Vanholme Bartel, Vanholme Ruben, Turumtay Halbay, Goeminne Geert, Cesarino Igor, Goubet Florence, Morreel Kris, Rencoret Jorge, Bulone Vincent, Hooijmaijers Cortwa, De Rycke Riet, Gheysen Godelieve, Ralph John, De Block Marc, Meulewaeter Frank, Boerjan Wout
Department of Plant Systems Biology, Flanders Institute for Biotechnology, 9052 Ghent, Belgium.
Plant Physiol. 2014 May;165(1):290-308. doi: 10.1104/pp.113.233742. Epub 2014 Mar 24.
To study the effect of short N-acetylglucosamine (GlcNAc) oligosaccharides on the physiology of plants, N-ACETYLGLUCOSAMINYLTRANSFERASE (NodC) of Azorhizobium caulinodans was expressed in Arabidopsis (Arabidopsis thaliana). The corresponding enzyme catalyzes the polymerization of GlcNAc and, accordingly, β-1,4-GlcNAc oligomers accumulated in the plant. A phenotype characterized by difficulties in developing an inflorescence stem was visible when plants were grown for several weeks under short-day conditions before transfer to long-day conditions. In addition, a positive correlation between the oligomer concentration and the penetrance of the phenotype was demonstrated. Although NodC overexpression lines produced less cell wall compared with wild-type plants under nonpermissive conditions, no indications were found for changes in the amount of the major cell wall polymers. The effect on the cell wall was reflected at the transcriptome level. In addition to genes encoding cell wall-modifying enzymes, a whole set of genes encoding membrane-coupled receptor-like kinases were differentially expressed upon GlcNAc accumulation, many of which encoded proteins with an extracellular Domain of Unknown Function26. Although stress-related genes were also differentially expressed, the observed response differed from that of a classical chitin response. This is in line with the fact that the produced chitin oligomers were too small to activate the chitin receptor-mediated signal cascade. Based on our observations, we propose a model in which the oligosaccharides modify the architecture of the cell wall by acting as competitors in carbohydrate-carbohydrate or carbohydrate-protein interactions, thereby affecting noncovalent interactions in the cell wall or at the interface between the cell wall and the plasma membrane.
为了研究短链N - 乙酰葡糖胺（GlcNAc）寡糖对植物生理的影响，将茎瘤固氮根瘤菌的N - 乙酰葡糖胺基转移酶（NodC）在拟南芥（Arabidopsis thaliana）中表达。相应的酶催化GlcNAc的聚合，因此，β-1,4 - GlcNAc寡聚物在植物中积累。当植物在短日条件下生长数周后转移到长日条件下时，可见一种以花序茎发育困难为特征的表型。此外，还证明了寡聚物浓度与表型的外显率之间存在正相关。尽管在非允许条件下，NodC过表达系产生的细胞壁比野生型植物少，但未发现主要细胞壁聚合物含量有变化的迹象。对细胞壁的影响在转录组水平上得到反映。除了编码细胞壁修饰酶的基因外，一组编码膜偶联受体样激酶的基因在GlcNAc积累时差异表达，其中许多编码具有未知功能的26细胞外结构域的蛋白质。尽管与胁迫相关的基因也差异表达，但观察到的反应与经典几丁质反应不同。这与所产生的几丁质寡聚物太小而无法激活几丁质受体介导的信号级联反应这一事实是一致的。基于我们的观察结果，我们提出了一个模型，其中寡糖通过在碳水化合物 - 碳水化合物或碳水化合物 - 蛋白质相互作用中作为竞争者来修饰细胞壁的结构，从而影响细胞壁中或细胞壁与质膜界面处的非共价相互作用。
