Pharmaceutical Institute, Department of Pharmaceutical Biology, Christian-Albrechts-University of Kiel, Gutenbergstr. 76, 24118, Kiel, Germany.
Laboratory of Food Chemistry, Wageningen University & Research, Bornse Weilanden 9, 6708 WG, Wageningen, The Netherlands.
BMC Plant Biol. 2022 Feb 4;22(1):63. doi: 10.1186/s12870-022-03447-6.
The polyphyletic group of seagrasses shows an evolutionary history from early monocotyledonous land plants to the marine environment. Seagrasses form important coastal ecosystems worldwide and large amounts of seagrass detritus washed on beaches might also be valuable bioeconomical resources. Despite this importance and potential, little is known about adaptation of these angiosperms to the marine environment and their cell walls.
We investigated polysaccharide composition of nine seagrass species from the Mediterranean, Red Sea and eastern Indian Ocean. Sequential extraction revealed a similar seagrass cell wall polysaccharide composition to terrestrial angiosperms: arabinogalactans, pectins and different hemicelluloses, especially xylans and/or xyloglucans. However, the pectic fractions were characterized by the monosaccharide apiose, suggesting unusual apiogalacturonans are a common feature of seagrass cell walls. Detailed analyses of four representative species identified differences between organs and species in their constituent monosaccharide composition and lignin content and structure. Rhizomes were richer in glucosyl units compared to leaves and roots. Enhalus had high apiosyl and arabinosyl abundance, while two Australian species of Amphibolis and Posidonia, were characterized by high amounts of xylosyl residues. Interestingly, the latter two species contained appreciable amounts of lignin, especially in roots and rhizomes whereas Zostera and Enhalus were lignin-free. Lignin structure in Amphibolis was characterized by a higher syringyl content compared to that of Posidonia.
Our investigations give a first comprehensive overview on cell wall composition across seagrass families, which will help understanding adaptation to a marine environment in the evolutionary context and evaluating the potential of seagrass in biorefinery incentives.
多系的海草群从早期的单子叶陆生植物进化到海洋环境。海草形成了全球重要的沿海生态系统，大量冲上海滩的海草碎屑也可能是有价值的生物经济资源。尽管如此重要且具有潜力，但人们对这些被子植物适应海洋环境及其细胞壁的了解甚少。
我们研究了来自地中海、红海和东印度洋的 9 种海草的多糖组成。顺序提取揭示了与陆生被子植物相似的海草细胞壁多糖组成：阿拉伯半乳聚糖、果胶和不同的半纤维素，特别是木聚糖和/或木葡聚糖。然而，果胶部分的特征单糖是芹糖，这表明不寻常的-apiogalacturonans 是海草细胞壁的一个共同特征。对四种代表性物种的详细分析确定了器官之间以及物种之间在组成单糖组成和木质素含量和结构方面的差异。根茎中葡萄糖基单元的含量比叶片和根丰富。Enhalus 含有丰富的阿比糖基和阿拉伯糖基，而两种澳大利亚的 Amphibolis 和 Posidonia 物种以大量的木糖基残基为特征。有趣的是，后两个物种含有相当数量的木质素，特别是在根和根茎中，而 Zostera 和 Enhalus 则不含木质素。与 Posidonia 相比，Amphibolis 木质素结构的丁香基含量较高。
我们的研究首次全面概述了海草科细胞壁的组成，这将有助于从进化的角度了解对海洋环境的适应，并评估海草在生物炼制激励措施中的潜力。
