title: Azacytidine and miR156 promote rooting in adult but not in juvenile Arabidopsis tissues.
abstract: Poor adventitious root (AR) formation is a major obstacle in micropropagation and conventional vegetative propagation of many crops. It is affected by many endogenous and exogenous factors. With respect to endogenous factors, the phase change from juvenile to adult has a major influence on AR formation and rooting is usually much reduced or even fully inhibited in adult tissues. It has been reported that the phase change is characterized by an increase in DNA-methylation and a decrease in the expression of microRNA156 (miR156). In this paper, we examined the effect of azacytidine (AzaC) and miR156 on AR formation in adult and juvenile Arabidopsis tissues. To identify the ontogenetic state researchers have used flowering or leaf morphology. We have used the rootability which allows - in contrast with both other characteristics- to examine the ontogenetic state at the cellular level. Overexpression of miR156 promoted only the rooting of adult tissues indicating that the phase change-associated loss in tissues' competence to develop ARs is also under the control of miR156. Azacytidine inhibits DNA methylation during DNA replication. Azacytidine treatment also promoted AR formation in nonjuvenile tissues but had no or little effect in juvenile tissues. Its addition during seedling growth (by which all tissues become hypomethylated) or during the rooting treatment (by which only those cells become hypomethylated that are generated after taking the explant) are both effective in the promotion of rooting. An AzaC treatment may be useful in tissue culture for crops that are recalcitrant to root.
authors.affiliation: Wageningen UR Plant Breeding, Wageningen University and Research Centre, PO Box 386, 6700 AJ Wageningen, the Netherlands. Electronic address: mehdi.massoumi@wur.nl.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Massoumi
authors.affiliation: Wageningen UR Plant Breeding, Wageningen University and Research Centre, PO Box 386, 6700 AJ Wageningen, the Netherlands.
authors.forename: Frans A
authors.initials: FA
authors.lastname: Krens
authors.affiliation: Wageningen UR Plant Breeding, Wageningen University and Research Centre, PO Box 386, 6700 AJ Wageningen, the Netherlands.
authors.forename: Richard G F
authors.initials: RG
authors.lastname: Visser
authors.affiliation: Wageningen UR Plant Breeding, Wageningen University and Research Centre, PO Box 386, 6700 AJ Wageningen, the Netherlands.
authors.forename: Geert-Jan M
authors.initials: GM
authors.lastname: De Klerk
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D001374:Azacitidine / Q000494:pharmacology*; D019175:DNA Methylation; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D035683:MicroRNAs / Q000235:genetics*; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D030821:Plants, Genetically Modified; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D035683:MicroRNAs; C559759:Mirn156 microRNA, Arabidopsis; D001374:Azacitidine
keywords: Adventitious root formation; Arabidopsis thaliana; Hypomethylation; Juvenile; Phase change; miR156