Re-induction of the cell cycle in the Arabidopsis post-embryonic root meristem is ABA-insensitive, GA-dependent and repressed by KRP6

• Published in: Scientific reports Vol. 6; no. 1; p. 23586
• Main Authors: Nieuwland, Jeroen, Stamm, Petra, Wen, Bo, Randall, Ricardo S., Murray, James A. H., Bassel, George W.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 29-03-2016; Nature Publishing Group
• Subjects: 14; 631/449/1741; 631/449/2653/1974; Abscisic acid; Abscisic Acid - pharmacology; Arabidopsis - drug effects; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cell activation; Cell cycle; Cell Cycle - drug effects; Cell Cycle - genetics; Elongation; Embryos; Gene Expression Regulation, Plant - drug effects; Germination - drug effects; Germination - genetics; Gibberellins - pharmacology; Humanities and Social Sciences; Meristem - drug effects; Meristem - genetics; Microscopy, Confocal; multidisciplinary; Mutation; Plant growth; Plant Growth Regulators - pharmacology; Plant Roots - drug effects; Plant Roots - genetics; Plants, Genetically Modified; Reverse Transcriptase Polymerase Chain Reaction; Science; Science (multidisciplinary); Seed germination; Seedlings - drug effects; Seedlings - genetics; Seeds; Seeds - drug effects; Seeds - genetics; Signal Transduction - drug effects; Signal Transduction - genetics
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep23586

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.