Coomey Joshua H, Sibout Richard, Hazen Samuel P
Biology Department, University of Massachusetts, Amherst, MA, 01003, USA.
Plant Biology Graduate Program, University of Massachusetts, Amherst, MA, 01003, USA.
New Phytol. 2020 Sep;227(6):1649-1667. doi: 10.1111/nph.16603. Epub 2020 Jun 7.
A key aspect of plant growth is the synthesis and deposition of cell walls. In specific tissues and cell types including xylem and fibre, a thick secondary wall comprised of cellulose, hemicellulose and lignin is deposited. Secondary cell walls provide a physical barrier that protects plants from pathogens, promotes tolerance to abiotic stresses and fortifies cells to withstand the forces associated with water transport and the physical weight of plant structures. Grasses have numerous cell wall features that are distinct from eudicots and other plants. Study of the model species Brachypodium distachyon as well as other grasses has revealed numerous features of the grass cell wall. These include the characterisation of xylosyl and arabinosyltransferases, a mixed-linkage glucan synthase and hydroxycinnamate acyltransferases. Perhaps the most fertile area for discovery has been the formation of lignins, including the identification of novel substrates and enzyme activities towards the synthesis of monolignols. Other enzymes function as polymerising agents or transferases that modify lignins and facilitate interactions with polysaccharides. The regulatory aspects of cell wall biosynthesis are largely overlapping with those of eudicots, but salient differences among species have been resolved that begin to identify the determinants that define grass cell walls.
植物生长的一个关键方面是细胞壁的合成与沉积。在包括木质部和纤维在内的特定组织和细胞类型中，会沉积一层由纤维素、半纤维素和木质素组成的厚次生壁。次生细胞壁提供了一种物理屏障，可保护植物免受病原体侵害，增强对非生物胁迫的耐受性，并强化细胞以承受与水分运输和植物结构物理重量相关的力量。禾本科植物具有许多与双子叶植物和其他植物不同的细胞壁特征。对模式物种短柄草以及其他禾本科植物的研究揭示了禾本科植物细胞壁的众多特征。这些特征包括木糖基转移酶和阿拉伯糖基转移酶、混合连接葡聚糖合酶以及羟基肉桂酸酰基转移酶的特性。也许最具发现潜力的领域是木质素的形成，包括鉴定新的底物和参与单木质醇合成的酶活性。其他酶作为聚合剂或转移酶发挥作用，可修饰木质素并促进其与多糖的相互作用。细胞壁生物合成的调控方面在很大程度上与双子叶植物重叠，但已解决了物种间的显著差异，这些差异开始确定定义禾本科植物细胞壁的决定因素。
