Negative autoregulation of the Arabidopsis homeobox gene ATHB-2.
The Arabidopsis homeobox gene ATHB-2 is tightly regulated by light signals, and is thought to direct morphological changes during shade avoidance responses. To understand how ATHB-2 mediates light signals in plant morphogenesis, we investigated its transcriptional network. We constructed a gene encoding a chimeric transcription factor (HD-Zip-2-V-G) that is expected to activate target genes of ATHB-2 in a glucocorticoid-dependent manner. In transgenic Arabidopsis plants expressing HD-Zip-2-V-G, glucocorticoid treatment activates the ATHB-2 gene itself, independent of de novo protein synthesis. An in vitro DNase I-footprinting experiment showed that recombinant ATHB-2 protein specifically bound to an ATHB-2 promoter region. These complementary results indicate that ATHB-2 recognizes its own promoter. Consistent with the fact that ATHB-2 itself has been shown to act as a repressor, expression of the endogenous ATHB-2 gene was repressed in transgenic plants overexpressing an ATHB-2 transgene. Moreover, target-gene analysis using the HD-Zip-2-V-G suggested that ATHB-2 recognizes other HD-Zip II subfamily genes. We conclude that ATHB-2 has a negative autoregulatory loop and may be involved in a complicated transcriptional network involving paralogous genes, as is the case with animal homeobox genes.
Ohgishi
M
M
Institute for Chemical Research, Kyoto University, Gokasho, Uji 611-0011, Japan.
Oka
A
A
Morelli
G
G
Ruberti
I
I
Aoyama
T
T
D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins; D001483:Base Sequence; D015152:Blotting, Northern; D018983:DNA Footprinting; D018744:DNA, Plant; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox; D018398:Homeodomain Proteins; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019076:Transgenes
D029681:Arabidopsis Proteins; D018744:DNA, Plant; D004268:DNA-Binding Proteins; C069386:HB-2 protein, Arabidopsis; D018398:Homeodomain Proteins; D010940:Plant Proteins; D011994:Recombinant Proteins