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Arabidopsis AtMYC2 (bHLH) and AtMYB2 (MYB) function as transcriptional activators in abscisic acid signaling.

In Arabidopsis, the induction of a dehydration-responsive gene, rd22, is mediated by abscisic acid (ABA). We reported previously that MYC and MYB recognition sites in the rd22 promoter region function as cis-acting elements in the drought- and ABA-induced gene expression of rd22. bHLH- and MYB-related transcription factors, rd22BP1 (renamed AtMYC2) and AtMYB2, interact specifically with the MYC and MYB recognition sites, respectively, in vitro and activate the transcription of the beta-glucuronidase reporter gene driven by the MYC and MYB recognition sites in Arabidopsis leaf protoplasts. Here, we show that transgenic plants overexpressing AtMYC2 and/or AtMYB2 cDNAs have higher sensitivity to ABA. The ABA-induced gene expression of rd22 and AtADH1 was enhanced in these transgenic plants. Microarray analysis of the transgenic plants overexpressing both AtMYC2 and AtMYB2 cDNAs revealed that several ABA-inducible genes also are upregulated in the transgenic plants. By contrast, a Ds insertion mutant of the AtMYC2 gene was less sensitive to ABA and showed significantly decreased ABA-induced gene expression of rd22 and AtADH1. These results indicate that both AtMYC2 and AtMYB2 proteins function as transcriptional activators in ABA-inducible gene expression under drought stress in plants.

Pubmed ID: 12509522


  • Abe H
  • Urao T
  • Ito T
  • Seki M
  • Shinozaki K
  • Yamaguchi-Shinozaki K


The Plant cell

Publication Data

January 1, 2003

Associated Grants


Mesh Terms

  • Abscisic Acid
  • Adaptation, Physiological
  • Amino Acid Sequence
  • Arabidopsis
  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • Blotting, Northern
  • DNA, Complementary
  • Gene Expression Regulation, Plant
  • Germination
  • Helix-Loop-Helix Motifs
  • Mannitol
  • Molecular Sequence Data
  • Mutation
  • Oligonucleotide Array Sequence Analysis
  • Osmotic Pressure
  • Phylogeny
  • Plants, Genetically Modified
  • Seeds
  • Sequence Homology, Amino Acid
  • Signal Transduction
  • Trans-Activators