Abstract 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.
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Endosidin 5 disruption of the Golgi apparatus and extracellular matrix secretion in the unicellular charophyte Penium margaritaceum
Endosidins are a group of low-molecular-weight compounds, first identified by ‘chemical biology’ screening assays, that have been used to target specific components of the endomembrane system. In this study, we employed multiple microscopy-based screening techniques to elucidate the effects of endosidin 5 (ES5) on the Golgi apparatus and the secretion of extracellular matrix (ECM) components in Penium margaritaceum. These effects were compared with those caused by treatments with brefeldin A and concanamycin A. Penium margaritaceum’s extensive Golgi apparatus and endomembrane system make it an outstanding model organism for screening changes to the endomembrane system. Here we detail changes to the Golgi apparatus and secretion of ECM material caused by ES5.
Changes to extracellular polymeric substance (EPS) secretion and cell wall expansion were screened using fluorescence microscopy. Confocal laser scanning microscopy and transmission electron microscopy were used to assess changes to the Golgi apparatus, the cell wall and the vesicular network. Electron tomography was also performed to detail the changes to the Golgi apparatus.
While other endosidins were able to impact EPS secretion and cell wall expansion, only ES5 completely inhibited EPS secretion and cell wall expansion over 24 h. Short treatments of ES5 resulted in displacement of the Golgi bodies from their typical linear alignment. The number of cisternae decreased per Golgi stack and trans face cisternae in-curled to form distinct elongate circular profiles. Longer treatment resulted in a transformation of the Golgi body to an irregular aggregate of cisternae. These alterations could be reversed by removal of ES5 and returning cells to culture.
ES5 alters secretion of ECM material in Penium by affecting the Golgi apparatus and does so in a markedly different way from other endomembrane inhibitors such as brefeldin A and concanamycin A.
- Award ID(s):
- 2129443
- NSF-PAR ID:
- 10430583
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Annals of Botany
- Volume:
- 131
- Issue:
- 6
- ISSN:
- 0305-7364
- Format(s):
- Medium: X Size: p. 967-983
- Size(s):
- ["p. 967-983"]
- Sponsoring Org:
- National Science Foundation
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