title: Biochemical characterization of metabolism-based atrazine resistance in Amaranthus tuberculatus and identification of an expressed GST associated with resistance.
abstract: Rapid detoxification of atrazine in naturally tolerant crops such as maize (Zea mays) and grain sorghum (Sorghum bicolor) results from glutathione S-transferase (GST) activity. In previous research, two atrazine-resistant waterhemp (Amaranthus tuberculatus) populations from Illinois, U.S.A. (designated ACR and MCR), displayed rapid formation of atrazine-glutathione (GSH) conjugates, implicating elevated rates of metabolism as the resistance mechanism. Our main objective was to utilize protein purification combined with qualitative proteomics to investigate the hypothesis that enhanced atrazine detoxification, catalysed by distinct GSTs, confers resistance in ACR and MCR. Additionally, candidate AtuGST expression was analysed in an F2population segregating for atrazine resistance. ACR and MCR showed higher specific activities towards atrazine in partially purified ammonium sulphate and GSH affinity-purified fractions compared to an atrazine-sensitive population (WCS). One-dimensional electrophoresis of these fractions displayed an approximate 26-kDa band, typical of GST subunits. Several phi- and tau-class GSTs were identified by LC-MS/MS from each population, based on peptide similarity with GSTs from Arabidopsis. Elevated constitutive expression of one phi-class GST, named AtuGSTF2, correlated strongly with atrazine resistance in ACR and MCR and segregating F2population. These results indicate that AtuGSTF2 may be linked to a metabolic mechanism that confers atrazine resistance in ACR and MCR.
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Anton F
authors.initials: AF
authors.lastname: Evans
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Sarah R
authors.initials: SR
authors.lastname: O'Brien
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Ma
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Aaron G
authors.initials: AG
authors.lastname: Hager
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Chance W
authors.initials: CW
authors.lastname: Riggins
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Kris N
authors.initials: KN
authors.lastname: Lambert
authors.affiliation: Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA.
authors.forename: Dean E
authors.identifier: http://orcid.org/0000-0002-6081-5629
authors.initials: DE
authors.lastname: Riechers
mesh_terms: D027721:Amaranthus / Q000235:genetics / Q000378:metabolism*; D001280:Atrazine; D005982:Glutathione Transferase / Q000378:metabolism*; D053209:Herbicide Resistance / Q000235:genetics; D006540:Herbicides; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D006540:Herbicides; D010940:Plant Proteins; D005982:Glutathione Transferase; D001280:Atrazine
keywords: 
  Amaranthus tuberculatus
  ; detoxification; glutathione S-transferase; herbicide metabolism; oxidative stress; proteome; weed resistance