title: Patterns of auxin transport and gene expression during primordium development revealed by live imaging of the Arabidopsis inflorescence meristem.
abstract: BACKGROUND
  Plants produce leaf and flower primordia from a specialized tissue called the shoot apical meristem (SAM). Genetic studies have identified a large number of genes that affect various aspects of primordium development including positioning, growth, and differentiation. So far, however, a detailed understanding of the spatio-temporal sequence of events leading to primordium development has not been established.
  
  
  RESULTS
  We use confocal imaging of green fluorescent protein (GFP) reporter genes in living plants to monitor the expression patterns of multiple proteins and genes involved in flower primordial developmental processes. By monitoring the expression and polarity of PINFORMED1 (PIN1), the auxin efflux facilitator, and the expression of the auxin-responsive reporter DR5, we reveal stereotypical PIN1 polarity changes which, together with auxin induction experiments, suggest that cycles of auxin build-up and depletion accompany, and may direct, different stages of primordium development. Imaging of multiple GFP-protein fusions shows that these dynamics also correlate with the specification of primordial boundary domains, organ polarity axes, and the sites of floral meristem initiation.
  
  
  CONCLUSIONS
  These results provide new insight into auxin transport dynamics during primordial positioning and suggest a role for auxin transport in influencing primordial cell type.
authors.affiliation: Division of Biology, California Institute of Technology, Pasadena 91125, USA.
authors.forename: Marcus G
authors.initials: MG
authors.lastname: Heisler
authors.forename: Carolyn
authors.initials: C
authors.lastname: Ohno
authors.forename: Pradeep
authors.initials: P
authors.lastname: Das
authors.forename: Patrick
authors.initials: P
authors.lastname: Sieber
authors.forename: Gonehal V
authors.initials: GV
authors.lastname: Reddy
authors.forename: Jeff A
authors.initials: JA
authors.lastname: Long
authors.forename: Elliot M
authors.initials: EM
authors.lastname: Meyerowitz
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism; D017931:DNA Primers; D035264:Flowers / Q000254:growth & development* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D018519:Meristem / Q000378:metabolism*; D018613:Microscopy, Confocal; D008954:Models, Biological
chemical_list: D029681:Arabidopsis Proteins; C107294:CUC2 protein, Arabidopsis; D017931:DNA Primers; D018398:Homeodomain Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis; C097496:STM protein, Arabidopsis; D049452:Green Fluorescent Proteins