Time Course of Benoxacor Metabolism and Identification of Benoxacor Metabolites Isolated from Suspension-Cultured <i>Zea mays</i> Cells 1 h after Treatment

Miller, Keith; Irzyk, Gerard P.; Fuerst, E. Patrick; McFarland, Janis E.; Barringer, M.; Cruz, S.; Eberle, Wolfgang; Föry, Werner

doi:10.1021/jf950542d

Cited by 18 publications

(38 citation statements)

References 20 publications

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“…Using these reference benoxacor metabolites, extracts from the suspension cultures treated with the safener for 16 h were then analysed by HPLC-ESI-MS. No parent benoxacor was identified, demon- strating that the safener had been metabolised. While the glutathionylated conjugates of the safener could not be detected, the formylcarboxyamide metabolite which is formed as a consequence of S-glutathionylation (Miller et al, 1996b), was observed in benoxacor-treated cultures but not in the controls. This confirmed that benoxacor was being rapidly conjugated with glutathione in Arabidopsis as demonstrated in maize cell cultures (Miller et al, 1996a,b).…”

Section: Safening Of Arabidopsis Cell Cultures By Benoxacormentioning

confidence: 80%

“…Using the published data from these metabolism studies, reference benoxacor metabolites were synthesised and characterised by HPLC-MS. The most abundant products derived from this chemical conjugation (Miller et al, 1996b) . Using these reference benoxacor metabolites, extracts from the suspension cultures treated with the safener for 16 h were then analysed by HPLC-ESI-MS. No parent benoxacor was identified, demon- strating that the safener had been metabolised.…”

Section: Safening Of Arabidopsis Cell Cultures By Benoxacormentioning

confidence: 99%

“…In phase 2, herbicides or their phase 1 metabolites are conjugated with either glucose by the action of glucosyltransferases (GTs) (Loutre et al, 2003) or with the tripeptide glutathione as catalysed by the glutathione transferases (GSTs) (Edwards and Dixon, 2000). In phase 3, conjugates are then actively transported into the vacuole (Rea et al, 1998) prior to phase 4 metabolism consisting of incorporation into bound residues (Skidmore, 2000). By considering these tiers of metabolism as part of a concerted process we have evolved the concept of the 'xenome', defining it as 'the biosystem responsible for the detection, transport and 0939Ð5075/2005/0300Ð0307 $ 06.00 " 2005 Verlag der Zeitschrift für Naturforschung, Tübingen · http://www.znaturforsch.com · D detoxification of xenobiotics'.…”

Section: Introductionmentioning

confidence: 99%

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Differential Induction of Glutathione Transferases and Glucosyltransferases in Wheat, Maize and Arabidopsis thaliana by Herbicide Safeners

Edwards

Buono

Fordham

et al. 2005

Zeitschrift Für Naturforschung C

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By learning lessons from weed science we have adopted three approaches to make plants more effective in phytoremediation: 1. The application of functional genomics to identify key components involved in the detoxification of, or tolerance to, xenobiotics for use in subsequent genetic engineering/breeding programmes. 2. The rational metabolic engineering of plants through the use of forced evolution of protective enzymes, or alternatively transgenesis of detoxification pathways. 3. The use of chemical treatments which protect plants from herbicide injury. In this paper we examine the regulation of the xenome by herbicide safeners, which are chemicals widely used in crop protection due to their ability to enhance herbicide selectivity in cereals. We demonstrate that these chemicals act to enhance two major groups of phase 2 detoxification enzymes, notably the glutathione transferases and glucosyltransferases, in both cereals and the model plant Arabidopsis thaliana, with the safeners acting in a chemical-and species-specific manner. Our results demonstrate that by choosing the right combination of safener and plant it should be possible to enhance the tolerance of diverse plants to a wide range of xenobiotics including pollutants.

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Section: Safening Of Arabidopsis Cell Cultures By Benoxacormentioning

confidence: 80%

Section: Safening Of Arabidopsis Cell Cultures By Benoxacormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Differential Induction of Glutathione Transferases and Glucosyltransferases in Wheat, Maize and Arabidopsis thaliana by Herbicide Safeners

Edwards

Buono

Fordham

et al. 2005

Zeitschrift Für Naturforschung C

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“…Synthetic standards of the glutathione and cysteine conjugates of [ 14 C]dimethenamid (synthesis protocol described below) and parent [ 14 C]dimethenamid were spotted for reference. The plate was developed twice in the same dimension using a chloroform/methanol/formic acid/water solvent system (first 75: 25:4:2 and then 60:40:4:2 v/v/v/v) (Miller et al, 1996). The solvent front was allowed to migrate to the top of the plate during each run (20 cm).…”

Section: Chemicalsmentioning

confidence: 99%

Initial Metabolism of Dimethenamid in Safened and Unsafened Wheat Shoots

Riechers

Fuerst

Miller

1996

J. Agric. Food Chem.

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The metabolic fate of the chloroacetamide herbicide dimethenamid was examined in excised shoots of unsafened and safened wheat seedlings. Compared to unsafened controls, fluxofenim treatment increased the rate of metabolism of dimethenamid to water-soluble compounds. Thin layer chromatography revealed that similar dimethenamid metabolites were present in extracts from both safened and unsafened wheat shoots. However, three metabolites were more abundant in extracts from fluxofenim-treated wheat relative to unsafened wheat. Reversed-phase highperformance liquid chromatography and mass spectrometry were used to isolate and confirm the identity of dimethenamid metabolites extracted from safened wheat shoots 1 h after treatment with dimethenamid. In addition to the presence of the glutathione conjugate of dimethenamid, γ-glutamylcysteine and cysteinylglycine dipeptide conjugates, as well as a cysteine conjugate and an oxygenated glutathione conjugate of dimethenamid, were detected. On the basis of time course analysis of dimethenamid metabolites by thin layer chromatography and structural identification by mass spectrometry, it appears that from 5 to 100 min after treatment with dimethenamid metabolism occurs exclusively via the glutathione conjugation pathway in wheat. Thus, the protection conferred to wheat by fluxofenim treatment is most likely due to increased glutathionemediated detoxification of dimethenamid.

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“…To date, such multiple rounds of conjugation of xenobiotics have rarely been recorded. A notable example is the safener benoxacor, which undergoes two rounds of glutathionylation in maize suspension cultures (30,31).…”

Section: Discussionmentioning

confidence: 99%

Catabolism of Glutathione Conjugates in Arabidopsis thaliana

Brazier-Hicks¹,

Evans²,

Cunningham

et al. 2008

Journal of Biological Chemistry

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The safener fenclorim (4,6-dichloro-2-phenylpyrimidine) increases tolerance to chloroacetanilide herbicides in rice by enhancing the expression of detoxifying glutathione S-transferases (GSTs). Fenclorim also enhances GSTs in Arabidopsis thaliana, and while investigating the functional significance of this induction in suspension cultures, we determined that these enzymes glutathionylated the safener. The resulting S-(fenclorim)-glutathione conjugate was sequentially processed to S-(fenclorim)-␥-glutamyl-cysteine and S-(fenclorim)-cysteine (FC), the latter accumulating in both the cells and the medium. FC was then either catabolized to 4-chloro-6-(methylthio)-phenylpyrimidine (CMTP) or N-acylated with malonic acid. These cysteine derivatives had distinct fates, with the enzymes responsible for their formation being induced by fenclorim and FC. Fenclorim-N-malonylcysteine was formed from FC by the action of a malonyl-CoA-dependent N-malonyltransferase. A small proportion of the fenclorim-N-malonylcysteine then underwent decarboxylation to yield a putative S-fenclorim-Nacetylcysteine intermediate, which underwent a second round of GST-mediated S-glutathionylation and subsequent proteolytic processing. The formation of CMTP was catalyzed by the concerted action of a cysteine conjugate ␤-lyase and an S-methyltransferase, with the two activities being coordinately regulated. Although the fenclorim conjugates tested showed little GST-inducing activity in Arabidopsis, the formation of CMTP resulted in metabolic reactivation, with the product showing good enhancing activity. In addition, CMTP induced GSTs and herbicide-safening activity in rice. The bioactivated CMTP was in turn glutathione-conjugated and processed to a malonyl cysteine derivative. These results reveal the surprisingly complex set of competing catabolic reactions acting on xenobiotics entering the S-glutathionylation pathway in plants, which can result in both detoxification and bioactivation.

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Time Course of Benoxacor Metabolism and Identification of Benoxacor Metabolites Isolated from Suspension-Cultured Zea mays Cells 1 h after Treatment

Cited by 18 publications

References 20 publications

Differential Induction of Glutathione Transferases and Glucosyltransferases in Wheat, Maize and Arabidopsis thaliana by Herbicide Safeners

Differential Induction of Glutathione Transferases and Glucosyltransferases in Wheat, Maize and Arabidopsis thaliana by Herbicide Safeners

Initial Metabolism of Dimethenamid in Safened and Unsafened Wheat Shoots

Catabolism of Glutathione Conjugates in Arabidopsis thaliana

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