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 RIS Download
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