Two critical unanswered questions in developmental genetics are, how do homeotic selector genes lead to specification of specific organs?, and how do such regulators lead to appearance of specific cell types? The homeotic selector genes of the plant Arabidopsis thaliana, which function in the specification of organ identity during flower development, have been put under precise spatial and temporal control. They will be activated in plants with genotypes that dictate that the genes will be activating a single organ type, and the entire array of downstream activated and repressed genes will be determined using custom-designed microarrays. Chromatin immunoprecipitation and bioinformatic experiments will provide alternative methods for determining the active binding sites of these transcription factors. The result will be a detailed mechanistic description and causal model for each step and each gene involved in the initial stages of organ type specification, by each of the master regulatory genes engaged in spatial pattern formation in flowers. This in turn will provide fundamental information on a critical process in development that is shared by plants and animals, that when altered, leads to developmental defects. It will also give necessary information for beginning a complete gene circuit analysis of a complex developmental process. [unreadable] [unreadable]