POLTERGEIST and PLL1 are required for stem cell function with potential roles in cell asymmetry and auxin signaling.

Stem cell establishment and maintenance are essential for the largely post-embryonic developmental patterning that occurs in higher plants. Plant embryos establish two stem cell populations at the shoot and root meristems which then function to continuously generate shoot and root tissues, respectively. Research has uncovered entirely separate sets of regulators for the shoot and root stem cells, raising questions about the origin of the later-evolving root meristem and the relationship between the two meristems. We have recently demonstrated that the related Arabidopsis phosphatases POL and PLL1 are essential for both shoot and root stem cell maintenance and that they act in each population by promoting expression of related WOX transcription factors. Furthermore, pol pll1 mutant embryos exhibit defects in key asymmetric divisions in the early embryo. We hypothesize that the primary functions of POL and PLL1 are to establish and/or maintain stem cell polarity. Here we show additional data linking POL/PLL1 function to the proper polarization and localization of auxin signaling during embryogenesis.