Epidermis-specific gene expression in Pachyphytum

Transcripts of exclusively epidermis-specific expression were obtained by differential screening of a cDNA library prepared from isolated epidermis tissue of a succulent plant, Pachyphytum. Six transcripts were selected and characterized by RNA gel blot hybridization. Five cDNAs represented abundant mRNAs found exclusively in the epidermis. In situ hybridizations with three of these transcripts further substantiated their epidermal location. While two transcripts were present in all cells of the epidermis, one transcript was enriched in subsidiary cells of the stomatal complexes. All of the transcripts were highly expressed in the protoderm of the shoot apical meristem. DNA sequence determination indicated that the mRNAs identified represent novel sequences, encoding yet unknown plant functions. These transcripts, their control elements, and their encoded functions should help to advance our understanding of epidermal cell determination and differentiation.