Abstract
Plasmodesmata or intercellular bridges that connect plant cells are cylindrical channels approximately 40 nm in diameter. Running through the center of each is a dense rod, the desmotubule, that is connected to the endoplasmic reticulum of adjacent cells. Fern, Onoclea sensibilis, gametophytes were cut in half and the cut surfaces exposed to the detergent, Triton X 100, then fixed. Although the plasma membrane limiting the plasmodesma is solubilized partially or completely, the desmotubule remains intact. Alternatively, if the cut surface is exposed to papain, then fixed, the desmotubule disappears, but the plasma membrane limiting the plasmodesmata remains intact albeit swollen and irregular in profile. Gametophytes were plasmolyzed, and then fixed. As the cells retract from their cell walls they leave behind the plasmodesmata still inserted in the cell wall. They can break cleanly when the cell proper retracts or can pull away portions of the plasma membrane of the cell with them. Where the desmotubule remains intact, the plasmodesma retains its shape. These images and the results with detergents and proteases indicate that the desmotubule provides a cytoskeletal element for each plasmodesma, an element that not only stabilizes the whole structure, but also limits its size and porosity. It is likely to be composed in large part of protein. Suggestions are made as to why this structure has been selected for in evolution.
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Selected References
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- Baron-Epel O., Hernandez D., Jiang L. W., Meiners S., Schindler M. Dynamic continuity of cytoplasmic and membrane compartments between plant cells. J Cell Biol. 1988 Mar;106(3):715–721. doi: 10.1083/jcb.106.3.715. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Deom C. M., Oliver M. J., Beachy R. N. The 30-kilodalton gene product of tobacco mosaic virus potentiates virus movement. Science. 1987 Jul 24;237(4813):389–394. doi: 10.1126/science.237.4813.389. [DOI] [PubMed] [Google Scholar]
- Hertzberg E. L., Lawrence T. S., Gilula N. B. Gap junctional communication. Annu Rev Physiol. 1981;43:479–491. doi: 10.1146/annurev.ph.43.030181.002403. [DOI] [PubMed] [Google Scholar]
- Kitajima E. W., Lauritis J. A. Plant virions in plasmodesmata. Virology. 1969 Apr;37(4):681–685. doi: 10.1016/0042-6822(69)90288-8. [DOI] [PubMed] [Google Scholar]
- Spurr A. R. A low-viscosity epoxy resin embedding medium for electron microscopy. J Ultrastruct Res. 1969 Jan;26(1):31–43. doi: 10.1016/s0022-5320(69)90033-1. [DOI] [PubMed] [Google Scholar]
- Wolf S., Deom C. M., Beachy R. N., Lucas W. J. Movement protein of tobacco mosaic virus modifies plasmodesmatal size exclusion limit. Science. 1989 Oct 20;246(4928):377–379. doi: 10.1126/science.246.4928.377. [DOI] [PubMed] [Google Scholar]