title: Antioxidative ability and membrane integrity in salt-induced responses of Casuarina glauca Sieber ex Spreng. in symbiosis with N2-fixing Frankia Thr or supplemented with mineral nitrogen.
abstract: The actinorhizal tree Casuarina glauca tolerates extreme environmental conditions, such as high salinity. This species is also able to establish a root-nodule symbiosis with N2-fixing bacteria of the genus Frankia. Recent studies have shown that C. glauca tolerance to high salt concentrations is innate and linked to photosynthetic adjustments. In this study we have examined the impact of increasing NaCl concentrations (200, 400 and 600mM) on membrane integrity as well as on the control of oxidative stress in branchlets of symbiotic (NOD+) and non-symbiotic (KNO3+) C. glauca. Membrane selectivity was maintained in both plant groups at 200mM NaCl, accompanied by an increase in the activity of antioxidative enzymes (superoxide dismutase, ascorbate peroxidase, glutathione reductase and catalase). Regarding cellular membrane lipid composition, linolenic acid (C18:3) showed a significant decline at 200mM NaCl in both NOD+ and KNO3+ plants. In addition, total fatty acids (TFA) and C18:2 also decreased in NOD+ plants at this salt concentration, resulting in malondialdehyde (MDA) production. Such initial impact at 200mM NaCl is probably due to the fact that NOD+ plants are subjected to a double stress, i.e., salinity and low nitrogen availability. At 400mM NaCl a strong reduction of TFA and C18:3 levels was observed in both plant groups. This was accompanied by a decrease in the unsaturation degree of membrane lipids in NOD+. However, in both NOD+ and KNO3+ lipid modifications were not reflected by membrane leakage at 200 or 400mM, suggesting acclimation mechanisms at the membrane level. The fact that membrane selectivity was impaired only at 600mM NaCl in both groups of plants points to a high tolerance of C. glauca to salt stress independently of the symbiotic relation with Frankia.
authors.affiliation: Unidade de Biotecnologia e Recursos Genéticos, Instituto Nacional de Investigação Agrária e Veterinária, I.P. (INIAV), Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal; GeoBioTec, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal.
authors.forename: Paula
authors.initials: P
authors.lastname: Scotti-Campos
authors.affiliation: Plant Stress & Biodiversity Group, LEAF-Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal; Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. República, Quinta do Marquês, 2780-157 Oeiras, Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Duro
authors.affiliation: Plant Stress & Biodiversity Group, LEAF-Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal; Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. República, Quinta do Marquês, 2780-157 Oeiras, Portugal.
authors.forename: Mário da
authors.initials: Md
authors.lastname: Costa
authors.affiliation: Unidade de Biotecnologia e Recursos Genéticos, Instituto Nacional de Investigação Agrária e Veterinária, I.P. (INIAV), Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal.
authors.forename: Isabel P
authors.initials: IP
authors.lastname: Pais
authors.affiliation: Plant Stress & Biodiversity Group, LEAF-Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Rodrigues
authors.affiliation: Plant Stress & Biodiversity Group, LEAF-Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal.
authors.forename: Paula
authors.initials: P
authors.lastname: Batista-Santos
authors.affiliation: Unidade de Biotecnologia e Recursos Genéticos, Instituto Nacional de Investigação Agrária e Veterinária, I.P. (INIAV), Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal.
authors.forename: José N
authors.initials: JN
authors.lastname: Semedo
authors.affiliation: GeoBioTec, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal; Plant Stress & Biodiversity Group, LEAF-Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal.
authors.forename: A Eduardo
authors.initials: AE
authors.lastname: Leitão
authors.affiliation: GeoBioTec, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal.
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Lidon
authors.affiliation: Department of Ecology, Environment and Plant Sciences, Stockholm University, 10691 Stockholm, Sweden.
authors.forename: Katharina
authors.initials: K
authors.lastname: Pawlowski
authors.affiliation: GeoBioTec, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal; Plant Stress & Biodiversity Group, LEAF-Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal.
authors.forename: José C
authors.initials: JC
authors.lastname: Ramalho
authors.affiliation: GeoBioTec, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal; Plant Stress & Biodiversity Group, LEAF-Linking Landscape, Environment, Agriculture and Food, School of Agriculture, University of Lisbon, Quinta do Marquês, Av. República, 2784-505 Oeiras, Portugal; Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. República, Quinta do Marquês, 2780-157 Oeiras, Portugal. Electronic address: aribeiro@isa.ulisboa.pt.
authors.forename: Ana I
authors.initials: AI
authors.lastname: Ribeiro-Barros
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D040161:Frankia / Q000187:drug effects / Q000502:physiology*; D019684:Magnoliopsida / Q000187:drug effects* / Q000502:physiology; D009584:Nitrogen / Q000008:administration & dosage; D009586:Nitrogen Fixation; D018384:Oxidative Stress / Q000187:drug effects; D018517:Plant Roots / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology*; D013312:Stress, Physiological; D013559:Symbiosis / Q000187:drug effects*
chemical_list: D000975:Antioxidants; D012965:Sodium Chloride; D009584:Nitrogen
keywords: Actinorhizal plants; Antioxidative system; Lipoperoxidation; Membrane integrity; Salinity; Symbiosis