LandWall: Understanding the remodelling and recruitment of internal and external hemicelluloses in the cell walls of land-conquering Zygnematophyceae and the liverwort Marchantia

LandWall：了解征服土地的 Zygnematophyceae 和地钱 Marchantia 细胞壁中内部和外部半纤维素的重塑和补充

• 批准号: 528114108
• 负责人: Dr. Klaus Herburger, Ph.D.
• 金额: --
• 依托单位: Institut für Biowissenschaften (IfBi)
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/528114108?language=en
• 关键词: LandWall; Understanding; remodelling; recruitment; internal

The cells of most green algae and land plants are surrounded by a primary cell wall, which is a load bearing yet extendable matrix composed of various polysaccharides and protects algae from environmental stress such as wate scarcity. A major fraction of these cell wall polysaccharides are hemicelluloses, which can be enzymatically cut and re-connected to another hemicellulose molecules nearby. Such reactions are catalysed by cell wall-bound transglycanases, which occur abundantly in both the Zygnematophyceae and their sister lineage, the land plants. Interestingly, transglycanases are less abundant in early diverging Charophytes (e.g. Klebsormidiophyceae) and Chlorophyta. Hemicellulose transglycosylation is considered to play a key role in the cell wall metabolism of uprightly growing land plants, however, its functions in algae are elusive, even though gene families encoding the responsible enzymes strongly expanded in land-conquering algae, suggesting that they have played important roles in preparing algae and their cell walls for terrestrialization. Moreover, the major substrate of transglycanses and most abundant hemicellulose in land plants – xyloglucan – evolved in Zygnematophyceae. Our recent data indicate that these algae can secrete xyloglucan and other hemicelluloses in surprisingly large amounts into the environment and – vice versa – recruit external polysaccharides back into their cell walls via transglycosylation. We believe that this unexplored hemicellulose secretion and recruitment of polysaccharides helped algae to produce biocrusts that most likely served as their primary habitats during terrestrialization and can be still found worldwide in harsh environments. In order to explore the role of polysaccharide secretion and recruitment, we will devise a series of cultivation experiments and analyses the external polysaccharide footprint of Zygnema and Mesotaenium grown on different substates by state-of-the-art glycobiology techniques. We will compare the secretion pattern with the basal land plant Marchantia, which is known to release xyloglucan from rhizoids. This will be complemented by evaluation compositional and ultrastructural consequences for the cell wall and by tracking polysaccharide secretion and recruitment on a cellular level using new in vivo click chemistry-based imaging approaches. Tracking will consider cross-species exchange of polysaccharides. Finally, transcriptomic changes of relevant carbohydrate-active enzymes will be monitored in response to different external polysaccharides and desiccation stress. We anticipate that our in-depth investigation of polysaccharide remodelling and recruitment will provide novel insights into the role of the cell wall during terrestrialization.

大多数绿藻和陆地植物的细胞被初生细胞壁包围，初生细胞壁是由各种多糖组成的承重且可延伸的基质，可保护藻类免受水资源短缺等环境压力的影响。这些细胞壁多糖的主要部分是半纤维素。 ，它可以被酶切并重新连接到附近的另一个半纤维素分子，这种反应是由细胞壁结合的转聚糖酶催化的。在双藻纲及其姐妹谱系和陆地植物中，转聚糖酶在早期潜水轮藻纲（例如克雷伯索藻纲）和绿藻纲中含量较低，被认为在直立生长的陆地植物的细胞壁代谢中发挥着关键作用。然而，它在藻类中的功能是难以捉摸的，尽管编码相关酶的基因家族已大大扩展此外，陆地植物中转聚糖和最丰富的半纤维素的主要底物——木葡聚糖——是在双藻纲中进化的。藻类可以将木葡聚糖和其他半纤维素以惊人的数量分泌到环境中，反之亦然 - 吸收外部物质我们相信，这种未经探索的半纤维素分泌和多糖的补充有助于藻类产生生物结皮，这些结皮很可能是它们在陆地化过程中的主要栖息地，并且在世界各地的恶劣环境中仍然存在。为了了解多糖分泌和募集的作用，我们将设计一系列培养实验并分析 Zygnema 和 Zygnema 的外部多糖足迹我们将通过最先进的糖生物学技术在不同的基质上生长的 Mesotaenium 的分泌模式与已知从根茎中释放木葡聚糖的基础陆地植物进行比较，这将通过评估其组成和超微结构结果来补充。细胞壁并通过使用新的基于体内点击化学的成像方法在细胞水平上跟踪多糖分泌和募集，跟踪将考虑多糖的跨物种交换。最后，将监测相关碳水化合物活性酶对不同外部多糖和干燥应激的转录组变化，我们预计对多糖重塑和募集的深入研究将为细胞壁在陆地化过程中的作用提供新的见解。