School of Biological Sciences, The University of Auckland, Auckland Mail Centre, Private Bag 92019, Auckland, 1142, New Zealand.
Faculty of Health and Environmental Sciences, Institute for Applied Ecology New Zealand, School of Applied Sciences, Auckland University of Technology, Private Bag 92006, Auckland, 1142, New Zealand.
Planta. 2021 Jun 4;254(1):2. doi: 10.1007/s00425-021-03650-z.
Heteromannans are the predominant hemicelluloses in the gametophytic stem of the moss Hypnodendron menziesii and occur in the walls of all cell types Little is known about the cell-wall polysaccharides of mosses. Monosaccharide analysis of cell walls isolated from the stem of the umbrella moss Hypnodendron menziesii was consistent with heteromannans, probably galactoglucomannans, being the predominant hemicellulosic polysaccharides in the walls. Immunofluorescence and immunogold microscopy with the monoclonal antibody LM21, specific for heteromannans, showed that these polysaccharides were present in the walls of all stem cell types. These cell types, except the hydroids, have secondary walls. Experiments in which sections were pre-treated with 0.1 M sodium carbonate and with the enzyme pectate lyase indicated that the heteromannans have O-acetyl groups that limit LM21 binding and the cell walls contain pectic homogalacturonan that masks detection of heteromannans using LM21. Therefore, to fully detect heteromannans in the cell walls, it was essential to use these pre-treatments to remove the O-acetyl groups from the heteromannans and pectic homogalacturonan from the cell walls. Fluorescence microscopy experiments with a second monoclonal antibody, LM22, also specific for heteromannans, showed similar results, but the binding was considerably weaker than with LM21, possibly as a result of subtle structural differences in the epitopes of the two antibodies. Although heteromannans occur abundantly in the cell walls of many species in basal lineages of tracheophytes, prior to the present study, research on the distribution of these polysaccharides in the walls of different cell types in mosses was confined to the model species Physcomitrium patens.
杂甘露聚糖是伞藻 Hypnodendron menziesii 配子体茎中的主要半纤维素，存在于所有细胞类型的细胞壁中。关于苔藓细胞壁多糖知之甚少。从伞藻 Hypnodendron menziesii 茎中分离出的细胞壁的单糖分析与杂甘露聚糖一致，可能是半乳糖葡甘露聚糖，是细胞壁中主要的半纤维素多糖。用特异性识别杂甘露聚糖的单克隆抗体 LM21 进行免疫荧光和免疫金显微镜观察表明，这些多糖存在于所有茎细胞类型的细胞壁中。这些细胞类型，除了水螅体，都有次生壁。在切片用 0.1 M 碳酸钠和果胶裂解酶预处理的实验中表明，杂甘露聚糖具有 O-乙酰基，限制了 LM21 的结合，细胞壁中含有果胶同质半乳糖醛酸聚糖，掩盖了使用 LM21 检测杂甘露聚糖。因此，要充分检测细胞壁中的杂甘露聚糖，必须使用这些预处理方法去除杂甘露聚糖上的 O-乙酰基和细胞壁中的果胶同质半乳糖醛酸聚糖。用另一种特异性识别杂甘露聚糖的单克隆抗体 LM22 进行荧光显微镜实验也得到了类似的结果，但与 LM21 相比，结合强度要弱得多，这可能是由于两种抗体的抗原决定簇存在细微结构差异。尽管杂甘露聚糖在许多维管植物基群的细胞壁中大量存在，但在本研究之前，关于这些多糖在不同细胞类型细胞壁中分布的研究仅限于模式物种 Physcomitrium patens。
