title: Ozone affects ascorbate and glutathione biosynthesis as well as amino acid contents in three Euramerican poplar genotypes.
abstract: Ozone is an air pollutant that causes oxidative stress by generation of reactive oxygen species (ROS) within the leaf. The capacity to detoxify ROS and repair ROS-induced damage may contribute to ozone tolerance. Ascorbate and glutathione are known to be key players in detoxification. Ozone effects on their biosynthesis and on amino acid metabolism were investigated in three Euramerican poplar genotypes (Populus deltoides Bartr. × Populus nigra L.) differing in ozone sensitivity. Total ascorbate and glutathione contents were increased in response to ozone in all genotypes, with the most resistant genotype (Carpaccio) showing an increase of up to 70%. Reduced ascorbate (ASA) concentration at least doubled in the two most resistant genotypes (Carpaccio and Cima), whereas the most sensitive genotype (Robusta) seemed unable to regenerate ASA from oxidized ascorbate (DHA), leading to an increase of 80% of the oxidized form. Increased ascorbate (ASA + DHA) content correlated with the increase in gene expression in its biosynthetic pathway, especially the putative gene of GDP-l-galactose phosphorylase VTC2. Increased cysteine availability combined with increased expression of γ-glutamylcysteine synthetase (GSH1) and glutathione synthetase (GSH2) genes allows higher glutathione biosynthesis in response to ozone, particularly in Carpaccio. In addition, ozone caused a remobilization of amino acids with a decreased pool of total amino acids and an increase of Cys and putrescine, especially in Carpaccio. In addition, the expression of genes encoding threonine aldolase was strongly induced only in the most tolerant genotype, Carpaccio. Reduced ascorbate levels could partly explain the sensitivity to ozone for Robusta but not for Cima. Reduced ascorbate level alone is not sufficient to account for ozone tolerance in poplar, and it is necessary to consider several other factors including glutathione content.
authors.affiliation: INRA, UMR1137 EEF, F-54280 Champenoux, France.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Dumont
authors.forename: Sarita
authors.initials: S
authors.lastname: Keski-Saari
authors.forename: Markku
authors.initials: M
authors.lastname: Keinänen
authors.forename: David
authors.initials: D
authors.lastname: Cohen
authors.forename: Nathalie
authors.initials: N
authors.lastname: Ningre
authors.forename: Sari
authors.initials: S
authors.lastname: Kontunen-Soppela
authors.forename: Pierre
authors.initials: P
authors.lastname: Baldet
authors.forename: Yves
authors.initials: Y
authors.lastname: Gibon
authors.forename: Pierre
authors.initials: P
authors.lastname: Dizengremel
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Vaultier
authors.forename: Yves
authors.initials: Y
authors.lastname: Jolivet
authors.forename: Elina
authors.initials: E
authors.lastname: Oksanen
authors.forename: Didier
authors.initials: D
authors.lastname: Le Thiec
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D001205:Ascorbic Acid / Q000096:biosynthesis*; D018533:Biomass; D053898:Biosynthetic Pathways / Q000187:drug effects / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D005838:Genotype; D005978:Glutathione / Q000096:biosynthesis*; D010126:Ozone / Q000494:pharmacology*; D018515:Plant Leaves / Q000187:drug effects / Q000502:physiology; D032107:Populus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D010126:Ozone; D005978:Glutathione; D001205:Ascorbic Acid
keywords: Populus; air pollution; antioxidants; metabolism; oxidative stress