9630716 Irish The dicot flower generally consists of four whorls of floral organs, which arise through the coordinated proliferation of cells in each of the three cell layers of the floral meristem. Cell-cell interactions are important for the development of this floral pattern. These intercellular signaling events potentially include interwhorl, interorgan, and interlayer interactions. This project will investigate the extent to which each of these possible signaling mechanisms participates in establishing the floral pattern. Previous work has shown that expression of the DTA gene in the petal and stamen organ primordia results in ablation of petals and stamens. Grafing experiments, in which Nicotiana plants containing the DTA gene construct are grafted with wild type plants, will be used to examine the effects of ablating only part of the floral organ primordia. The resulting chimeric plants can be used to assess the degree to which remaining tissues can regenerate part or all of the missing patern elements. The results of these experiments will help to define the extent to which different signaling processes play in the specification of the differentiated floral pattern. In addition, the role of the floral homeotic APETALA3 (AP3) gene in cell-cell interactions in the development of the Arabidopsis flower will be defined. Using the heterologous Ac/Ds transposable element system, it will be possible to generate Arabidopsis plants that are mosaics of wild type AP3 and mutant ap3 tissues. These plants will be used to assess the role of the AP3 gene product in intercellular communication. Defining the parameters of where intercellular signals act, in combination with the analyses of the roles of individual gene products in these signaling processes, will lead to a more complete understanding of how meristematic cells coordinate their development to form the differentiated flower.
