The Stem Cell Population of Arabidopsis Shoot Meristems Is Maintained by a Regulatory Loop between the CLAVATA and WUSCHEL Genes

The higher-plant shoot meristem is a dynamic structure whose maintenance depends on the coordination of two antagonistic processes, organ initiation and self-renewal of the stem cell population. In Arabidopsis shoot and floral meristems, the WUSCHEL ( WUS) gene is required for stem cell identity, whereas the CLAVATA1, 2, and 3 ( CLV) genes promote organ initiation. Our analysis of the interactions between these key regulators indicates that (1) the CLV genes repress WUS at the transcript level and that (2) WUS expression is sufficient to induce meristem cell identity and the expression of the stem cell marker CLV3. Our data suggest that the shoot meristem has properties of a self-regulatory system in which WUS/ CLV interactions establish a feedback loop between the stem cells and the underlying organizing center.