title: Gene silencing in Arabidopsis spreads from the root to the shoot, through a gating barrier, by template-dependent, nonvascular, cell-to-cell movement.
abstract: Upward long-distance mobile silencing has been shown to be phloem mediated in several different solanaceous species. We show that the Arabidopsis (Arabidopsis thaliana) seedling grafting system and a counterpart inducible system generate upwardly spreading long-distance silencing that travels not in the phloem but by template-dependent reiterated short-distance cell-to-cell spread through the cells of the central stele. Examining the movement of the silencing front revealed a largely unrecognized zone of tissue, below the apical meristem, that is resistant to the silencing signal and that may provide a gating or protective barrier against small RNA signals. Using a range of auxin and actin transport inhibitors revealed that, in this zone, alteration of vesicular transport together with cytoskeleton dynamics prevented or retarded the spread of the silencing signal. This suggests that small RNAs are transported from cell to cell via plasmodesmata rather than diffusing from their source in the phloem.
authors.affiliation: Commonwealth Scientific and Industrial Research Organization Plant Industry, Canberra, Australian Capital Territory 2601, Australia. dacheng.liang@csiro.au
authors.forename: Dacheng
authors.initials: D
authors.lastname: Liang
authors.forename: Rosemary G
authors.initials: RG
authors.lastname: White
authors.forename: Peter M
authors.initials: PM
authors.lastname: Waterhouse
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D001692:Biological Transport / Q000187:drug effects; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D018525:Germination / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018546:Hypocotyl / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D018519:Meristem / Q000187:drug effects / Q000378:metabolism; D008954:Models, Biological; D009711:Nucleotides / Q000378:metabolism; D010641:Phenotype; D052585:Phloem / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010937:Plant Growth Regulators / Q000494:pharmacology; D018517:Plant Roots / Q000737:chemistry / Q000187:drug effects / Q000235:genetics*; D018520:Plant Shoots / Q000166:cytology / Q000187:drug effects / Q000235:genetics*; D058526:Plant Vascular Bundle / Q000166:cytology / Q000187:drug effects / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D013698:Templates, Genetic; D013997:Time Factors
chemical_list: D007210:Indoleacetic Acids; D009711:Nucleotides; D010937:Plant Growth Regulators; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D049452:Green Fluorescent Proteins; D003907:Dexamethasone