Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apartado Postal 510-3, 62250, Cuernavaca, Morelos, Mexico.
Planta. 2011 Dec;234(6):1163-77. doi: 10.1007/s00425-011-1470-4. Epub 2011 Jul 9.
An indeterminate developmental program allows plant organs to grow continuously by maintaining functional meristems over time. The molecular mechanisms involved in the maintenance of the root apical meristem are not completely understood. We have identified a new Arabidopsis thaliana mutant named moots koom 1 (mko1) that showed complete root apical meristem exhaustion of the primary root by 9 days post-germination. MKO1 is essential for maintenance of root cell proliferation. In the mutant, cell division is uncoupled from cell growth in the region corresponding to the root apical meristem. We established the sequence of cellular events that lead to meristem exhaustion in this mutant. Interestingly, the SCR and WOX5 promoters were active in the mko1 quiescent center at all developmental stages. However, during meristem exhaustion, the mutant root tip showed defects in starch accumulation in the columella and changes in auxin response pattern. Therefore, contrary to many described mutants, the determinate growth in mko1 seedlings does not appear to be a consequence of incorrect establishment or affected maintenance of the quiescent center but rather of cell proliferation defects both in stem cell niche and in the rest of the apical meristem. Our results support a model whereby the MKO1 gene plays an important role in the maintenance of the root apical meristem proliferative capacity and indeterminate root growth, which apparently acts independently of the SCR/SHR and WOX5 regulatory pathways.
不定型发育程序使植物器官通过随时间维持功能分生组织而不断生长。维持根尖分生组织的分子机制尚未完全了解。我们已经鉴定出一种新的拟南芥突变体，命名为 moots koom1（mko1），该突变体在发芽后 9 天表现出主根根尖分生组织完全耗尽。MKO1 对维持根细胞增殖是必需的。在突变体中，细胞分裂与根尖分生组织相应区域的细胞生长解耦。我们建立了导致该突变体分生组织耗尽的细胞事件序列。有趣的是，SCR 和 WOX5 启动子在 mko1 静止中心的所有发育阶段都活跃。然而，在分生组织耗尽期间，突变体根尖显示出柱细胞中淀粉积累缺陷和生长素反应模式改变。因此，与许多描述的突变体不同，mko1 幼苗中的限定生长似乎不是静止中心建立不正确或维持受到影响的结果，而是干细胞龛和根尖分生组织其余部分的细胞增殖缺陷的结果。我们的结果支持这样一种模型，即 MKO1 基因在维持根尖分生组织增殖能力和不定型根生长方面发挥着重要作用，这显然独立于 SCR/SHR 和 WOX5 调控途径。
