Integration of pluripotency pathways regulates stem cell maintenance in theArabidopsisshoot meristem

Abstract

In the shoot meristem, both WUSCHEL (WUS) and SHOOT MERISTEMLESS (STM), two transcription factors with overlapping spatiotemporal expression patterns, are essential for maintaining stem cells in an undifferentiated state. Despite their importance, it remains unclear how these two pathways are integrated to coordinate stem cell development. Here, we show that the WUS and STM pathways inArabidopsis thalianaconverge through direct interaction between the WUS and STM proteins. STM binds to the promoter ofCLAVATA3(CLV3) and enhances the binding of WUS to the same promoter through the WUS–STM interaction. Both the heterodimerization and simultaneous binding of WUS and STM at two sites on theCLV3promoter are required to regulateCLV3expression, which in turn maintains a constant number of stem cells. Furthermore, the expression ofSTMdepends on WUS, and this WUS-activatedSTMexpression enhances the WUS-mediated stem cell activity. Our data provide a framework for understanding how spatial expression patterns within the shoot meristem are translated into regulatory units of stem cell homeostasis.