title: Gomphrena claussenii, a novel metal-hypertolerant bioindicator species, sequesters cadmium, but not zinc, in vacuolar oxalate crystals.
abstract: Gomphrena claussenii is a recently described zinc (Zn)- and cadmium (Cd)-hypertolerant Amaranthaceae species displaying a metal bioindicator Zn/Cd accumulation response. We investigated the Zn and Cd distribution in stem and leaf tissues of G. claussenii at the cellular level, and determined metabolite profiles to investigate metabolite involvement in Zn and Cd sequestration. Gomphrena claussenii plants exposed to high Zn and Cd supply were analysed by scanning electron microscopy with energy-dispersive X-ray (SEM-EDX) and micro-proton-induced X-ray emission (micro-PIXE). In addition, gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) was used to determine metabolite profiles on high Zn and Cd exposure. Stem and leaf tissues of G. claussenii plants exposed to control and high Cd conditions showed the abundant presence of calcium oxalate (CaOx) crystals, but on high Zn exposure, their abundance was strongly reduced. Ca and Cd co-localized to the CaOx crystals in Cd-exposed plants. Citrate, malate and oxalate levels were all higher in shoot tissues of metal-exposed plants, with oxalate levels induced 2.6-fold on Zn exposure and 6.4-fold on Cd exposure. Sequestration of Cd in vacuolar CaOx crystals of G. claussenii is found to be a novel mechanism to deal with Cd accumulation and tolerance.
authors.affiliation: Laboratory of Genetics, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, the Netherlands.
authors.forename: Mina T
authors.initials: MT
authors.lastname: Villafort Carvalho
authors.affiliation: Department of Biology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, SI-1000, Ljubljana, Slovenia.
authors.forename: Paula
authors.initials: P
authors.lastname: Pongrac
authors.affiliation: Plant Research International, Business Unit Bioscience, Wageningen UR, PO Box 16, 6700 AA, Wageningen, the Netherlands.
authors.forename: Roland
authors.initials: R
authors.lastname: Mumm
authors.affiliation: Plant Research International, Business Unit Bioscience, Wageningen UR, PO Box 16, 6700 AA, Wageningen, the Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: van Arkel
authors.affiliation: Laboratory of Virology, Wageningen Electron Microscopy Centre, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, the Netherlands.
authors.forename: Adriaan
authors.initials: A
authors.lastname: van Aelst
authors.affiliation: Jožef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.
authors.forename: Luka
authors.initials: L
authors.lastname: Jeromel
authors.affiliation: Jožef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.
authors.forename: Primož
authors.initials: P
authors.lastname: Vavpetič
authors.affiliation: Jožef Stefan Institute, Jamova 39, SI-1000, Ljubljana, Slovenia.
authors.forename: Primož
authors.initials: P
authors.lastname: Pelicon
authors.affiliation: Laboratory of Genetics, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, the Netherlands.
authors.forename: Mark G M
authors.identifier: http://orcid.org/0000-0001-5257-0740
authors.initials: MG
authors.lastname: Aarts
mesh_terms: D027703:Amaranthaceae / Q000378:metabolism* / Q000648:ultrastructure; D002104:Cadmium / Q000378:metabolism*; D002129:Calcium Oxalate / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D013052:Spectrometry, X-Ray Emission; D015032:Zinc / Q000378:metabolism*
chemical_list: D002104:Cadmium; D002129:Calcium Oxalate; D015032:Zinc
keywords: Gomphrena claussenii; cadmium (Cd); calcium oxalate (CaOx) crystal; cellular distribution; zinc (Zn)