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.
Sci Rep. 2016 Mar 29;6:23586. 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.
种子萌发后，为了进行主根生长，需要激活根分生组织。我们研究了拟南芥种子萌发过程中根分生组织激活的激素和遗传调控。在最佳条件下，胚根细胞分裂仅在萌发完成后发生，并且需要从头合成 GA。当萌发被 ABA 阻断时，胚根伸长和细胞分裂发生在这些未萌发的种子中。相反，在 GA 有限的条件下，ABA 不敏感突变体在没有胚根分生组织激活和生长的情况下完成萌发。因此，胚根分生组织的激活和延伸可以独立于萌发的发育转变的完成。细胞周期调控因子 KRP6 部分抑制 GA 依赖性细胞周期的激活。krp6 突变体种子的萌发发生得更快，在剂量反应测定中对 ABA 的敏感性略低，但对 GA 合成抑制剂 PAC 也高度敏感。这些相互矛盾的表型表明，细胞周期在萌发的拟南芥种子中解耦了 GA 和 ABA 的反应，并且 KRP6 在 GA 下游起作用，以抑制萌发过程中的有丝分裂细胞周期激活。
