title: Tungsten disrupts root growth in Arabidopsis thaliana by PIN targeting.
abstract: Tungsten is a heavy metal with increasing concern over its environmental impact. In plants it is extensively used to deplete nitric oxide by inhibiting nitrate reductase, but its presumed toxicity as a heavy metal has been less explored. Accordingly, its effects on Arabidopsis thaliana primary root were assessed. The effects on root growth, mitotic cell percentage, nitric oxide and hydrogen peroxide levels, the cytoskeleton, cell ultrastructure, auxin and cytokinin activity, and auxin carrier distribution were investigated. It was found that tungsten reduced root growth, particularly by inhibiting cell expansion in the elongation zone, so that root hairs emerged closer to the root tip than in the control. Although extensive vacuolation was observed, even in meristematic cells, cell organelles were almost unaffected and microtubules were not depolymerized but reoriented. Tungsten affected auxin and cytokinin activity, as visualized by the DR5-GFP and TCS-GFP expressing lines, respectively. Cytokinin fluctuations were similar to those of the mitotic cell percentage. DR5-GFP signal appeared ectopically expressed, while the signals of PIN2-GFP and PIN3-GFP were diminished even after relatively short exposures. The observed effects were not reminiscent of those of any nitric oxide scavengers. Taken together, inhibition of root growth by tungsten might rather be related to a presumed interference with the basipetal flow of auxin, specifically affecting cell expansion in the elongation zone.
authors: Department of Botany, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece. Electronic address: iadamaki@bio.auth.gr.
authors: Ioannis-Dimosthenis S
authors: ID
authors: Adamakis
authors: Department of Botany, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece.
authors: Emmanuel
authors: E
authors: Panteris
authors: Department of Botany, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece.
authors: Eleftherios P
authors: EP
authors: Eleftheriou
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002470:Cell Survival; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017930:Genes, Reporter; D018522:Gravitropism; D006861:Hydrogen Peroxide / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D018519:Meristem / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D008938:Mitosis / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D011993:Recombinant Fusion Proteins; D015398:Signal Transduction / Q000187:drug effects; D014414:Tungsten / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; D006861:Hydrogen Peroxide; D026901:Membrane Transport Proteins; D009569:Nitric Oxide; D011993:Recombinant Fusion Proteins; D014414:Tungsten; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C449300:PIN3 protein, Arabidopsis
keywords: Actin filaments; Auxin; Cell vitality; Cytokinin; Nitric oxide