Dependence of Stem Cell Fate in Arabidopsis on a Feedback Loop Regulated by CLV3 Activity

The fate of stem cells in plant meristems is governed by directional signaling systems that are regulated by negative feedback. In Arabidopsis thaliana , the CLAVATA ( CLV ) genes encode the essential components of a negative, stem cell–restricting pathway. We used transgenic plants overexpressing CLV3 to show that meristem cell accumulation and fate depends directly on the level of CLV3 activity and that CLV3 signaling occurs exclusively through a CLV1/CLV2 receptor kinase complex. We also demonstrate that the CLV pathway acts by repressing the activity of the transcription factor WUSCHEL , an element of the positive, stem cell–promoting pathway.