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.
Abe
Hiroshi
H
Biological Resources Division, Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan.
Urao
Takeshi
T
Ito
Takuya
T
Seki
Motoaki
M
Shinozaki
Kazuo
K
Yamaguchi-Shinozaki
Kazuko
K
D000040:Abscisic Acid / Q000494:pharmacology*; D000222:Adaptation, Physiological / Q000502:physiology; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D015152:Blotting, Northern; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D018525:Germination; D018257:Helix-Loop-Helix Motifs / Q000235:genetics; D008353:Mannitol / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D009997:Osmotic Pressure / Q000187:drug effects; D010802:Phylogeny; D030821:Plants, Genetically Modified; D012639:Seeds / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism
D029681:Arabidopsis Proteins; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D018076:DNA, Complementary; C104175:MYB2 protein, Arabidopsis; C473611:MYC2 protein, Arabidopsis; C473612:MYC3 protein, Arabidopsis; C473613:MYC4 protein, Arabidopsis; C080922:RD22 protein, Arabidopsis; D015534:Trans-Activators; D008353:Mannitol; D000040:Abscisic Acid