title: A molecular switch for initiating cell differentiation in Arabidopsis.
abstract: BACKGROUND
  The onset of differentiation entails modifying the gene expression state of cells, to allow activation of developmental programs that are maintained repressed in the undifferentiated precursor cells [1, 2]. This requires a mechanism to change gene expression on a genome-scale. Recent evidence suggests that in mammalian stem cells, derepression of developmental regulators during differentiation involves a shift from stalled to productive elongation of their transcripts [3-5], but factors mediating this shift have not been identified and the evidence remains correlative.
  
  
  RESULTS
  We report the identification of the MINIYO (IYO) gene, a positive regulator of transcriptional elongation that is essential for cells to initiate differentiation in Arabidopsis. IYO interacts with RNA polymerase II and the Elongator complex and is required to sustain global levels of transcriptional elongation activity, specifically in differentiating tissues. Accordingly, IYO is expressed in embryos, meristems, and organ primordia and not in mature tissues. Moreover, differential subcellular protein distribution further refines the domain of IYO function by directing nuclear accumulation, and thus its transcriptional activity, to cells initiating differentiation. Importantly, IYO overexpression induces premature cell differentiation and leads to meristem termination phenotypes.
  
  
  CONCLUSIONS
  These findings identify IYO as a necessary and sufficient factor for initiating differentiation in Arabidopsis and suggest that the targeted nuclear accumulation of IYO functions as a transcriptional switch for this fate transition.
authors.affiliation: Centro Nacional de Biotecnología-CSIC, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Maite
authors.initials: M
authors.lastname: Sanmartín
authors.forename: Michael
authors.initials: M
authors.lastname: Sauer
authors.forename: Alfonso
authors.initials: A
authors.lastname: Muñoz
authors.forename: Jan
authors.initials: J
authors.lastname: Zouhar
authors.forename: Angel
authors.initials: A
authors.lastname: Ordóñez
authors.forename: Wilhelmina T G
authors.initials: WT
authors.lastname: van de Ven
authors.forename: Elena
authors.initials: E
authors.lastname: Caro
authors.forename: María
authors.initials: M
authors.lastname: de la Paz Sánchez
authors.forename: Natasha V
authors.initials: NV
authors.lastname: Raikhel
authors.forename: Crisanto
authors.initials: C
authors.lastname: Gutiérrez
authors.forename: José J
authors.initials: JJ
authors.lastname: Sánchez-Serrano
authors.forename: Enrique
authors.initials: E
authors.lastname: Rojo
mesh_terms: D017360:Arabidopsis / Q000166:cytology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology*; D018519:Meristem / Q000166:cytology; D009154:Mutation; D014158:Transcription, Genetic
chemical_list: D029681:Arabidopsis Proteins