Signaling for a weakness in cell walls Lateral roots form at regular intervals in the small mustard plant Arabidopsis thaliana. Wachsman et al. have now identified both pectin and subcellular vesicle trafficking as part of the oscillating signaling system that initiates lateral roots. Esterification of pectin regulates its function at the nascent lateral root site, altering the stiffness of cell walls and the strength of cell-cell adhesion. Because lateral root primordia must push through overlying cell layers, reduced cell adhesion at these sites might aid in the formation of lateral roots. Science, this issue p. 819 Periodic lateral root emergence is controlled by regulation of intercellular adhesion through pectin modifications. In Arabidopsis thaliana, lateral roots initiate in a process preceded by periodic gene expression known as the root clock. We identified the vesicle-trafficking regulator GNOM and its suppressor, ADENOSINE PHOSPHATE RIBOSYLATION FACTOR GTPase ACTIVATION PROTEIN DOMAIN3, as root clock regulators. GNOM is required for the proper distribution of pectin, a mediator of intercellular adhesion, whereas the pectin esterification state is essential for a functional root clock. In sites of lateral root primordia emergence, both esterified and de-esterified pectin variants are differentially distributed. Using a reverse-genetics approach, we show that genes controlling pectin esterification regulate the root clock and lateral root initiation. These results indicate that the balance between esterified and de-esterified pectin states is essential for proper root clock function and the subsequent initiation of lateral root primordia.

中文翻译：

---

细胞壁重塑和囊泡运输介导拟南芥的根时钟

细胞壁弱点的信号 侧根在小型芥菜植物拟南芥中定期形成。瓦克斯曼等人。现在已经确定果胶和亚细胞囊泡运输是启动侧根的振荡信号系统的一部分。果胶的酯化调节其在新生侧根部位的功能，改变细胞壁的硬度和细胞间粘附的强度。因为侧根原基必须穿过覆盖的细胞层，这些部位的细胞粘附减少可能有助于侧根的形成。科学，这个问题 p。819 周期性的侧根出现是通过果胶修饰调节细胞间粘附来控制的。在拟南芥中，侧根起始于称为根时钟的周期性基因表达之前的过程。我们确定了囊泡运输调节剂 GNOM 及其抑制因子磷酸腺苷核糖化因子 GTPase 激活蛋白域 3，作为根时钟调节剂。GNOM 是果胶正确分布所必需的，果胶是细胞间粘附的介质，而果胶酯化状态对于功能性根时钟至关重要。在侧根原基出现的部位，酯化和去酯化果胶变体的分布不同。使用反向遗传学方法，我们表明控制果胶酯化的基因调节根时钟和侧根起始。