title: Re-induction of the cell cycle in the Arabidopsis post-embryonic root meristem is ABA-insensitive, GA-dependent and repressed by KRP6.
abstract: Seeding establishment following seed germination requires activation of the root meristem for primary root growth. We investigated the hormonal and genetic regulation of root meristem activation during Arabidopsis seed germination. In optimal conditions, radicle cell divisions occur only after the completion of germination and require de novo GA synthesis. When the completion of germination is blocked by ABA, radicle elongation and cell divisions occurred in these non-germinating seeds. Conversely under GA-limiting conditions, ABA-insensitive mutants complete germination in the absence of radicle meristem activation and growth. Radicle meristem activation and extension can therefore occur independently of completion of the developmental transition of germination. The cell cycle regulator KRP6 partially represses GA-dependent activation of the cell cycle. Germination of krp6 mutant seeds occurs more rapidly, is slightly insensitive to ABA in dose-response assays, but also hypersensitive to the GA synthesis inhibitor PAC. These conflicting phenotypes suggest the cell cycle uncouples GA and ABA responses in germinating Arabidopsis seeds, and that KRP6 acts downstream of GA to inhibit mitotic cell cycle activation during germination.
authors.affiliation: School of Biosciences, Sir Martin Evans Building, Cardiff University, Museum Avenue, Cardiff CF10 3AX, Wales, UK.|School of Applied Sciences, University of South Wales, Pontypridd, CF37 4AT, United Kingdom.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Nieuwland
authors.affiliation: School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: Petra
authors.initials: P
authors.lastname: Stamm
authors.affiliation: School of Biosciences, Sir Martin Evans Building, Cardiff University, Museum Avenue, Cardiff CF10 3AX, Wales, UK.
authors.forename: Bo
authors.initials: B
authors.lastname: Wen
authors.affiliation: School of Biosciences, Sir Martin Evans Building, Cardiff University, Museum Avenue, Cardiff CF10 3AX, Wales, UK.
authors.forename: Ricardo S
authors.initials: RS
authors.lastname: Randall
authors.affiliation: School of Biosciences, Sir Martin Evans Building, Cardiff University, Museum Avenue, Cardiff CF10 3AX, Wales, UK.
authors.forename: James A H
authors.initials: JA
authors.lastname: Murray
authors.affiliation: School of Biosciences, University of Birmingham, Birmingham B15 2TT, United Kingdom.
authors.forename: George W
authors.initials: GW
authors.lastname: Bassel
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects* / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018525:Germination / Q000187:drug effects / Q000235:genetics; D005875:Gibberellins / Q000494:pharmacology*; D018519:Meristem / Q000187:drug effects* / Q000235:genetics; D018613:Microscopy, Confocal; D009154:Mutation; D010937:Plant Growth Regulators / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects* / Q000235:genetics; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000187:drug effects / Q000235:genetics; D012639:Seeds / Q000187:drug effects / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D005875:Gibberellins; C587773:KRP6 protein, Arabidopsis; D010937:Plant Growth Regulators; D000040:Abscisic Acid; C007842:gibberellic acid