatography (HPLC) method, were compared for their accuracy of recovering known amounts of shikimic acid spiked into plant samples. The HPLC method recovered essentially 100% of shikimic acid as compared with only 73% using the spectrophotometric method. Relative sensitivity to glyphosate was measured in glyphosate-resistant (GR) and non-GR cotton leaves, fruiting branches, and squares (floral buds) by assaying shikimic acid. Accumulation of shikimic acid was not observed in any tissue, either GR or non-GR, at rates of 5 mM glyphosate or less applied to leaves. All tissues of non-GR plants accumulated shikimic acid in response to glyphosate treatment; however, only fruiting branches and squares of GR plants accumulated a slight amount of shikimic acid. In non-GR cotton, fruiting branches and squares accumulated 18 and 11 times, respectively, more shikimic acid per micromolar of translocated glyphosate than leaf tissue, suggesting increased sensitivity to glyphosate of reproductive tissue over vegetative tissue. GR cotton leaves treated with 80 mM of glyphosate accumulated 57 times less shikimic acid per micromolar of translocated glyphosate than non-GR cotton but only 12.4- and 4-fold less in fruiting branches and squares, respectively. The increased sensitivity of reproductive structures to glyphosate inhibition may be due to a higher demand for shikimate pathway products and may provide an explanation for reports of fruit abortion from glyphosate-treated GR cotton.

Microwave-assisted solvent extraction and analysis of shikimic acid from plant tissues

“…Singh & Shaner (1998) and Mueller et al (2003) reported recoveries higher than 80% of spiked shikimic acid in crude extracts of soybean, maize and horseweed. Recoveries of 100% of shikimic acid in spiked samples of cotton, and 85% to 104% in fortified wheat tissue were also reported by Pline et al (2002) and Anderson et al (2001), respectively.…”

“…This herbicide acts by inhibiting the enzyme 5 -e n o l p y r u v y l s h i k i m a t e -3 -p h o s p h a t e synthase (EPSPS), thereby causing rapid and high levels of shikimic acid to accumulate in affected plant tissues . Measurement of shikimic acid accumulation in response to glyphosate inhibition is a rapid and accurate way to quantify and predict glyphosate-induced damage in sensitive plants (Harring et al, 1998;Pline et al, 2002;Henry et al, 2007).…”

“…Methods for the determination of shikimic acid include high performance liquid chromatography (HPLC) with UV detection (Harring et al, 1998), GC-MS (Duke et al, 2008) and spectrophotometry (Pline et al, 2002). Current extraction procedures require long extraction times and the use of high amounts of reagents such as methanol, ethanol, acetone, HCl, and sulfuric acid (Harring et al, 1998;Anderson et al, 2001;Jaroszynska, 2003;Mueller et al, 2003;Li et al, 2007).…”

Alterações no metabolismo da cana-de-açúcar em função da aplicação de maturadores

“…Matallo et al (2009), trabalhando com glyphosate e concentração de ácido chiquímico em citros, observaram que as plantas que receberam aplicação de glyphosate mostraram sempre maiores concentrações de ácido chiquímico que as plantas testemunhas. Vá-rios pesquisadores (Singh & Shaner, 1998;Wang, 2001;Mueller et al, 2003) (Mueller et al, 2003;Koger et al, 2005), algodão (Pline et al, 2002), girassol, trigo e milheto (Henry et al, 2007), soja (Singh & Shaner 1998) e trigo (Bresnahan et al, 2003.…”

Avaliação do uso de glyphosate em soja geneticamente modificada e sua relação com o ácido chiquímico

“…Pline et al (2002) examinaram o acúmulo de ácido chiquímico em variedades de algodão tanto sensíveis como resistentes ao glyphosate e também constataram aumento na concentração de ácido chiquímico nas folhas de algodão transgênico, sendo esse aumento muito inferior ao conteúdo encontrado nos frutos. Segundo esses autores, provavelmente esse aumento pode ser devido a uma menor demanda dos produtos da via do ácido chiquímico nas folhas.…”