January 23 2006
9:30 LSB 2320

Abstract:

Cell-to-cell communication is necessary for development and differentiation of multicellular organisms. In the Arabidopsis root the formation and differentiation of the ground tissue requires the activity of two related transcriptional regulators, SHORT-ROOT (SHR) and SCARECROW (SCR). SHR is an organizing signal regulating the division of a group of stem cells in the root apex through the activation of SCR. Both SHR and SCR are GRAS family proteins that are present in partially overlapping domains within the root. In the areas of the root where the expression of the SHR and SCR proteins does not overlap, these proteins show differences in subcellular localization and the ability to traffic between cells. Comparison of transcription with protein localization shows that SHR protein moves from the stele into the surrounding ground tissue. This is not true for SCR. The SHR protein is present both in the cytoplasm and nuclei of stele cells; whereas SCR is restricted to nuclei. As a way of determining what sequences within SHR and SCR are responsible for these differences, we have performed structure/function analysis of both the SHR and SCR proteins. We have identified multiple regions within SHR that are required for proper subcellular localization and movement of the protein. Significantly, addition of these domains to SCR are able to affect subcellular localization and in some instances confer movement.