The DDF1 transcriptional activator upregulates expression of a gibberellin-deactivating gene, GA2ox7, under high-salinity stress in Arabidopsis

Plant J. 2008 Nov;56(4):613-26. doi: 10.1111/j.1365-313X.2008.03627.x. Epub 2008 Sep 19.


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.

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis / metabolism
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • DNA, Bacterial / genetics
  • Gene Expression Regulation, Plant
  • Genes, Plant
  • Gibberellins / metabolism*
  • Mixed Function Oxygenases / genetics
  • Mixed Function Oxygenases / metabolism*
  • Mutagenesis, Insertional
  • Mutation
  • Oligonucleotide Array Sequence Analysis
  • Phenotype
  • Plants, Genetically Modified / genetics
  • Plants, Genetically Modified / metabolism
  • Promoter Regions, Genetic
  • RNA, Plant / genetics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Salinity
  • Salt-Tolerant Plants
  • Stress, Physiological*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism


  • Arabidopsis Proteins
  • DDF1 protein, Arabidopsis
  • DNA, Bacterial
  • Gibberellins
  • RNA, Plant
  • T-DNA
  • Trans-Activators
  • Mixed Function Oxygenases
  • AtGA2ox7 protein, Arabidopsis