title: Unraveling uranium induced oxidative stress related responses in Arabidopsis thaliana seedlings. Part II: responses in the leaves and general conclusions.
abstract: The cellular redox balance seems an important modulator under heavy metal stress. While for other heavy metals these processes are well studied, oxidative stress related responses are also known to be triggered under uranium stress but information remains limited. This study aimed to further unravel the mechanisms by which plants respond to uranium stress. Seventeen-day-old Arabidopsis thaliana seedlings, grown on a modified Hoagland solution under controlled conditions, were exposed to 0, 0.1, 1, 10 and 100 μM uranium for 1, 3 and 7 days. While in Part I of this study oxidative stress related responses in the roots were discussed, this second Part II discusses oxidative stress related responses in the leaves and general conclusions drawn from the results of the roots and the leaves will be presented. As several responses were already visible following 1 day exposure, when uranium concentrations in the leaves were negligible, a root-to-shoot signaling system was suggested in which plastids could be important sensing sites. While lipid peroxidation, based on the amount of thiobarbituric acid reactive compounds, was observed after exposure to 100 μM uranium, affecting membrane structure and function, a transient concentration dependent response pattern was visible for lipoxygenase initiated lipid peroxidation. This transient character of uranium stress responses in leaves was emphasized by results of lipoxygenase (LOX2) and antioxidative enzyme transcript levels, enzyme capacities and glutathione concentrations both in time as with concentration. The ascorbate redox balance seemed an important modulator of uranium stress responses in the leaves as in addition to the previous transient responses, the total ascorbate concentration and ascorbate/dehydroascorbate redox balance increased in a concentration and time dependent manner. This could represent either a slow transient response or a stable increase with regard to plant acclimation to uranium stress.
authors.affiliation: Belgian Nuclear Research Center (SCK•CEN), Biosphere Impact Studies, Boeretang 200, 2400 Mol, Belgium. nvanhoud@sckcen.be
authors.forename: Nathalie
authors.initials: N
authors.lastname: Vanhoudt
authors.forename: Ann
authors.initials: A
authors.lastname: Cuypers
authors.forename: Nele
authors.initials: N
authors.lastname: Horemans
authors.forename: Tony
authors.initials: T
authors.lastname: Remans
authors.forename: Kelly
authors.initials: K
authors.lastname: Opdenakker
authors.forename: Karen
authors.initials: K
authors.lastname: Smeets
authors.forename: Daniel Martinez
authors.initials: DM
authors.lastname: Bello
authors.forename: Michel
authors.initials: M
authors.lastname: Havaux
authors.forename: Jean
authors.initials: J
authors.lastname: Wannijn
authors.forename: May
authors.initials: M
authors.lastname: Van Hees
authors.forename: Jaco
authors.initials: J
authors.lastname: Vangronsveld
authors.forename: Hildegarde
authors.initials: H
authors.lastname: Vandenhove
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism; D015870:Gene Expression; D005978:Glutathione / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D015227:Lipid Peroxidation; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D011829:Radiation Dosage; D017382:Reactive Oxygen Species / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D014501:Uranium / Q000633:toxicity*
chemical_list: D000975:Antioxidants; D029681:Arabidopsis Proteins; D017382:Reactive Oxygen Species; D014501:Uranium; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D005978:Glutathione; D001205:Ascorbic Acid