Department of Biology, University of Wisconsin-Stevens Point, Stevens Point, WI, USA.
Ann Bot. 2022 Sep 26;130(4):595-609. doi: 10.1093/aob/mcac096.
Intervessel pit membranes (PMs) are important cell wall structures in the vessel system that may impact a plant's water transport and its susceptibility to vascular diseases. Functional roles of intervessel PMs largely depend on their structure and polysaccharide composition, which are the targets of this study.
With grapevine used as a model plant, this study applied an immunogold-scanning electron microscopy technique to simultaneously analyse at high resolution intervessel PM structures and major pectic and hemicellulosic polysaccharides that make up intervessel PMs.
Intervessel PMs in functional xylem showed significant structural variation, with about 90 % of them being structurally intact with smooth or relatively smooth surfaces and the remaining 10 % with progressively degraded structures. The results also elucidated details of the removal process of cell wall materials from the intervessel PM surface toward its depth during its natural degradation. Four groups of pectic and hemicellulosic polysaccharides were immunolocalized in intervessel PMs and differed in their spatial distribution and abundance. Weakly methyl-esterified homogalacturonans (WMe-HGs, detected by JIM5) were abundant in the surface layer, heavily methyl-esterified homogalacturonans (HMe-HGs, detected by JIM7) and xylans detected by CCRC-M140 were mostly found in deeper layers, and fucosylated xyloglucans (F-XyGs, detected by CCRC-M1) were more uniformly distributed at different depths of the intervessel PM.
Intervessel PMs displayed diverse structural variations in grapevine. They contained certain major groups of pectic and hemicellulosic polysaccharides with different spatial distributions and abundance. This information is crucial to reveal the polysaccharide profiling of the primary cell wall and to understand the roles of intervessel PMs in the regulation of water transport as well as in a plant's susceptibility to vascular diseases.
脉间 pit 膜（PM）是维管束系统中的重要细胞壁结构，可能影响植物的水分运输及其对血管疾病的易感性。PM 的功能主要取决于其结构和多糖组成，这是本研究的目标。
以葡萄为模型植物，本研究采用免疫金扫描电子显微镜技术，同时分析维管束 PM 结构和构成 PM 的主要果胶和半纤维素多糖，以高分辨率进行分析。
功能木质部的脉间 PM 表现出明显的结构变异，其中约 90%的结构完整，表面光滑或相对光滑，其余 10%的结构逐渐降解。结果还阐明了在其自然降解过程中，细胞壁材料从 PM 表面向其深处去除的详细过程。在脉间 PM 中免疫定位了 4 组果胶和半纤维素多糖，它们在空间分布和丰度上存在差异。弱甲基酯化半乳糖醛酸聚糖（WMe-HGs，由 JIM5 检测）在表面层丰富，高度甲基酯化半乳糖醛酸聚糖（HMe-HGs，由 JIM7 检测）和木聚糖（由 CCRC-M140 检测）主要存在于更深的层，而岩藻糖基木葡聚糖（F-XyGs，由 CCRC-M1 检测）在 PM 的不同深度均匀分布。
葡萄的脉间 PM 表现出多种结构变异。它们含有某些主要的果胶和半纤维素多糖组，具有不同的空间分布和丰度。这些信息对于揭示初生细胞壁的多糖特征以及理解 PM 在调节水分运输以及植物对血管疾病的易感性方面的作用至关重要。
