Cellular interactions mediated by the homeotic PISTILLATA gene determine cell fate in the Arabidopsis flower.

Flowers develop from the coordinated division and differentiation of cells derived from the shoot apical meristem. By inducing chromosomal deletions in individual shoot apical meristem cells, we have generated Arabidopsis plants that are genetically mosaic for the homeotic PISTILLATA gene. Flowers bearing wild-type PISTILLATA epidermal tissue and mutant pistillata internal tissues are phenotypically normal. Based on this non-cell-autonomy, we suggest that PISTILLATA controls the production of a substance involved in cell-cell communication between the outer and inner tissue layers of the flower. These mosaic flowers were also used to assess the relative contributions of meristematic cells to the developing floral organs. These observations indicate that meristematic cells have discrete but somewhat variable contributions to the Arabidopsis flower. We have used these results to construct a fate map of the Arabidopsis floral primordium.