title: The DDF1 transcriptional activator upregulates expression of a gibberellin-deactivating gene, GA2ox7, under high-salinity stress in Arabidopsis.
abstract: High-salinity stress affects plant growth and development. We have previously reported that overexpression of the salinity-responsive DWARF AND DELAYED FLOWERING 1 (DDF1) gene, encoding an AP2 transcription factor of the DREB1/CBF subfamily, causes dwarfism mainly by levels of reducing bioactive gibberellin (GA) in transgenic Arabidopsis. Here, we found that the GA 2-oxidase 7 gene (GA2ox7), which encodes a C20-GA deactivation enzyme, is strongly upregulated in DDF1-overexpressing transgenic plants. A loss-of-function mutation of GA2ox7 (ga2ox7-2) suppressed the dwarf phenotype of DDF1-overexpressing plants, indicating that their GA deficiency is due to overexpression of GA2ox7. Transient overexpression of DDF1 activated the promoter of GA2ox7 in Arabidopsis leaves. A gel shift assay showed that DDF1 binds DRE-like motifs (GCCGAC and ATCGAC) in the GA2ox7 promoter. In Arabidopsis under high-salinity stress, six GA2ox genes, including GA2ox7, were upregulated. Furthermore, the ga2ox7-2 mutant was less growth retarded than wild-type Col under high-salinity stress. These results demonstrate that, under salinity stress, Arabidopsis plants actively reduce endogenous GA levels via the induction of GA 2-oxidase, with the result that growth is repressed for stress adaptation.
authors.affiliation: Research Institute for Biological Sciences, 7549-1 Yoshikawa, Kibi-chuo, Okayama 716-1241, Japan. uhmagome@psc.riken.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Magome
authors.forename: Shinjiro
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hanada
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Kenji
authors.initials: K
authors.lastname: Oda
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005875:Gibberellins / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054712:Salinity; D055051:Salt-Tolerant Plants; D013312:Stress, Physiological; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C487098:DDF1 protein, Arabidopsis; D004269:DNA, Bacterial; D005875:Gibberellins; D018749:RNA, Plant; C036483:T-DNA; D015534:Trans-Activators; D006899:Mixed Function Oxygenases; C499575:AtGA2ox7 protein, Arabidopsis