Department of Experimental Plant Biology, Faculty of Science, Charles University, Prague, Czech Republic.
Institute of Cell and Interaction Biology, Heinrich-Heine-University Düsseldorf, Düsseldorf, Germany.
Elife. 2023 Jul 14;12:e85193. doi: 10.7554/eLife.85193.
Plant roots navigate in the soil environment following the gravity vector. Cell divisions in the meristem and rapid cell growth in the elongation zone propel the root tips through the soil. Actively elongating cells acidify their apoplast to enable cell wall extension by the activity of plasma membrane AHA H-ATPases. The phytohormone auxin, central regulator of gravitropic response and root development, inhibits root cell growth, likely by rising the pH of the apoplast. However, the role of auxin in the regulation of the apoplastic pH gradient along the root tip is unclear. Here, we show, by using an improved method for visualization and quantification of root surface pH, that the root surface pH shows distinct acidic and alkaline zones, which are not primarily determined by the activity of AHA H-ATPases. Instead, the distinct domain of alkaline pH in the root transition zone is controlled by a rapid auxin response module, consisting of the AUX1 auxin influx carrier, the AFB1 auxin co-receptor, and the CNCG14 calcium channel. We demonstrate that the rapid auxin response pathway is required for an efficient navigation of the root tip.
植物的根在土壤环境中沿着重力矢量方向生长。在顶端分生组织中的细胞分裂和伸长区中的快速细胞生长推动根尖穿过土壤。活跃伸长的细胞使质外体酸化，通过质膜 AHA H-ATP 酶的活性促进细胞壁的延伸。植物激素生长素是向重力性反应和根发育的中央调节剂，它抑制根细胞的生长，可能是通过提高质外体的 pH 值。然而，生长素在调节根尖质外体 pH 梯度中的作用尚不清楚。在这里，我们通过使用一种改进的可视化和定量根表面 pH 的方法表明，根表面 pH 值显示出明显的酸性和碱性区，这些区域不是主要由 AHA H-ATP 酶的活性决定的。相反，根过渡区中碱性 pH 的独特区域由一个快速生长素反应模块控制，该模块由 AUX1 生长素流入载体、AFB1 生长素共受体和 CNCG14 钙通道组成。我们证明，快速生长素反应途径是根端有效导航所必需的。
