The extracellular matrix (ECM) of many charophytes, the assemblage of green algae that are the sister group to land plants, is complex, produced in large amounts, and has multiple essential functions. An extensive secretory apparatus and endomembrane system are presumably needed to synthesize and secrete the ECM, but structural details of such a system have not been fully characterized. Penium margaritaceum is a valuable unicellular model charophyte for studying secretion dynamics. We report that Penium has a highly organized endomembrane system, consisting of 150–200 non-mobile Golgi bodies that process and package ECM components into different sets of vesicles that traffic to the cortical cytoplasm, where they are transported around the cell by cytoplasmic streaming. At either fixed or transient areas, specific cytoplasmic vesicles fuse with the plasma membrane and secrete their constituents. Extracellular polysaccharide (EPS) production was observed to occur in one location of the Golgi body and sometimes in unique Golgi hybrids. Treatment of cells with brefeldin A caused disruption of the Golgi body, and inhibition of EPS secretion and cell wall expansion. The structure of the endomembrane system in Penium provides mechanistic insights into how extant charophytes generate large quantities of ECM, which in their ancestors facilitated the colonization of land.

中文翻译：

---

膜的结构和动力学在单细胞的藻类，玛格丽塔菌的细胞外基质的分泌过程中。

许多藻类的胞外基质（ECM）是绿藻的组合，是陆地植物的姊妹群，是复杂的，大量产生的，并具有多种基本功能。为了合成和分泌ECM，可能需要广泛的分泌设备和内膜系统，但是这种系统的结构细节尚未得到充分表征。玛格丽丝青霉菌是一种有价值的用于研究分泌动力学的单细胞模型藻。我们报告Penium有一个高度组织化的内膜系统，该系统由150-200个非移动的高尔基体组成，这些体将ECM成分加工和包装成不同的囊泡集，然后运到皮质细胞质，在此处它们通过细胞质流在细胞周围运输。在固定或短暂区域，特定的细胞质囊泡与质膜融合并分泌其成分。观察到细胞外多糖（EPS）的产生发生在高尔基体的一个位置，有时在独特的高尔基杂交体中发生。用布雷菲德菌素A处理细胞会导致高尔基体破裂，并抑制EPS分泌和细胞壁膨胀。Penium内膜系统的结构 提供有关现存的藻类如何产生大量ECM的机制的见解，这在他们的祖先中促进了土地定殖。