Identification of a cis-regulatory element for L1 layer-specific gene expression, which is targeted by an L1-specific homeodomain protein.
The Arabidopsis thaliana PROTODERMAL FACTOR1 (PDF1) gene encoding a putative extracellular proline-rich protein is exclusively expressed in the L1 layer of shoot apices and the protoderm of organ primordia. In order to identify essential cis-regulatory sequences required for the L1 layer-specific expression, a series of 5' deletions of the PDF1 promoter were fused to the beta-glucronidase (GUS) gene and introduced into Arabidopsis plants. Our analysis revealed that the minimum region necessary to confer L1-specific expression of PDF1 is confined within a 260-bp fragment upstream of the transcription start site. We identified an 8-bp motif in this region that is conserved between promoter regions of all the L1-specific genes so far cloned, and we designated it the L1 box. Electrophoretic mobility shift assays demonstrated that the L1-specific homeodomain protein ATML1 can bind to the L1 box sequence in vitro. The GUS expression in transgenic plants disappeared when a mutation that abolishes binding of ATML1 was introduced into the PDF1 l1 box sequence of the construct. These results suggest that the L1 box plays a crucial role in the regulation of PDF1 expression in L1 cells and that ATML1 could cooperate to drive L1-specific expression.
Abe
M
M
Division of Biological Sciences, Graduate School of Science, Hokkaido University, N10, W8, Sapporo, 060-0810, Japan.
Takahashi
T
T
Komeda
Y
Y
D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins; D001665:Binding Sites; D004252:DNA Mutational Analysis; D018744:DNA, Plant; D017930:Genes, Reporter; D005966:Glucuronidase / Q000235:genetics; D018398:Homeodomain Proteins / Q000378:metabolism*; D018519:Meristem / Q000235:genetics / Q000254:growth & development*; D010940:Plant Proteins / Q000235:genetics*; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012689:Sequence Homology, Nucleic Acid; D014018:Tissue Distribution
C103790:ATML1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018744:DNA, Plant; D018398:Homeodomain Proteins; C121819:PDF1 protein, Arabidopsis; D010940:Plant Proteins; D005966:Glucuronidase