title: Allantoin Increases Cadmium Tolerance in Arabidopsis via Activation of Antioxidant Mechanisms.
abstract: Plants apply various molecular, physiological and morphological strategies in response to undesirable environmental conditions. One of the possible responses which may contribute to surviving stressful conditions is the accumulation of ureides. Ureides are recognized as important nitrogen-rich compounds involved in recycling nitrogen in plants to support growth and reproduction. Amongst them, allantoin not only serves as a transportable nitrogen-rich compound, but has also been suggested to protect plants from abiotic stresses via minimizing oxidative damage. This work focuses on the effect of cadmium (Cd) on ureide metabolism in Arabidopsis, in order to clarify the potential role of allantoin in plant tolerance to heavy metals. In response to Cd treatment, allantoin levels increase in Arabidopsis thaliana, ecotype Col-0, due to reduced allantoinase (ALN) gene expression and enzyme activity. This coincides with increases in uricase (UO) transcripts. UO and ALN encode the enzymes for the production and degradation of allantoin, respectively. ALN-negative aln-3 Arabidopsis mutants with elevated allantoin levels demonstrate resistance to soil-applied CdCl2, up to 1,500 μM. Although aln-3 mutants take up and store more Cd within their leaf tissue, they contain less damaging superoxide radicals. The protective mechanism of aln-3 mutants appears to involve enhancing the activity of antioxidant enzymes such as superoxide dismutase and ascorbate peroxidase.
authors.affiliation: Department of Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada.
authors.forename: Maryam
authors.initials: M
authors.lastname: Nourimand
authors.affiliation: Department of Biology, University of Saskatchewan, Saskatoon, SK, S7N 5E2, Canada chris.todd@usask.ca.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Todd
mesh_terms: D000481:Allantoin / Q000032:analysis / Q000378:metabolism*; D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism; D000975:Antioxidants / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D060387:Ascorbate Peroxidases / Q000378:metabolism; D002104:Cadmium / Q000633:toxicity*; D018506:Gene Expression Regulation, Plant; D019216:Metals, Heavy / Q000633:toxicity; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D012639:Seeds / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D013312:Stress, Physiological; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D014527:Uric Acid / Q000032:analysis / Q000378:metabolism
chemical_list: D000975:Antioxidants; D029681:Arabidopsis Proteins; D019216:Metals, Heavy; D017382:Reactive Oxygen Species; D002104:Cadmium; D013481:Superoxides; D014527:Uric Acid; D000481:Allantoin; D060387:Ascorbate Peroxidases; D013482:Superoxide Dismutase; D000581:Amidohydrolases; C019659:allantoinase; D009584:Nitrogen
keywords: Allantoin; Antioxidant enzymes; Arabidopsis thaliana; Cadmium; Reactive oxygen species; Ureides