Role of SCHIZORIZA in asymmetric cell division, cell fate segregation and specification in Arabidopsis root development

Multicellular organisms develop their large variety of cell types from just one single cell, the zygote. Both plants and animals use asymmetric cell division to establish a multicellular body plan How different cell and tissue types are determined, how patterns are created and maintained, and which players are involved, are fundamental questions in developmental biology. Plants grow from their meristems, groups of dividing cells residing at foci of development. Within a meristem, stem cell niches are vital for maintaining the balance between stem cell self-renewal and differentiation. Stem cell divisions in Arabidopsis roots are asymmetric. Each root stem cell division gives rise to a new stem cell and a daughter cell that embarks on a trajectory towards differentiation, even though a limited number of cell divisions may still occur. Often the model plant Arabidopsis thaliana is used to illustrate the implementation of asymmetric cell division to create pattern and diversity. The heat shock transcription factor SCHIZORIZA (SCZ) is relevant for specification of root ground tissueand segregation of surrounding QC/columella and epidermal/lateral root cap fates (Mylona et al. 2002, ten Hove et al. 2010, Pernas, Ryan & Dolan 2010). This makes it an intriguing factor for studying asymmetric cell division and fate determination in Arabidopsis roots. The molecular foundation to SCZs mode of action is still unclear. This study aims to contribute a deeper understanding of asymmetric cell division and fate segregation. The SCZ target genes found endorse the view on the role of SCZ in cortex specification and outer tissue fate segregation. Three transcription factor genes, formerly unknown to pattern the rot meristem; ANTHOCYANINLESS2 (ANL2), TUBBY LIKE PROTEIN 8 (TLP8) and a C2H2 type Zinc Finger, ZN7571 are described. SCZ genetic interaction with the well characterized root patterning transcription factor genes SHORTROOT (SHR) and SCARECROW (SCR) is established. And it was shown that both SCZ and SHR/SCR are needed to establish the root stem cell niche during embryogenesis. Proteins that are able to physically interact with SCZ are identified.