Abstract
How cell fate is specified according to its position during plant embryogenesis is not well understood. Laser ablation studies and sector analyses suggested that the position of the cell rather than the lineage plays an important role in determining cell fate during plant development. However, it still remains unknown what factors provide the positional information. To elucidate the mechanism of position-dependent gene activation, we analyzed the regulation of ATML1 which was expressed in the outermost cell layer. Our expression studies suggested neither auxin signaling nor cell lineage was required for epidermis-specific expression of ATML1. Promoter deletion experiments revealed several cis-regulatory elements including ATML1-binding site contribute to the expression of ATML1, suggesting that several unknown factors as well as ATML1 itself regulate ATML1 expression. To identify factors that determine epidermis-specific expression of ATML1, we examined the effects of overexpression of several candidate genes that appeared to be involved in the regulation of ATML1 in the embryo. Possible roles of these genes in determining epidermis-specific gene expression will be discussed.
