背景回顾：Vascular plants reinforce the cell walls of the different xylem cell types with lignin phenolic polymers. Distinct lignin chemistries differ between each cell wall layer and each cell type to support their specific functions. 

提出问题：Yet the mechanisms controlling the tight spatial localization of specific lignin chemistries remain unclear. 

现有假设：Current hypotheses focus on control by monomer biosynthesis and/or export, while cell wall polymerization is viewed as random and non-limiting. 

主要发现：Here we show that combinations of multiple individual laccases (LACs) are nonredundantly and specifically required to set the lignin chemistry in different cell types and their distinct cell wall layers. 

结果1-LAC高阶突变体：We dissected the roles of Arabidopsis thaliana LAC4, 5, 10, 12 and 17 by generating quadruple and quintuple loss-of-function mutants. Loss of these LACs in different combinations led to specific changes in lignin chemistry affecting both residue ring structures and/or aliphatic tails in specific cell types and cell wall layers.  

结果2-LAC介导的木质化的功能特化：Moreover, we showed that LAC-mediated lignification has distinct functions in specific cell types, waterproofing fibers and strengthening vessels. 

结论：Altogether, we propose that the spatial control of lignin chemistry depends on different combinations of LACs with nonredundant activities immobilized in specific cell types and cell wall layers.

Fig. 5. Histology of higher order lac mutants

Tab. S2. Summary of higher order lacmutants

维管植物利用木质素酚醛聚合物来加固不同木质部细胞类型的细胞壁。不同细胞层和细胞类型之间的木质素化学成分都存在差异，从而满足其特定的功能。然而，控制特定木质素化学成分紧密空间定位的机制仍不清楚。目前的假设多集中于控制木质素单体的生物合成和/或输出，而细胞壁聚合被认为是随机且非限制性的。本文中，作者发现多个漆酶的组合特异性作用于不同细胞类型及其不同细胞壁层中的木质素化学成分，并且功能不冗余。作者通过创制四突和五突解析了拟南芥LAC4/5/10/12/17的功能。不同组合中缺失了这些LACs会导致木质素化学成分的特定改变，影响特定细胞类型和细胞壁层的残基环结构和/或亲脂尾。此外，作者还发现LAC介导的木质化在特定细胞类型中具有不同的功能，即使纤维防水和加固导管。综上，作者认为在特定细胞类型和细胞壁层中的木质素化学成分空间控制，主要依赖于功能非冗余的不同LACs组合。