title: Brassinosteroids regulate organ boundary formation in the shoot apical meristem of Arabidopsis.
abstract: Spatiotemporal control of the formation of organ primordia and organ boundaries from the stem cell niche in the shoot apical meristem (SAM) determines the patterning and architecture of plants, but the underlying signaling mechanisms remain poorly understood. Here we show that brassinosteroids (BRs) play a key role in organ boundary formation by repressing organ boundary identity genes. BR-hypersensitive mutants display organ-fusion phenotypes, whereas BR-insensitive mutants show enhanced organ boundaries. The BR-activated transcription factor BZR1 directly represses the cup-shaped cotyledon (CUC) family of organ boundary identity genes. In WT plants, BZR1 accumulates at high levels in the nuclei of central meristem and organ primordia but at a low level in organ boundary cells to allow CUC gene expression. Activation of BR signaling represses CUC gene expression and causes organ fusion phenotypes. This study uncovers a role for BR in the spatiotemporal control of organ boundary formation and morphogenesis in the SAM.
authors.affiliation: Department of Plant Biology, Carnegie Institution for Science, Stanford, CA 94305, USA.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Gendron
authors.forename: Jiang-Shu
authors.initials: JS
authors.lastname: Liu
authors.forename: Min
authors.initials: M
authors.lastname: Fan
authors.forename: Ming-Yi
authors.initials: MY
authors.lastname: Bai
authors.forename: Stephan
authors.initials: S
authors.lastname: Wenkel
authors.forename: Patricia S
authors.initials: PS
authors.lastname: Springer
authors.forename: M Kathryn
authors.initials: MK
authors.lastname: Barton
authors.forename: Zhi-Yong
authors.initials: ZY
authors.lastname: Wang
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism; D060406:Brassinosteroids / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D047369:Chromatin Immunoprecipitation; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018519:Meristem / Q000502:physiology*; D018613:Microscopy, Confocal / Q000379:methods; D008855:Microscopy, Electron, Scanning / Q000379:methods; D009154:Mutation; D010641:Phenotype; D018520:Plant Shoots / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D060406:Brassinosteroids