Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen, AB24 3UU, UK.
Department of Agronomy and Horticulture, University of Nebraska Lincoln, Lincoln, NE, 68588-0660, USA.
Sci Rep. 2019 Mar 12;9(1):4227. doi: 10.1038/s41598-019-40588-5.
The endodermis is a key cell layer in plant roots that contributes to the controlled uptake of water and mineral nutrients into plants. In order to provide such functionality the endodermal cell wall has specific chemical modifications consisting of lignin bands (Casparian strips) that encircle each cell, and deposition of a waxy-like substance (suberin) between the wall and the plasma membrane. These two extracellular deposits provide control of diffusion enabling the endodermis to direct the movement of water and solutes into and out of the vascular system in roots. Loss of integrity of the Casparian strip-based apoplastic barrier is sensed by the leakage of a small peptide from the stele into the cortex. Here, we report that such sensing of barrier integrity leads to the rebalancing of water and mineral nutrient uptake, compensating for breakage of Casparian strips. This rebalancing involves both a reduction in root hydraulic conductivity driven by deactivation of aquaporins, and downstream limitation of ion leakage through deposition of suberin. These responses in the root are also coupled to a reduction in water demand in the shoot mediated by ABA-dependent stomatal closure.
内皮层是植物根中的一个关键细胞层，有助于控制水分和矿质养分被植物吸收。为了提供这种功能，内皮层细胞壁具有特定的化学修饰，包括环绕每个细胞的木质素带（凯氏带）和在细胞壁和质膜之间沉积的蜡状物质（栓质）。这两种细胞外沉积物提供了扩散控制，使内皮层能够将水分和溶质引导到根中的维管束系统中，并从维管束系统中排出。基于凯氏带的质外体屏障完整性的丧失会导致从小柱向皮层泄漏一种小肽，从而被感知到。在这里，我们报告说，这种对屏障完整性的感知会导致水和矿物质养分吸收的再平衡，从而补偿凯氏带的破裂。这种再平衡既涉及通过水孔蛋白失活驱动的根水力传导率的降低，也涉及通过栓质沉积导致的离子泄漏的下游限制。这些在根中的反应也与通过依赖 ABA 的气孔关闭介导的地上部水分需求减少相关。
