Root architecture is a major determinant of plant fitness and is under constant modification in response to favorable and unfavorable environmental stimuli. Beyond impacts on the primary root, the environment can alter the position, spacing, density, and length of secondary or lateral roots. Lateral root development is among the best-studied examples of plant organogenesis, yet there are still many unanswered questions about its earliest steps. Among the challenges faced in capturing these first molecular events is the fact that this process occurs in a small number of cells with unpredictable timing. Single-cell sequencing methods afford the opportunity to isolate the specific transcriptional changes occurring in cells undergoing this fate transition. Using this approach, we successfully captured the transcriptomes of initiating lateral root primordia in Arabidopsis thaliana and discovered many upregulated genes associated with this process. We developed a method to selectively repress target gene transcription in the xylem pole pericycle cells where lateral roots originate and demonstrated that the expression of several of these targets is required for normal root development. We also discovered subpopulations of cells in the pericycle and endodermal cell files that respond to lateral root initiation, highlighting the coordination across cell files required for this fate transition.

 摘 要 

植物根的结构是决定植物适应性的一个主要因素，并且处于对有利和不利的环境刺激响应的不断变化中。除了对主根的生长产生影响，环境还能够改变次生根或侧根的位置、间距、密度和长度。侧根的发育是植物器官发生研究的比较深入的组织之一，但是对于其早期的过程仍然还有需要问题需要解开。在捕获侧根早期发生分子事件的一个难点在于这些进程通常指发生在一小部分的细胞中，并且具有时间上的不可预测性。单细胞测序方法使得我们能够在植物发生此类命运转变时期，分离出特定的转录变化。利用该方法，作者成功捕获了拟南芥侧根原基起始过程中的转录组，并且发现了许多与该进程相关的上调表达基因。作者开发了一种选择性抑制侧根起源的木质部极的中柱鞘细胞中靶基因转录的方法，并证明了这些靶基因的表达是正常根系发育所必需的。作者还发现了一类中柱鞘和内皮层细胞的亚亚细胞群，响应于侧根的起始，表明植物的侧根起始这种命运转变需要不同细胞类型的协调。