title: Reduced Silver Nanoparticle Phytotoxicity in Crambe abyssinica with Enhanced Glutathione Production by Overexpressing Bacterial γ-Glutamylcysteine Synthase.
abstract: Silver nanoparticles (Ag NPs) are widely used in consumer products, and their release has raised serious concerns about the risk of their exposure to the environment and to human health. However, biochemical mechanisms by which plants counteract NP toxicity are largely unknown. We have previously engineered Crambe abyssinica plants expressing the bacterial γ-glutamylecysteine synthase (γ-ECS) for enhancing glutathione (GSH) levels. In this study, we investigated if enhanced levels of GSH and its derivatives can protect plants from Ag NPs and AgNO3 (Ag(+) ions). Our results showed that transgenic lines, when exposed to Ag NPs and Ag(+) ions, were significantly more tolerant, attaining a 28%-46% higher biomass and 34-49% more chlorophyll content, as well as maintaining 35-46% higher transpiration rates as compared to those of wild type (WT) plants. Transgenic γ-ECS lines showed 2-6-fold Ag accumulation in shoot tissue and slightly lower or no difference in root tissue relative to levels in WT plants. The levels of malondialdehyde (MDA) in γ-ECS lines were also 27.3-32.5% lower than those in WT Crambe. These results indicate that GSH and related peptides protect plants from Ag nanotoxicity. To our knowledge, this is the first direct report of Ag NP detoxification by GSH in transgenic plants, and these results will be highly useful in developing strategies to counteract the phytotoxicty of metal-based nanoparticles in crop plants.
authors.affiliation: †Stockbridge School of Agriculture, University of Massachusetts, Amherst, Massachusetts 01003, United States.
authors.forename: Chuanxin
authors.initials: C
authors.lastname: Ma
authors.affiliation: †Stockbridge School of Agriculture, University of Massachusetts, Amherst, Massachusetts 01003, United States.
authors.forename: Sudesh
authors.initials: S
authors.lastname: Chhikara
authors.affiliation: ‡USDA Forest Service, NRS, 271 Mast Road, Durham, New Hampshire 03824, United States.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Minocha
authors.affiliation: ‡USDA Forest Service, NRS, 271 Mast Road, Durham, New Hampshire 03824, United States.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Long
authors.affiliation: §Department of Analytical Chemistry, The Connecticut Agricultural Experiment Station, New Haven, Connecticut 06504, United States.
authors.forename: Craig
authors.initials: C
authors.lastname: Musante
authors.affiliation: §Department of Analytical Chemistry, The Connecticut Agricultural Experiment Station, New Haven, Connecticut 06504, United States.
authors.forename: Jason C
authors.initials: JC
authors.lastname: White
authors.affiliation: †Stockbridge School of Agriculture, University of Massachusetts, Amherst, Massachusetts 01003, United States.
authors.forename: Baoshan
authors.initials: B
authors.lastname: Xing
authors.affiliation: †Stockbridge School of Agriculture, University of Massachusetts, Amherst, Massachusetts 01003, United States.
authors.forename: Om Parkash
authors.initials: OP
authors.lastname: Dhankher
mesh_terms: D018533:Biomass; D002734:Chlorophyll / Q000378:metabolism; D031218:Crambe Plant / Q000187:drug effects* / Q000254:growth & development; D003545:Cysteine / Q000378:metabolism; D004151:Dipeptides / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D005978:Glutathione / Q000378:metabolism*; D006801:Humans; D015227:Lipid Peroxidation / Q000187:drug effects; D053768:Metal Nanoparticles / Q000633:toxicity*; D054811:Phytochelatins / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018526:Plant Transpiration / Q000187:drug effects; D030821:Plants, Genetically Modified; D012834:Silver / Q000633:toxicity*
chemical_list: D004151:Dipeptides; D002734:Chlorophyll; D012834:Silver; D054811:Phytochelatins; D005978:Glutathione; D003545:Cysteine; C017341:gamma-glutamylcysteine