POLTERGEIST and POLTERGEIST - LIKE1 are essential for the maintenance of post-embryonic shoot and root apical meristems as revealed by a partial loss-of-function mutant allele of pll1 in Arabidopsis

Background POLTERGEIST ( POL ) and POL - LIKE1 ( PLL1 ) encoding related protein phosphatase 2Cs are essential for the establishment of both shoot and root meristems during embryogenesis. As the strong pol pll1 are seedling-lethal due to the lack of hypocotyl vasculature, the roles of POL / PLL1 for the post-embryonic development is difficult to be assessed. Objective To prepare a weak pol pll1 double mutant that are able to produce post-embryonic organs. Methods Several T-DNA insertion mutants of pll1 were crossed to pol - 6 for the preparation of weak pol pll1 . To understand the epistatic interactions between POL / PLL1 and CLAVATAs , the phenotypes of clv s pol pll1 were assessed and the expression patterns of stem cell markers were examined in pol pll1 . POLpro:PLL1 - GFP expression was examined during the embryogenesis with confocal microscopy. Results We isolated a pll1 - 3 (S544N) allele and prepared a weak pol - 6 pll1 - 3 . About 5% of pol - 6 pll1 - 3 seedlings continued the post-embryonic development displaying short roots with reduced root meristem, wuschel -like adventitious phyllotaxis, and defective flowers lacking carpel. The clv1 , clv2 , and clv3 phenotypes led by enlarged shoot meristems were almost completely suppressed in the pol -6 pll1 - 3 . POL / PLL1 were required for the indeterminate floral organ development displayed by agamous . PLL1-GFP asymmetrically localized in the shootward sides of columella cells and increased the size of distal root meristem region by enhancing the WUS - RELATED HOMEOBOX 5 expression suggesting that PLL1 might provide the stem cells and progenies with proper positional information for the asymmetric cell divisions. Conclusion Together, POL/PLL1 are required for the maintenance of stem cell pools for the post-embryonic development in Arabidopsis.