Clonal analysis of epidermal patterning during maize leaf development

In plants, specialized epidermal cells are arranged in semiordered patterns . In grasses such as maize, stomata and other specialized cell types differ entiate in linear patterns within the leaf epidermis. A variety of mechanis ms have been proposed to direct patterns of epidermal cell differentiation. One class of models proposes that patterns of cellular differentiation dep end on the lineage relationships among epidermal cells. Another class of mo dels proposes that epidermal patterning depends on positional information r ather than lineage relationships. In the dicot epidermis, cell lineage is a n important factor in the patterning of stomata, but not trichomes. In this study, the role of cell lineage in the linear patterning of stomata and bu lliform cells in the maize leaf epidermis is investigated. Clones of epider mal cells in juvenile leaves were marked by excision of dSpm from gl15-m an d in adult leaves by excision of Ds2 from bz2-m. These clones were analyzed in relation to patterns of stomata and bulliform cells, testing specific p redictions of clonal origin hypotheses for the patterning of these cell typ es. We found that the great majority of clones analyzed failed to satisfy t hese predictions. Our results clearly show that lineage does not account fo r the linear patterning of stomata and bulliform cells, implying that posit ional information must direct the differentiation patterns of these cell ty pes in maize. (C) 1999 Academic Press.