The effects of brassinosteroid signaling on shoot and root development have been characterized in great detail but a simple consistent positive or negative impact on a basic cellular parameter was not identified. In this study, we combined digital 3D single-cell shape analysis and single-cell mRNA sequencing to characterize root meristems and mature root segments of brassinosteroid-blind mutants and wild type. The resultant datasets demonstrate that brassinosteroid signaling affects neither cell volume nor cell proliferation capacity. Instead, brassinosteroid signaling is essential for the precise orientation of cell division planes and the extent and timing of anisotropic cell expansion. Moreover, we found that the cell-aligning effects of brassinosteroid signaling can propagate to normalize the anatomy of both adjacent and distant brassinosteroid-blind cells through non-cell-autonomous functions, which are sufficient to restore growth vigor. Finally, single-cell transcriptome data discern directly brassinosteroid-responsive genes from genes that can react non-cell-autonomously and highlight arabinogalactans as sentinels of brassinosteroid-dependent anisotropic cell expansion.

油菜素内酯信号对枝条和根发育的影响已被详细描述，但未确定对基本细胞参数的简单一致的积极或消极影响。在这项研究中，我们结合数字 3D 单细胞形状分析和单细胞 mRNA 测序来表征油菜素内酯盲突变体和野生型的根分生组织和成熟根段。所得数据集表明油菜素内酯信号既不影响细胞体积也不影响细胞增殖能力。相反，油菜素内酯信号传导对于细胞分裂平面的精确定位以及各向异性细胞扩张的程度和时间至关重要。而且，我们发现油菜素类固醇信号的细胞排列效应可以通过非细胞自主功能传播以使相邻和远处的油菜素类固醇盲细胞的解剖结构正常化，这足以恢复生长活力。最后，单细胞转录组数据直接从可以非细胞自主反应的基因中辨别油菜素类固醇反应基因，并突出阿拉伯半乳聚糖作为依赖油菜素类固醇的各向异性细胞扩增的哨兵。