Investigating Promoter Function in Vivo and the Role of Transposons as Control Elements

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Most fundamental cellular processes are controlled at the level of transcription. The extensive knowledge that has been acquired over the past years on the in vivo properties of the trans-acting regulators is contrasted by how little is still known about the in vivo organization, evolution and function of cis-acting regulatory elements. Insertions of transposons have played a crucial role in the evolution of eukaryotic promoters, but the fundaments on how this has impacted gene expression is not known. Previous studies on the control of maize flavonoid biosynthesis have provided the PI with unique tools to investigate the structure and function of cis-acting regulatory elements in their normal in vivo environment. As a model to understand promoter function in vivo, the regulatory region of a structural gene of the pathway (A1) that has been extensively dissected in vitro, and that is a target of at least two well-defined regulatory systems, will be studied. The cis-acting regulatory sequences that are important for the regulation of A1 in vivo will be established, by determining the effect of mutations and deletions of these elements on the expression of A1 in planta, and by exploiting the natural A1 allelic diversity in the Zea. In at least two well-characterized cases, the regulation of A1 becomes under the control of different transposable elements, albeit in exactly opposite ways.The unique understanding of the regulation of A1 makes it ideal to interpret transposable element gene control systems by providing important insights into the molecular bases of epigenetic phenomena. The PI will investigate whether the transposon insertions override the normal regulation of A1, and also determine whether the transposons provide novel cis-regulatory elements. Finally, the PI will examine which components of the corresponding transposases participate in the novel regulatory patterns displayed by the A1 alleles containing the transposon insertions. Taken together, these studies should provide one of the most comprehensive in vivo studies done on the regulatory region of a plant gene. Because of the uniqueness of the genetic and molecular tools available, the findings derived from these studies could be fundamental to the general field of regulation of gene expression.