A major unanswered question in developmental biology is how the final size of an animal or plant is determined. This study explores the roles of hormones in regulating organ size and stature in plants. Recent studies in the P.I.'s laboratory indicate that the plant hormones auxin and brassinosteroids (BRs) act in close proximity to regulate seedling growth. Using genetics, genomics, and physiological analyses, it was shown that the auxin and BR pathways are interconnected and this integration is likely to occur at the level of gene expression. This project will continue to explore the underlying molecular mechanism of this BR/auxin synergism and seek to identify new factors involved in growth regulation by BRs and auxin. These experiments will address the mechanism by which these hormones interact to regulate such diverse responses as changes in gene expression, cell expansion and division, and tissue differentiation. The long-term objective is to completely understand the signaling networks that regulate plant development in response to an ever-changing environment, and to relate this to strategies used in other organisms. An anticipated broader impact is a continuing commitment to post-graduate, graduate, and undergraduate education, as well as exposure of high school students to a research laboratory setting. Also, the computational analyses to be carried out allow access to publicly available datasets that are of general use to the molecular biology community, and we have made the information available through several recently implemented websites. Consequently, the analytical methods and the information generated by their implementation may be a valuable community resource.