f Structural differences between two types of basidiomycete septal pore caps
- Authors: Wally H. Müller, Roy C. Montijn, Bruno M. Humbel, Adriaan C. van Aelst, Eline J. M. C. Boon, Theo P. van der Krift, Teun Boekhout
- Author for correspondence: Wally H. Müller (Department of Molecular Cell Biology). Tel: + 31 30 2533449. Fax: + 31 30 2513655.
- First Published Online: 01 July 1998, Microbiology 144: 1721-1730, doi: 10.1099/00221287-144-7-1721
- Subject: Development And Structure
- Issue Published:
The septal pore cap (SPC) of Trichosporon sporotrichoides CBS 8245 is vesicular-tubular, connected with flat-tubular endoplasmic reticulum (ER), and stains densely with zinc/iodine/osmium tetroxide, as does the ER. The SPC of Schizophyllum commune CBS 340.81 is more complex, about 600 nm in diameter, with perforations of 80--120 nm diameter, and stains less densely with zinc/iodine/osmium tetroxide than the ER. In high-pressure frozen and freeze-substituted hyphae of T. sporotrichoides the ER is present parallel to the dolipore septa, and electron-dense material occurs opposite the septal pore channel; the SPC rarely showed smooth vesicular-tubular membranes, suggesting that this is an ephemeral function of the SPC. The SPC of S. commune has a smooth outer and inner membrane, which enclose a matrix with a palisade-like substructure. A thin layer of electron-dense material covers the inner surface of the SPC of S. commune, from which beaded filamentous structures connect the SPC and the pore-occluding material. These filamentous structures may maintain the intracellular position of the SPC and possibly play a role in plugging the septal pore channel. The septal pore swellings of T. sporotrichoides contain more 1,6--glucan than the septum, and intracellular glucans are also present near the septal pore channel. This cytosolic 1,6--glucan in T. sporotrichoides may serve as a matrix to keep the tubular membranous structures of the SPC together. In contrast, 1,6--glucan is not observed in the SPC and in the pore-occluding material of S. commune, and hyphal septa of this species show less labelling of 1,6--glucan than the septal swelling. The evolutionary transition from simple to more complex types of SPCs may have resulted in a requirement for different components to maintain the morphological integrity and cell biological function.
- Keyword(s): septal pore cap, Schizophyllum commune, high-pressure freezing, Trichosporon sporotrichoides, 1,6--glucan
© Society for General Microbiology 1998 | Published by the Microbiology Society
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