title: Ascorbate oxidase: the unexpected involvement of a 'wasteful enzyme' in the symbioses with nitrogen-fixing bacteria and arbuscular mycorrhizal fungi.
abstract: Ascorbate oxidase (AO, EC 1.10.3.3) catalyzes the oxidation of ascorbate (AsA) to yield water. AO over-expressing plants are prone to ozone and salt stresses, whereas lower expression apparently confers resistance to unfavorable environmental conditions. Previous studies have suggested a role for AO as a regulator of oxygen content in photosynthetic tissues. For the first time we show here that the expression of a Lotus japonicus AO gene is induced in the symbiotic interaction with both nitrogen-fixing bacteria and arbuscular mycorrhizal (AM) fungi. In this framework, high AO expression is viewed as a possible strategy to down-regulate oxygen diffusion in root nodules, and a component of AM symbiosis. A general model of AO function in plants is discussed.
authors.affiliation: Plant Protection Institute, National Research Council, Turin, Italy.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Balestrini
authors.forename: Thomas
authors.initials: T
authors.lastname: Ott
authors.forename: Mike
authors.initials: M
authors.lastname: Güther
authors.forename: Paola
authors.initials: P
authors.lastname: Bonfante
authors.forename: Michael K
authors.initials: MK
authors.lastname: Udvardi
authors.forename: Mario C
authors.initials: MC
authors.lastname: De Tullio
mesh_terms: D001204:Ascorbate Oxidase / Q000235:genetics* / Q000378:metabolism; D001205:Ascorbic Acid / Q000235:genetics; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D055137:Glomeromycota / Q000502:physiology*; D000070116:Lotus / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D059128:Mesorhizobium / Q000502:physiology*; D008954:Models, Biological; D038821:Mycorrhizae / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism; D009586:Nitrogen Fixation; D010100:Oxygen / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D053204:Root Nodules, Plant / Q000235:genetics / Q000382:microbiology / Q000502:physiology; D015398:Signal Transduction; D013559:Symbiosis / Q000502:physiology*
chemical_list: D001204:Ascorbate Oxidase; D009584:Nitrogen; D001205:Ascorbic Acid; D010100:Oxygen