WUSCHEL: The essential regulator of the Arabidopsis shoot Apical Meristem

Plant longevity depends on reservoirs of slowly proliferating stem cells, where a reduced rate of division is essential for maintaining DNA integrity. Aboveground stem cells are localized in the central zone of the shoot meristems, whose size is controlled by the transcription factor WUS. This review focuses on the mechanism of WUS function and the regulation of its expression. WUS maintains the central zone's size by controlling the hormones such as cytokinins. It forms complexes with various transcription factors and can act as a repressor and an activator of gene transcription. Cytokinins define WUS spatial expression relative to the meristem surface, while EPFL signaling limits WUS radial expansion. CLV3 signaling modulates WUS expression levels within the boundaries set by cytokinin and EPFLs. A significant overlap of WUS and CLV3 expression in the L3 layer suggests that autocrine signaling by CLV3 may play a central role in regulating WUS expression.