Patten Ann M, Jourdes Michaël, Cardenas Claudia L, Laskar Dhrubojyoti D, Nakazawa Yoshihisa, Chung Byung-Yeoup, Franceschi Vincent R, Davin Laurence B, Lewis Norman G
The Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
Mol Biosyst. 2010 Mar;6(3):499-515. doi: 10.1039/b819206e. Epub 2009 Dec 10.
The interest in renewable, plant-derived, bioenergy/biofuels has resulted in a renaissance of plant cell-wall/lignin research. Herein, effects of modulating lignin monomeric compositions in a single plant species, Arabidopsis, are described. The earliest stage of putative "AcBr/Klason lignin" deposition was apparently unaffected by modulating p-coumarate 3-hydroxylase or ferulate 5-hydroxylase activities. This finding helps account for the inability of many other studies to fully suppress the reported putative levels of lignin deposition through monolignol biosynthesis manipulation, and also underscores limitations in frequently used lignin analytical protocols. The overall putative lignin content was greatly reduced (circa 62%) in a plant line harboring an H-(p-hydroxyphenyl) enriched lignin phenotype. This slightly increased H-monomer deposition level apparently occurred in cell-wall domains normally harboring guaiacyl (G) and/or syringyl (S) lignin moieties. For G- and S-enriched lignin phenotypes, the overall lignification process appeared analogous to wild type, with only xylem fiber and interfascicular fiber cells forming the S-enriched lignins. Laser microscope dissection of vascular bundles and interfascicular fibers, followed by pyrolysis GC/MS, supported these findings. Some cell types, presumably metaxylem and possibly protoxylem, also afforded small amounts of benzodioxane (sub)structures due to limited substrate degeneracy (i.e. utilizing 5-hydroxyconiferyl alcohol rather than sinapyl alcohol). For all plant lines studied, the 8-O-4' inter-unit frequency of cleavable H, G and/or S monomers was essentially invariant of monomeric composition for a given (putative) lignin content. These data again underscore the need for determination of lignin primary structures and identification of all proteins/enzymes involved in control of lignin polymer assembly/macromolecular configuration.
对可再生的、植物源生物能源/生物燃料的关注引发了植物细胞壁/木质素研究的复兴。本文描述了在单一植物物种拟南芥中调节木质素单体组成的影响。推测的“酸不溶/克拉森木质素”沉积的最早阶段显然不受对香豆酸3-羟化酶或阿魏酸5-羟化酶活性调节的影响。这一发现有助于解释许多其他研究为何无法通过单木质醇生物合成操作完全抑制报道的推测木质素沉积水平，也凸显了常用木质素分析方法的局限性。在具有富含H-（对羟基苯基）木质素表型的植物株系中，推测的总木质素含量大幅降低（约62%）。这种H-单体沉积水平略有增加的情况显然发生在通常含有愈创木基（G）和/或紫丁香基（S）木质素部分的细胞壁区域。对于富含G和S的木质素表型，整体木质化过程似乎与野生型相似，只有木质部纤维和束间纤维细胞形成富含S的木质素。对维管束和束间纤维进行激光显微镜解剖，然后进行热解气相色谱/质谱分析，支持了这些发现。一些细胞类型，可能是后生木质部，也可能是原生木质部，由于底物简并性有限（即利用5-羟基松柏醇而非芥子醇），也产生少量苯并二恶烷（亚）结构。对于所有研究的植物株系，对于给定的（推测的）木质素含量，可裂解的H、G和/或S单体的8-O-4'单元间频率基本上与单体组成无关。这些数据再次强调了确定木质素一级结构以及鉴定所有参与控制木质素聚合物组装/大分子构型的蛋白质/酶的必要性。
