Peng Xiao-Peng, Bian Jing, Yao Shuang-Quan, Ma Cheng-Ye, Wen Jia-Long
State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of Tree Breeding and Cultivation of the National Forestry and Grassland Administration, Research Institute of Forestry, Chinese Academy of Forestry, Beijing, China.
Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, China.
Front Bioeng Biotechnol. 2021 Nov 15;9:790539. doi: 10.3389/fbioe.2021.790539. eCollection 2021.
Elucidating the chemical and structural characteristics of hemicelluloses and lignin in the -coumarate 3-hydroxylase (C3H) down-regulated poplar wood will be beneficial to the upstream gene validation and downstream biomass conversion of this kind of transgenic poplar. Herein, the representative hemicelluloses and lignin with unaltered structures were prepared from control (CK) and C3H down-regulated 84K poplars. Modern analytical techniques, such as C NMR, 2D-HSQC NMR, and gel chromatography (GPC), were performed to better delineate the structural changes of hemicelluloses and lignin caused by transgenesis. Results showed that both the hemicelluloses (H and H) extracted from control and C3H down-regulated poplar wood have a chain backbone of (1→4)-β-D-Xylan with 4--Me-α-D-GlcpA as side chain, and the branch degree of the H is higher than that of H. With regarding to the lignin macromolecules, NMR results demonstrated that the syringyl/guaiacyl (S/G) ratio and dominant substructure β--4 linkages in C3H down-regulated poplar were lower than those of control poplar wood. By contrast, native lignin from C3H down-regulated poplar wood exhibited higher contents of -hydroxybenzoate (PB) and -hydroxyphenyl (H) units. In short, C3H down-regulation resulted in the chemical and structural changes of the hemicelluloses and lignin in these poplar wood. The identified structures will facilitate the downstream utilization and applications of lignocellulosic materials in the biorefinery strategy. Furthermore, this study could provide some illuminating results for genetic breeding on the improvement of wood properties and efficient utilization of poplar wood.
阐明对香豆酸3 - 羟化酶（C3H）下调的杨树木材中半纤维素和木质素的化学和结构特征，将有助于此类转基因杨树的上游基因验证和下游生物质转化。在此，从对照（CK）和C3H下调的84K杨树中制备了结构未改变的代表性半纤维素和木质素。采用现代分析技术，如碳核磁共振（C NMR）、二维异核单量子相干核磁共振（2D - HSQC NMR）和凝胶色谱（GPC），以更好地描绘转基因引起的半纤维素和木质素的结构变化。结果表明，从对照和C3H下调的杨树木材中提取的半纤维素（H和H）均具有以（1→4）-β - D - 木聚糖为主链、4 - O - 甲基 - α - D - 葡萄糖醛酸为侧链的结构，且H的支化度高于H。关于木质素大分子，核磁共振结果表明，C3H下调的杨树中紫丁香基/愈创木基（S/G）比率和主要亚结构β - O - 4键低于对照杨树木材。相比之下，C3H下调的杨树木材中的天然木质素表现出较高含量的对羟基苯甲酸酯（PB）和对羟基苯基（H）单元。简而言之，C3H下调导致了这些杨树木材中半纤维素和木质素的化学和结构变化。所确定的结构将有助于木质纤维素材料在生物炼制策略中的下游利用和应用。此外，本研究可为杨树木材性质改良和高效利用的遗传育种提供一些有启发性的结果。
