title: Unraveling the role of fermentation in the mode of action of acetolactate synthase inhibitors by metabolic profiling.
abstract: Herbicides that inhibit branched chain amino acid biosynthesis induce aerobic fermentation. The role of fermentation in the mode of action of these herbicides is not known, nor is the importance of this physiological response in the growth inhibition and the lethality caused by them. Metabolic profiling was used to compare the effects of the herbicide imazethapyr (IM) on pea plants with two other treatments that also induce fermentation: hypoxia and the exogenous supply pyruvate for seven days. While hypoxic roots did not show internal anoxia, feeding pyruvate or applying IM to the roots led to internal anoxia, probably related to the respiratory burst detected. The three treatments induced ethanol fermentation, but fermentation induced following herbicide treatment was earlier than that following pyruvate supply and was not associated with a decrease in the energy status. No striking changes were detected in the metabolic profiling of hypoxic roots, indicating that metabolism was only slightly impaired. Feeding pyruvate resulted in marked succinate accumulation and a general amino acid accumulation. IM-treated roots showed a general accumulation of glycolytic metabolites upstream of pyruvate, a decrease in some TCA intermediates and an increase in the free amino acid pool sizes. All treatments caused GABA and putrescine accumulation. Our results indicate that IM supply impairs carbon/nitrogen metabolism and this impaired metabolism is likely to be related to the growth arrest detected. As growth is arrested, carbohydrates and glycolytic intermediates accumulate and energy becomes more available.
authors.affiliation: Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus Arrosadia, E-31006 Pamplona, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Zabalza
authors.forename: Luis
authors.initials: L
authors.lastname: Orcaray
authors.forename: María
authors.initials: M
authors.lastname: Igal
authors.forename: Nicolas
authors.initials: N
authors.lastname: Schauer
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.forename: Peter
authors.initials: P
authors.lastname: Geigenberger
authors.forename: Joost T
authors.initials: JT
authors.lastname: van Dongen
authors.forename: Mercedes
authors.initials: M
authors.lastname: Royuela
mesh_terms: D000095:Acetolactate Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism; D000597:Amino Acids, Branched-Chain / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D015687:Cell Hypoxia / Q000502:physiology; D005285:Fermentation / Q000187:drug effects* / Q000502:physiology; D008401:Gas Chromatography-Mass Spectrometry; D006540:Herbicides / Q000494:pharmacology*; D009539:Nicotinic Acids / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis / Q000378:metabolism*; D018532:Pisum sativum / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism; D011700:Putrescine / Q000378:metabolism; D019289:Pyruvic Acid / Q000494:pharmacology; D013997:Time Factors; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D000596:Amino Acids; D000597:Amino Acids, Branched-Chain; D006540:Herbicides; D009539:Nicotinic Acids; D005680:gamma-Aminobutyric Acid; C093630:imazethapyr; D019289:Pyruvic Acid; D000095:Acetolactate Synthase; D010100:Oxygen; D011700:Putrescine