Department of Plant Molecular Biology, University of Lausanne, 1015 Lausanne, Switzerland.
ZMBP-Center for Plant Molecular Biology, University of Tuebingen, Auf der Morgenstelle 32, 72076 Tuebingen, Germany.
Curr Biol. 2021 Mar 8;31(5):965-977.e5. doi: 10.1016/j.cub.2020.11.070. Epub 2021 Feb 1.
Plants deposit hydrophobic polymers, such as lignin or suberin, in their root cell walls to protect inner tissues and facilitate selective uptake of solutes. Insights into how individual root tissues contribute to polymer formation are important for elucidation of ultrastructure, function, and development of these protective barriers. Although the pathways responsible for production of the barrier constituents are established, our models lack spatiotemporal resolution-especially in roots-thus, the source of monomeric barrier components is not clear. This is mainly due to our restricted ability to manipulate synthesis of the broadly important phenylpropanoid pathway, as mutants in this pathway display lethal or pleiotropic phenotypes. Here, we overcome this challenge by exploiting highly controlled in vivo repression systems. We provide strong evidence that autonomous production of phenylpropanoids is essential for establishment of the endodermal Casparian strip as well as adherence of the suberin matrix to the cell wall of endodermis and cork. Our work highlights that, in roots, the phenylpropanoid pathway is under tight spatiotemporal control and serves distinct roles in barrier formation across tissues and developmental zones. This becomes evident in the late endodermis, where repression of phenylpropanoid production leads to active removal of suberin in pre-suberized cells, indicating that endodermal suberin depositions might embody a steady state between continuous synthesis and degradation.
植物在其根细胞壁中沉积疏水性聚合物，如木质素或角质，以保护内部组织并促进溶质的选择性吸收。深入了解单个根组织如何有助于聚合物的形成，对于阐明这些保护屏障的超微结构、功能和发育是很重要的。尽管负责产生屏障成分的途径已经确定，但我们的模型缺乏时空分辨率——特别是在根部——因此，单体屏障成分的来源尚不清楚。这主要是由于我们操纵广泛重要的苯丙烷途径合成的能力有限，因为该途径的突变体表现出致死或多效表型。在这里，我们通过利用高度受控的体内抑制系统来克服这一挑战。我们提供了强有力的证据表明，苯丙烷的自主产生对于内皮层 Casparian 条带的建立以及角质层基质与内皮层和软木细胞壁的附着是必不可少的。我们的工作表明，在根部，苯丙烷途径受到严格的时空控制，并在不同组织和发育区域的屏障形成中发挥不同的作用。这在内皮层后期变得明显，其中苯丙烷产生的抑制导致预角质化细胞中角质的主动去除，表明内皮层角质的沉积可能体现了连续合成和降解之间的稳定状态。
