title: The effect of ascorbic acid and dehydroascorbic acid on the root gravitropic response in Arabidopsis thaliana.
abstract: The effects of ascorbic acid (AA) and dehydroascorbic acid (DHA), one of products of the disproportionation of monodehydroascorbate (MDHA) by AA oxidase (AAO, EC 1.10.3.3), on the gravitropic curvature of Arabidopsis roots were characterized by biochemical and genetic approaches. Exogenously applied AA and DHA both stimulated root gravitropic responses in a concentration-dependent fashion. AA also changed the Indole-3-acetic acid (IAA) distribution in the roots after gravistimulation. In an effort to determine the relationship between AA and DHA in the gravitropic response, changes in the amount of reduced AA were evaluated in Arabidopsis under a variety of conditions. The expression level of an AAO gene (AAO1) was increased upon gravistimulation. Brassinolide (BL), indole-3-acetic acid (IAA), and AA also increased the transcript levels of this gene. Root elongation and the gravitropic response were both suppressed in the AA biosynthesis mutant, vtc1, which has a greatly reduced level of total AA. Furthermore, the line of AAO double mutants (aao1-1 X aao3-1, 41-21) showed a reduced gravitropic response and reduced root elongation. Taken together, the results of this study imply that both AA and DHA help to determine the redox environment for the root gravitropic response, but DHA, rather than AA, is a major player in the regulation of the gravitropic response mediated by AA in the roots of Arabidopsis thaliana.
authors.affiliation: Department of Life Science, Chung-Ang University, Seoul 156-756, Republic of Korea.
authors.forename: Yew
authors.initials: Y
authors.lastname: Lee
authors.forename: Chan Ho
authors.initials: CH
authors.lastname: Park
authors.forename: A
authors.initials: A
authors.lastname: Ram Kim
authors.forename: Soo Chul
authors.initials: SC
authors.lastname: Chang
authors.forename: Soo-Hwan
authors.initials: SH
authors.lastname: Kim
authors.forename: Woo Sung
authors.initials: WS
authors.lastname: Lee
authors.forename: Seong-Ki
authors.initials: SK
authors.lastname: Kim
mesh_terms: D042931:Aldehyde Oxidase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D060406:Brassinosteroids / Q000378:metabolism; D003683:Dehydroascorbic Acid / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant; D018522:Gravitropism / Q000502:physiology*; D007210:Indoleacetic Acids / Q000378:metabolism; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology*; D013260:Steroids, Heterocyclic / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids; D007210:Indoleacetic Acids; D013260:Steroids, Heterocyclic; C000820:semidehydroascorbic acid; C030737:indoleacetic acid; C467964:AAO1 protein, Arabidopsis; D042931:Aldehyde Oxidase; D009713:Nucleotidyltransferases; C026917:mannose 1-phosphate guanylyltransferase; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid; C023623:brassinolide