Abstract
During the development of multicellular organisms, several distinct cell fates arise at defined positions. Cell type specific transcription factors play key roles in determining cell fates through the regulation of gene expression. ATML1, an Arabidopsis homeobox gene, is expressed in the outermost cell layer from the early stage of development. Many epidermis-specific genes including ATML1 contain an ATML1-binding site in their promoters, suggesting ATML1-mediated regulation of epidermal cell fate. However, it still remains unknown whether ATML1 is sufficient for the activation of these epidermis-specific genes. To further assess the role of ATML1 in epidermis-specific gene expression, we examined the effect of overexpression of ATML1 in the postembryonic development. Constitutive expression of ATML1 fused with a transcriptional repressor sequence decreased epidermis-specific gene expression and affected epidermal cell morphology. Conversely, constitutive expression of ATML1 was able to activate epidermis-specific genes in the inner cells of the seedling. These results suggested that ATML1 acts on the promoters of epidermis-specific genes and positively regulate their expressions.
