Plant stem cells are located in apical meristems at the growing tips of the shoot and the root. Signals from the neighboring organizing center within the shoot or quiescent center (QC) within the root maintain the stem cells in an undifferentiated state. The homeobox gene WUSCHEL-RELATED HOMEOBOX 5 (WOX5) is QC-specifically expressed and plays a central role in the control of the distal stem cells. However, the downstream factors of WOX5 and the molecular events triggered by WOX5 activity are not understood.Therefore, this project is intended to identify WOX5 primary target genes and to elucidate the roles of factors acting downstream of WOX5 in stem cell regulation. From pilot experiments, the first candidates for WOX5 target genes have been identified. I will perform a thorough transcriptome profiling of the QC, verify candidates by WOX5 protein -DNA binding studies in vivo, and by functional characterization. Furthermore, systems biology approach of the WOX5 downstream factors will be used for the construction of a regulatory network involved in stem cell niche signaling. Taken together, the proposed project will deepen the knowledge of how cell-cell communication in the stem cell niche functions.