A Quarter Century History of Gene Research.

The cloning of the gene, encoding an HD-ZIP class IV transcription factor, was first reported in 1996. Because mRNA was preferentially detected in the shoot epidermis, cis-regulatory sequences of have been used to drive gene expression in the outermost cells of the shoot apical meristem and leaves, even before the function of was understood. Later studies revealed that is required for developmental processes related to shoot epidermal specification and differentiation. Consistent with its central role in epidermal development, activity has been revealed to be restricted to the outermost cells via several regulatory mechanisms. In this review, we look back on the history of research and provide a perspective for future studies.