The Protein Phosphatases POL and PLL1 are Signaling Intermediates for Multiple Pathways in Arabidopsis.

The development of plants from seedlings to mature adult organisms requires the precise maintenance of the stem cell populations at meristems. In Arabidopsis, the CLAVATA (CLV) pathway is vital for homeostatic regulation of stem cell populations at shoot and floral meristems. Two components of this pathway are the protein phosphatase type 2 C proteins, POLTERGEIST (POL) and PLL1, which positively regulate stem cell specification. Recent studies by our laboratory demonstrated that POL and PLL1 are vital not only for meristem regulation but also for other essential developmental processes including those regulating the formation of the central vasculature and the basal half of the embryo. These results suggest that POL and PLL1 are components of multiple pathways, not just the CLV pathway. Furthermore, considering the processes that are disrupted in the pol pll1 double mutants it is possible that POL and PLL1 are required for certain asymmetric cell divisions during development.