Casparian strips (CSs) are cell wall modifications of vascular plants restricting extracellular free diffusion into and out of the vascular system [1]. This barrier plays a critical role in controlling the acquisition of nutrients and water necessary for normal plant development [2, 3, 4, 5]. CSs are formed by the precise deposition of a band of lignin approximately 2 μm wide and 150 nm thick spanning the apoplastic space between adjacent endodermal cells [6, 7]. Here, we identified a copper-containing protein, Uclacyanin1 (UCC1), that is sub-compartmentalized within the CS. UCC1 forms a central CS nanodomain in comparison with other CS-located proteins that are found to be mainly accumulated at the periphery of the CS. We found that loss-of-function of two uclacyanins (UCC1 and UCC2) reduces lignification specifically in this central CS nanodomain, revealing a nano-compartmentalized machinery for lignin polymerization. This loss of lignification leads to increased endodermal permeability and, consequently, to a loss of mineral nutrient homeostasis.

凯氏带 (CS) 是维管植物的细胞壁修饰，限制细胞外自由扩散进出维管系统 [1]。该屏障在控制植物正常发育所需的养分和水的获取方面发挥着关键作用[2,3,4,5]。CS 是由一条约 2 μm 宽、150 nm 厚的木质素带精确沉​​积而成，横跨相邻内胚层细胞之间的质外体空间 [6, 7]。在这里，我们鉴定了一种含铜蛋白 Uclacyin1 (UCC1)，它在 CS 内进行了亚区室化。与其他位于 CS 的蛋白质相比，UCC1 形成了一个中心 CS 纳米结构域，而其他蛋白质主要积累在 CS 的外围。我们发现，两个 uccyanins（ UCC1和UCC2 ）的功能丧失会减少该中心 CS 纳米域中的木质化，揭示了木质素聚合的纳米区室化机制。这种木质化的丧失导致内胚层渗透性增加，从而导致矿物质营养稳态的丧失。