Xiao Peng, Pfaff Sarah A, Zhao Wancheng, Debnath Debkumar, Vojvodin Cameron S, Liu Chang-Jun, Cosgrove Daniel J, Wang Tuo
Department of Chemistry, Michigan State University, East Lansing, MI, USA.
Department of Biology, Pennsylvania State University, University Park, PA, USA.
Nat Commun. 2025 Aug 27;16(1):8010. doi: 10.1038/s41467-025-63512-0.
Lignification waterproofs and strengthens secondary plant cell walls but increases the energy cost of sugar release for biofuels. The physical association between lignin and the carbohydrate scaffold that accommodates lignin polymerization, along with the distinct roles of lignin units and carbohydrate partners during lignification, remain unclear. Here, we map lignin-carbohydrate spatial proximity by solid-state NMR in C-labeled Arabidopsis inflorescence stems during secondary cell wall formation. Analyses include wild-type plants and mutants that selectively or globally disrupt lignin biosynthesis. Mature walls in basal regions show enrichment of S-lignin and dense carbohydrate-lignin packing. Acetylated xylan predominantly associates with S-lignin, while methylated pectin unexpectedly interacts with G-lignin during early-stage lignification. The importance of S-lignin in stabilizing the carbohydrate-lignin interface is highlighted by weak lignin-carbohydrate contacts and compromised mechanical properties in the low-S fah1 mutant, whereas the ref3 mutant, despite reduced lignin content, remains unaffected due to a high S/G ratio. Thus, molecular mixing patterns, rather than lignin content, critically determine the structure and properties of lignocellulosic materials.
木质化作用使植物次生细胞壁具有防水性并增强其强度，但会增加生物燃料释放糖分的能量成本。木质素与容纳木质素聚合的碳水化合物支架之间的物理关联，以及木质化过程中木质素单元和碳水化合物伴侣的不同作用仍不清楚。在这里，我们通过固态核磁共振技术绘制了拟南芥花序茎在次生细胞壁形成过程中C标记的木质素 - 碳水化合物空间接近度图谱。分析包括野生型植物以及选择性或全局性破坏木质素生物合成的突变体。基部区域的成熟细胞壁显示出S型木质素的富集以及密集的碳水化合物 - 木质素堆积。乙酰化木聚糖主要与S型木质素结合，而甲基化果胶在木质化早期意外地与G型木质素相互作用。低S型fah1突变体中木质素 - 碳水化合物接触较弱且机械性能受损，突出了S型木质素在稳定碳水化合物 - 木质素界面中的重要性，而ref3突变体尽管木质素含量降低，但由于S/G比值高而不受影响。因此，分子混合模式而非木质素含量，关键地决定了木质纤维素材料的结构和性质。
