Enigmatic apiogalacturonans: Investigations on structure, taxonomic occurrence, localization and responses to environmental factors will help disentangling this unusual group of pectic polysaccharides

神秘的apiogalacturonans：对结构、分类发生、定位和对环境因素的反应的研究将有助于解开这一不寻常的果胶多糖组

• 批准号: 527586818
• 负责人: Dr. Lukas Pfeifer
• 金额: --
• 依托单位: Abteilung Pharmazeutische Biologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/527586818?language=en
• 关键词: Enigmatic; apiogalacturonans; Investigations; structure; taxonomic

Polysaccharides are major components of the plant cell wall. Some of them, namely the pectins, possess a very complicated and highly charged structure. Among the pectic polysaccharides, one subgroup, the apiogalacturonans (AGAs), are only rarely described throughout the whole green lineage. Up to now, AGAs are only known from duckweeds and seagrasses. Both groups are neither monophyletic nor closely related, but belong to the order of Alismatales. This fact pinpoints a shared evolutionary trajectory and highlights the need of a systematized analysis throughout that order to infer influence factors, which lead to AGAs occurrence. In a first step, representative members of the order will be investigated for AGA presence and structure by extraction from the crude pectin fraction. Size-exclusion chromatography as well as specific enzymatic cleavages (usage of a recently described rhamnogalacturonan-I lyase) will help to purify the apiosylated homogalacturonan scaffold named AGA. As available structural data on the few structurally described AGAs (from duckweeds and seagrasses) are contradictory to some extent, a detailed analysis of structural features will be performed by classical polysaccharide analysis methodologies. Plant species of different lifestyles and habitats (freshwater, brackish water, saline water and terrestrial) are included to represent most possible triggering factors for AGA biosynthesis. Duckweeds accumulate high amounts of boron and boron is usually crosslinked by apiose residues in rhamnogalacturonan-II. Therefore, an experimental set-up with Lemna in-vitro culture and Zostera callus culture will be used to correlate influences of boron (determined by ICP-MS) on AGA content. The hypothesis of a boron-storage function of AGAs and influences of salinity on the degree of AGA expression will be tested. Monoclonal antibodies are an important tool for plant cell wall research. They help to investigate the localization and presence of polysaccharide epitopes in plantae. The purified AGAs of Zostera will be used as antigen to immunize mice and generate a monoclonal antibody directed against the apiose side chain structures. This antibody will provide a valuable tool to foster the research on AGA localization by immunofluorescence as well as transmission electron microscopy and will complement the available antibody toolkit against pectic epitopes. In conclusion, the proposed project on AGAs will help to expand the current knowledge on this unusual group of pectic polysaccharides in various ways. This research will hint towards a molecular understanding of the stimulating factors leading to AGAs’ occurrence pattern in land plants.

多糖是植物细胞壁的主要成分。它们中的一些，即果胶，具有非常复杂和高度带电的结构。在果胶多糖中，一个亚组，apiogalacturonans（AGA），在整个绿色谱系中很少描述。到目前为止，AGA仅从浮萍和海草中发现。这两个组既不是单系的，也不是密切相关的，但属于泽泻目。这一事实指出了一个共同的进化轨迹，并强调了在整个顺序中进行系统化分析的必要性，以推断导致AGA发生的影响因素。在第一步中，将通过从粗果胶级分中提取来研究该目的代表性成员的阿加存在和结构。尺寸排阻色谱法以及特异性酶裂解（使用最近描述的鼠李糖半乳糖醛酸聚糖-I裂解酶）将有助于纯化名为阿加的无糖基化同型半乳糖醛酸聚糖支架。由于现有的几个结构描述的AGA（来自浮萍和海草）的结构数据在一定程度上是矛盾的，将通过经典的多糖分析方法进行结构特征的详细分析。不同的生活方式和栖息地（淡水，半咸水，咸水和陆地）的植物物种包括代表最可能的触发因素阿加生物合成。浮萍积累了大量的硼，硼通常被鼠李糖半乳糖醛酸-II中的芹菜糖残基交联。因此，将使用浮萍体外培养和大叶藻愈伤组织培养的实验装置来关联硼（通过ICP-MS测定）对阿加含量的影响。AGA的硼储存功能和盐度对阿加表达程度的影响的假设将被检验。单克隆抗体是研究植物细胞壁的重要工具。它们有助于研究植物中多糖表位的定位和存在。将纯化的大叶藻AGA作为抗原免疫小鼠并产生针对芹菜糖侧链结构的单克隆抗体。这种抗体将提供一个有价值的工具，以促进阿加定位的免疫荧光以及透射电子显微镜的研究，并将补充现有的抗体工具包对果胶表位。总之，拟议的AGA项目将有助于以各种方式扩大对这一不寻常的果胶多糖组的现有知识。本研究将有助于从分子水平上了解陆生植物中AGA发生的刺激因素。