Cloning and characterization of an L1 layer-specific gene in Arabidopsis thaliana

The shoot apical meristem unknown. In order to identify the genes that func tion in the SAM, we performed cDNA subtraction experiments between wild-typ e and terminal flower1 shoot apices. Here, we describe the cloning of a gen e designated PDF1 (PROTODERMAL FACTOR1). In situ hybridization revealed tha t the expression of PDF1 is exclusively limited to the L1 layer of vegetati ve, inflorescence and floral meristems and to the protoderm of organ primor dia. By contrast, P (SAM) of Arabidopsis thaliana constitutes the tunica of L1 and L2 and the corpus represented by L3 cells. Regulatory networks invo lved in establishing and maintaining this structure of shoot meristems rema in largelyDF1 shows no detectable level of expression in the epidermis of m ature organs. Specific expression of the PDF1 gene in protodermal cells is also observed during embryogenesis. The deduced amino acid sequence of PDF1 shares no significant homology with that of other known proteins but conta ins a putative signal peptide and novel proline-rich repeat motifs, suggest ing a cell-wall protein. Possible roles of the PDF1 gene in the SAM are dis cussed.