Little is known about the cell and molecule processes that control flower development and reproduction in plants. Over the past several years genetic and molecular studies in the model plant system Arabidopsis thaliana have defined a hierarchy of genes that control flower development. The homeotic gene APETALA2 (AP2) has been shown to play a central role in regulating the production of the floral meristem and in controlling floral organ identity. However, the molecular function of AP2 is not known. Recently, we cloned the AP2 gene and showed that it encodes a novel protein distinguished by the AP2-domain, a 68 amino acid repeated motif that is essential for AP2 activity. Currently our research efforts are focused on understanding the function of AP2 in the plant cell. In addition, we recently made significant progress towards characterizing a newly discovered relationship between the plant growth regulator gibberellic acid and the mutant phenotypes of the Arabidopsis floral homeotic mutants apetala2, apetala1, leafy and agamous. During the next four years we plan to address the following questions: 1) What is the molecular function of AP2 and AP2-like proteins in the plant cell? 2) What are the cofactors, target genes, and regulators of AP2 that together determine floral organ identity? 3) What is the relationship between gibberellic acid and the regulation of floral homeotic gene expression in Arabidopsis? Any of these questions would make a good thesis project for an MBRS graduate student thesis. Several more defined genetic and molecular projects will be given to undergraduate students, e.g., the cloning and isolation of mutant ap2 genes, the RFLP mapping of cloned AP2-like genes, and the structural analysis of floral homeotic mutants using light and scanning electron microscopy.