da Silva Roberta Maidana, Dos Santos Rinaldo Pires, Mastroberti Alexandra Antunes
Postgraduate Program in Botany, Institute of Biosciences, Federal University of Rio Grande Do Sul, Porto Alegre, RS, Brazil.
Department of Botany, Institute of Biosciences, Federal University of Rio Grande Do Sul, Porto Alegre, RS, Brazil.
Protoplasma. 2025 Jun 4. doi: 10.1007/s00709-025-02080-y.
Mucilage cells have critical ecological and functional importance, including water storage, transport, and seed protection. These cells can exhibit diverse morphologies, often accompanied by structural changes in the cell wall, which are key to their functionality. In Myrsine umbellata, epidermal mucilage cells exhibit dual secretion: phenolic compounds and mucilage. These contents are separated by a "cell wall"; however, the formation and composition of this wall after cell differentiation remain unclear. Although some studies suggest the presence of an inner cell wall, its development and chemical makeup have not been thoroughly investigated. Using immunocytochemistry and transmission electron microscopy, we found that the new wall forms continuously with the innermost layer of the outer periclinal wall. This new layer resembles primary walls in composition, containing high levels of homogalacturonans (HGs) with a high degree of methyl-esterification, and rhamnogalacturonan I (RG-I) with arabinan side chains. It also includes low concentrations of de-esterified HGs bound to calcium ions and RG-I with galactan side chains. In the mature stage, the new wall also contains higher concentrations of arabinogalactan proteins (AGPs) and cellulose. This newly formed wall compartmentalizes the mucilage cell, isolating the protoplast from the mucilaginous compartment, thus preserving the protoplast and preventing cell death in this idioblast.
黏液细胞具有至关重要的生态和功能意义，包括水分储存、运输和种子保护。这些细胞可呈现出多样的形态，通常伴随着细胞壁的结构变化，而这些变化是其功能的关键所在。在伞花铁仔中，表皮黏液细胞表现出双重分泌：酚类化合物和黏液。这些成分由一层“细胞壁”分隔；然而，细胞分化后该壁的形成和组成仍不清楚。尽管一些研究表明存在内层细胞壁，但其发育和化学组成尚未得到充分研究。通过免疫细胞化学和透射电子显微镜，我们发现新壁与外层周壁的最内层连续形成。这一新层在组成上类似于初生壁，含有高水平的高度甲基酯化的同型半乳糖醛酸聚糖（HGs）以及带有阿拉伯糖侧链的鼠李半乳糖醛酸聚糖I（RG-I）。它还包括低浓度的与钙离子结合的去酯化HGs以及带有半乳聚糖侧链的RG-I。在成熟阶段，新壁还含有更高浓度的阿拉伯半乳聚糖蛋白（AGPs）和纤维素。这一新形成的壁将黏液细胞分隔开来，将原生质体与黏液区室隔离开，从而保护原生质体并防止该异细胞死亡。
