Lakehal Abdellah, Dob Asma, Beeckman Tom
Ghent University, Department of Plant Biotechnology and Bioinformatics, 9052 Ghent, Belgium; VIB Center for Plant Systems Biology, 9052 Ghent, Belgium.
Ghent University, Department of Plant Biotechnology and Bioinformatics, 9052 Ghent, Belgium; VIB Center for Plant Systems Biology, 9052 Ghent, Belgium.
Curr Biol. 2023 Mar 13;33(5):R170-R175. doi: 10.1016/j.cub.2022.12.054.
Plants have evolved a remarkable capacity to develop new organs post-embryonically throughout their lifespan. A prime example of this is root branching. Root branching occurs in two ways: dichotomous and lateral branching. The dichotomous branching is the result of the division of the root apical meristem into two daughter meristems, likely through symmetric cell divisions of the root apical cell, as has recently been illustrated in the extant lycophyte Selaginella moellendorffii (Figure 1). Lateral root branching relies on the de novo specification of a subset of founder cells (hereinafter referred to as lateral root stem cells) located in the internal tissues of an existing root. This step is followed by initiation, in which the specified cells re-enter the cell cycle, and subsequently by primordium formation and emergence. In this primer, we summarize recent advances describing the molecular bases underlying lateral root stem cell specification in angiosperms and highlight the important positional signals that fine tune this process. By delving into the evolutionary origins of root branching, we point out that positional control of lateral root stem cell specification has not been the prevailing mechanism among all plants and discuss the process in ferns (i.e., a sister group of seed plants), where it seems to be under the control of lineage-dependent mechanisms.
植物在其整个生命周期中都进化出了在胚胎后期发育新器官的非凡能力。根分支就是一个典型例子。根分支有两种方式：二叉分支和侧根分支。二叉分支是根尖分生组织分裂为两个子分生组织的结果，这可能是通过根尖细胞的对称细胞分裂实现的，最近在现存的石松类植物卷柏中得到了证实（图1）。侧根分支依赖于位于现有根内部组织中的一部分起始细胞（以下简称侧根干细胞）的重新特化。这一步之后是起始阶段，即特定细胞重新进入细胞周期，随后是原基形成和出现。在本入门文章中，我们总结了描述被子植物侧根干细胞特化分子基础的最新进展，并强调了微调这一过程的重要位置信号。通过深入研究根分支的进化起源，我们指出侧根干细胞特化的位置控制并非所有植物的普遍机制，并讨论了蕨类植物（即种子植物的姐妹类群）中的这一过程，在蕨类植物中，它似乎受谱系依赖机制的控制。
