title: POLTERGEIST encodes a protein phosphatase 2C that regulates CLAVATA pathways controlling stem cell identity at Arabidopsis shoot and flower meristems.
abstract: BACKGROUND
  Receptor kinases are a large gene family in plants and have more than 600 members in Arabidopsis. Receptor kinases in plants regulate a broad range of developmental processes, including steroid hormone perception, organ elongation, self-incompatibility, and abscission. Intracellular signaling components for receptor kinases in plants are largely unknown. The CLAVATA 1 (CLV1) receptor kinase in Arabidopsis regulates stem cell identity and differentiation through its repression of WUSCHEL (WUS) expression. Mutations at the POLTERGEIST (POL) gene were previously described as phenotypic suppressors of mutations within the CLV1 gene. Genetic evidence placed POL as a downstream regulator of CLAVATA1 signaling.
  
  
  RESULTS
  We provide evidence that POL functions in both the CLV1-WUS pathway and a novel WUS-independent CLV1 pathway regulating stem cell identity. We demonstrate that POL encodes a protein phosphatase 2C (PP2C) with a predicted nuclear localization sequence, indicating that it has a role in signal transduction downstream of the CLV1 receptor. The N terminus of POL has a possible regulatory function, and the C terminus has PP2C-like phosphatase catalytic activity. Although the POL catalytic domain is conserved in other PP2Cs, the POL protein represents a unique subclass of plant PP2Cs. POL is broadly expressed throughout the plant.
  
  
  CONCLUSIONS
  POL represents a novel component of the CLV1 receptor kinase signaling pathway. The ubiquitous expression of POL and pol phenotypes outside the meristem suggest that POL may be a common regulator of many signaling pathways.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
authors.forename: Lita P
authors.initials: LP
authors.lastname: Yu
authors.forename: Andrea K
authors.initials: AK
authors.lastname: Miller
authors.forename: Steven E
authors.initials: SE
authors.lastname: Clark
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000033:anatomy & histology / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D035264:Flowers / Q000033:anatomy & histology* / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000502:physiology*; D008969:Molecular Sequence Data; D012275:Oryza / Q000235:genetics / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D000071636:Protein Phosphatase 2C; D017346:Protein Serine-Threonine Kinases; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology; D014018:Tissue Distribution
chemical_list: D029681:Arabidopsis Proteins; D018398:Homeodomain Proteins; C116421:WUSCHEL protein, Arabidopsis; D020794:Receptor Protein-Tyrosine Kinases; C118166:CLV1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C