title: Origin, timing, and gene expression profile of adventitious rooting in Arabidopsis hypocotyls and stems.
abstract: OBJECTIVE
  Adventitious root (AR) formation is indispensable for vegetative propagation, but difficult to achieve in many crops. Understanding its molecular mechanisms is thus important for such species. Here we aimed at developing a rooting protocol for direct AR formation in stems, locating cellular AR origins in stems and exploring molecular differences underlying adventitious rooting in hypocotyls and stems.
  
  
  METHODS
  In-vitro-grown hypocotyls or stems of wild-type and transgenic ecotype Columbia (Col-0) of Arabidopsis thaliana were rooted on rooting media. Anatomy of AR formation, qRT-PCR of some rooting-related genes and in situ GUS expression were carried out during rooting from hypocotyls and stems.
  
  
  RESULTS
  We developed a rooting protocol for AR formation in stems and traced back root origins in stems by anatomical and in situ expression studies. Unlike rooting in hypocotyls, rooting in stems was slower, and AR origins were mainly from lateral parenchyma of vascular bundles and neighboring starch sheath cells as well as, to a lesser extent, from phloem cap and xylem parenchyma. Transcript levels of GH3-3, LBD16, LBD29, and LRP1 in hypocotyls and stems were similar, but transcript accumulation was delayed in stems. In situ expression signals of DR5::GUS, LBD16::GUS, LBD29::GUS, and rolB::GUS reporters in stems mainly occurred at the root initiation sites, suggesting their involvement in AR formation.
  
  
  CONCLUSIONS
  We have developed an efficient rooting protocol using half-strength Lepoivre medium for studying AR formation in stems, traced back the cellular AR origins in stems, and correlated expression of rooting-related genes with root initiation sites.
authors: Department of Plant Breeding, Swedish University of Agricultural Sciences, Box 101, SE-230 53 Alnarp, Sweden.
authors: Margareta
authors: M
authors: Welander
authors: Thomas
authors: T
authors: Geier
authors: Anders
authors: A
authors: Smolka
authors: Annelie
authors: A
authors: Ahlman
authors: Jing
authors: J
authors: Fan
authors: Li-Hua
authors: LH
authors: Zhu
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D060146:Ecotype; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D018546:Hypocotyl / Q000254:growth & development*; D018519:Meristem / Q000254:growth & development; D059828:Plant Cells; D018517:Plant Roots / Q000254:growth & development*; D018547:Plant Stems / Q000254:growth & development*; D058526:Plant Vascular Bundle; D030821:Plants, Genetically Modified; D059467:Transcriptome
chemical_list: D029681:Arabidopsis Proteins
keywords: Arabidopsis thaliana; Brassicaceae; Col-0; adventitious root formation; ecotype Columbia, hypocotyl; stem; temporal-spatial gene expression