Laboratory of Biochemistry, Wageningen University, 6708 WE Wageningen, The Netherlands.
Department of Plant Biotechnology and Bioinformatics, Ghent University, 9052 Ghent, Belgium.
Proc Natl Acad Sci U S A. 2017 Oct 17;114(42):E8922-E8929. doi: 10.1073/pnas.1707400114. Epub 2017 Oct 2.
In plants, apical meristems allow continuous growth along the body axis. Within the root apical meristem, a group of slowly dividing quiescent center cells is thought to limit stem cell activity to directly neighboring cells, thus endowing them with unique properties, distinct from displaced daughters. This binary identity of the stem cells stands in apparent contradiction to the more gradual changes in cell division potential and differentiation that occur as cells move further away from the quiescent center. To address this paradox and to infer molecular organization of the root meristem, we used a whole-genome approach to determine dominant transcriptional patterns along root ontogeny zones. We found that the prevalent patterns are expressed in two opposing gradients. One is characterized by genes associated with development, the other enriched in differentiation genes. We confirmed these transcript gradients, and demonstrate that these translate to gradients in protein accumulation and gradual changes in cellular properties. We also show that gradients are genetically controlled through multiple pathways. Based on these findings, we propose that cells in the root meristem gradually transition from stem cell activity toward differentiation.
在植物中,顶端分生组织允许沿着体轴进行持续生长。在根顶端分生组织中,一群缓慢分裂的静止中心细胞被认为将干细胞活性限制在直接相邻的细胞中,从而赋予它们独特的特性,与被取代的子细胞不同。这种干细胞的二元身份与细胞分裂潜能和分化的更渐进变化明显矛盾,这些变化发生在细胞远离静止中心时。为了解决这个矛盾,并推断根分生组织的分子组织,我们使用全基因组方法来确定沿根发生区的主要转录模式。我们发现,主要模式以两种相反的梯度表达。一种是与发育相关的基因特征,另一种是分化基因丰富。我们证实了这些转录梯度,并证明它们转化为蛋白质积累的梯度和细胞特性的逐渐变化。我们还表明,梯度通过多种途径受到遗传控制。基于这些发现,我们提出根分生组织中的细胞逐渐从干细胞活性向分化转变。