MOLECULAR CONTROL OF FLOWER DEVELOPMENT IN ARABIDOPSIS

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Research in my laboratory is focused on understanding the processes controlling flower development in the crucifer Arabidopsis thaliana. In Arabidopsis, mutations in the homeotic regulatory gene Apetala2 (Ap2) can cause the homeotic transformation of sepals to carpels and petals to stamens, as well as other dramatic changes in floral organ development. Clearly, the Apetala2 gene plays a central role in determining the identity of floral organ primordia and the regulation of plant reproduction. However, nothing is known about the function of this gene at the molecular level. Recently, my colleagues and I cloned the Ap2 gene from Arabidopsis by insertional mutagenesis. Analysis of the Ap2 nucleotide sequence has not provided any meaningful clues to this gene's function in the cell. Therefore, the experiments in this proposal are designed to generate new molecular and genetic insights into the structure of Apetala2, the temporal and spatial regulation of this gene during Arabidopsis development, and its interactions with other gene loci involved in the genetic control of flower development. First, to identify structurally and/or functionally important regions of the Ap2 gene we will compare the nucleotide sequence of wildtype Ap2 and its flanking DNA sequences with several chemically induced mutant alleles. In addition, we will determine whether several interesting motifs in the Ap2 amino acid sequence are critical for this gene's function by generating a set of new mutant alleles using in vitro site-directed mutagenesis in conjunction with the transformation of these mutant genes back into Arabidopsis. A second goal of our research is to understand how Ap2 interacts with other Arabidopsis gene loci involved in the regulation of floral organogenesis. To define the interactions and/or epistatic relationships between Ap2 and other known regulatory gene loci, we propose to look at the temporal and spatial regulation of Ap22 gene expression in mutant plants using in situ hybridization and immunolocalization procedures. Finally, to identify new genes that interact with Ap2 to determine the identity of floral organ primordia, we propose to screen mutagenized ap2 plants for modifiers of the homeotic phenotype -- dominant enhancer and suppressor mutants of ap2. This genetic screen should identify additional elements of the regulatory network controlling flower development including regulators, cofactors, as well as downstream target genes of ap2. Together, these studies should provide new insight into the molecular processes controlling plant pattern formation and reproduction.