Stem cell regulation in the shoot meristem.

A small group of pluripotent stem cells in the shoot meristem is the ultimate source for all aerial parts in higher plants: the shoot axis, side branches, leaves and flowers. The stem cells are maintained in an undifferentiated state by signals from an underlying cell group, the organizing center. Genetic and molecular analyses have shown that a feedback signaling loop between stem cells and the organizing center balances stem cell renewal versus differentiation, which allows the plant to maintain the organization of the shoot meristem despite a changing cellular context. Emerging common principles indicate that plant and animal stem cells are functionally equivalent.