title: Glyphosate resistance in Ambrosia trifida: Part 2. Rapid response physiology and non-target-site resistance.
abstract: BACKGROUND
  The glyphosate-resistant rapid response (GR RR) resistance mechanism in Ambrosia trifida is not due to target-site resistance (TSR) mechanisms. This study explores the physiology of the rapid response and the possibility of reduced translocation and vacuolar sequestration as non-target-site resistance (NTSR) mechanisms.
  
  
  RESULTS
  GR RR leaf discs accumulated hydrogen peroxide within minutes of glyphosate exposure, but only in mature leaf tissue. The rapid response required energy either as light or exogenous sucrose. The combination of phenylalanine and tyrosine inhibited the rapid response in a dose-dependent manner. Reduced glyphosate translocation was observed in GR RR, but only when associated with tissue death caused by the rapid response. Nuclear magnetic resonance studies indicated that glyphosate enters the cytoplasm and reaches chloroplasts, and it is not moved into the vacuole of GR RR, GR non-rapid response or glyphosate-susceptible A. trifida.
  
  
  CONCLUSIONS
  The GR RR mechanism of resistance is not associated with vacuole sequestration of glyphosate, and the observed reduced translocation is likely a consequence of rapid tissue death. Rapid cell death was inhibited by exogenous application of aromatic amino acids phenylalanine and tyrosine. The mechanism by which these amino acids inhibit rapid cell death in the GR RR phenotype remains unknown, and it could involve glyphosate phytotoxicity or other agents generating reactive oxygen species. Implications of these findings are discussed. The GR RR mechanism is distinct from the currently described glyphosate TSR or NTSR mechanisms in other species. © 2017 Society of Chemical Industry.
authors.affiliation: Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA.|Department of Horticulture, Oregon State University, Corvallis, OR, USA.
authors.forename: Marcelo L
authors.identifier: http://orcid.org/0000-0001-8313-9195
authors.initials: ML
authors.lastname: Moretti
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, USA.|United States Department of Agriculture - Agricultural Research Service, San Joaquin Valley Agricultural Sciences Center, Parlier, CA, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Van Horn
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA.
authors.forename: Renae
authors.initials: R
authors.lastname: Robertson
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA.|Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA.
authors.forename: Kabelo
authors.initials: K
authors.lastname: Segobye
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Weller
authors.affiliation: Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA.
authors.forename: Bryan G
authors.initials: BG
authors.lastname: Young
authors.affiliation: Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN, USA.
authors.forename: William G
authors.initials: WG
authors.lastname: Johnson
authors.affiliation: Monsanto Company, St Louis, MO, USA.
authors.forename: R
authors.initials: R
authors.lastname: Douglas Sammons
authors.affiliation: Monsanto Company, St Louis, MO, USA.
authors.forename: Dafu
authors.initials: D
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Washington University, St Louis, MO, USA.
authors.forename: Xia
authors.initials: X
authors.lastname: Ge
authors.affiliation: Department of Chemistry, Washington University, St Louis, MO, USA.
authors.forename: André
authors.initials: A
authors.lastname: d' Avignon
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, USA.
authors.forename: Todd A
authors.identifier: http://orcid.org/0000-0003-1485-7665
authors.initials: TA
authors.lastname: Gaines
authors.affiliation: Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Westra
authors.affiliation: Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
authors.forename: Amanda C
authors.initials: AC
authors.lastname: Green
authors.affiliation: Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
authors.forename: Taylor
authors.initials: T
authors.lastname: Jeffery
authors.affiliation: Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
authors.forename: Mackenzie A
authors.initials: MA
authors.lastname: Lespérance
authors.affiliation: Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
authors.forename: François J
authors.initials: FJ
authors.lastname: Tardif
authors.affiliation: Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Sikkema
authors.affiliation: Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Christopher Hall
authors.affiliation: Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
authors.forename: Michael D
authors.initials: MD
authors.lastname: McLean
authors.affiliation: Monsanto Company, Guelph, ON, Canada.
authors.forename: Mark B
authors.initials: MB
authors.lastname: Lawton
authors.affiliation: Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN, USA.|Department of Plant Science and Landscape Architecture, University of Maryland, College Park, MD, USA.
authors.forename: Burkhard
authors.initials: B
authors.lastname: Schulz
mesh_terms: D031164:Ambrosia / Q000187:drug effects* / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D005998:Glycine / Q000031:analogs & derivatives* / Q000378:metabolism; D053209:Herbicide Resistance; D006540:Herbicides / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D057685:Plant Weeds / Q000187:drug effects* / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism; D000097797:Glyphosate
chemical_list: D005998:Glycine; D006540:Herbicides; D000097797:Glyphosate
keywords: Ambrosia trifida; giant ragweed; nuclear magnetic resonance; rapid response; sequestration; translocation