title: Suppressed expression of the apoplastic ascorbate oxidase gene increases salt tolerance in tobacco and Arabidopsis plants.
abstract: Transgenic tobacco plants expressing the ascorbate oxidase (AAO) gene in sense and antisense orientations, and an Arabidopsis mutant in which the T-DNA was inserted into a putative AAO gene, were used to examine the potential roles of AAO for salt-stress tolerance in plants. AAO activities in the transgenic tobacco plants expressing the gene in sense and antisense orientations were, respectively, about 16-fold and 0.2-fold of those in the wild type. Under normal growth conditions, no significant differences in phenotypes were observed, except for a delay in flowering time in the antisense plants. However, at high salinity, the percentage germination, photosynthetic activity, and seed yields were higher in antisense plants, with progressively lower levels in the wild type and the sense plants. The redox state of apoplastic ascorbate in sense plants was very low even under normal growth conditions. Upon salt stress, the redox state of symplastic and apoplastic ascorbate decreased among the three types of plants, but was lowest in the sense plants. The hydrogen peroxide contents in the symplastic and apoplastic spaces were higher in sense plants, progressively lower in the wild type, followed by the antisense plants. The Arabidopsis T-DNA inserted mutant exhibited very low ascorbate oxidase activity, and its phenotype was similar to that of antisense tobacco plants. These results suggest that the suppressed expression of apoplastic AAO under salt-stress conditions leads to a relatively low level of hydrogen peroxide accumulation and a high redox state of symplastic and apoplastic ascorbate which, in turn, permits a higher seed yield.
authors.affiliation: Graduate School of Environmental and Human Sciences, Meijo University, Nagoya, 468-8502, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Yamamoto
authors.forename: Md Nazmul H
authors.initials: MN
authors.lastname: Bhuiyan
authors.forename: Rungaroon
authors.initials: R
authors.lastname: Waditee
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Tanaka
authors.forename: Muneharu
authors.initials: M
authors.lastname: Esaka
authors.forename: Kazuko
authors.initials: K
authors.lastname: Oba
authors.forename: André T
authors.initials: AT
authors.lastname: Jagendorf
authors.forename: Teruhiro
authors.initials: T
authors.lastname: Takabe
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001204:Ascorbate Oxidase / Q000235:genetics / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism; D004269:DNA, Bacterial / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D006861:Hydrogen Peroxide; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism; D012639:Seeds / Q000502:physiology; D012965:Sodium Chloride / Q000494:pharmacology*; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D004269:DNA, Bacterial; C036483:T-DNA; D012965:Sodium Chloride; D006861:Hydrogen Peroxide; D001204:Ascorbate Oxidase; D001205:Ascorbic Acid