The structure of plasmodesmata as revealed by plasmolysis, detergent extraction, and protease digestion.

Abstract

Abstract. Plasmodesmata or intercellular bridges that connect plant ceils are cylindrical channels •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 ceils. 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.

Plasmolysis: new insights into an old process

“…8). By contrast, Tilney et al (1991) suggested that when the protoplast shrinks away from the wall, the desmotubule readily breaks its connection with the ER, and they did not find elements of ER attached to the desmotubule. Thus, the connection of the desmotubule to the ER may be weak in comparison with the connection between the desmotubule and the PM lining the pore.…”

“…Thus, both PM and desmotubule appear to be strongly anchored within plasmodesmata. Indeed, Tilney et al (1991) have suggested that the desmotubule miay function as a cytoskeletal element, stabilizing the plasmodesmata and giving rise to plasmodesmata of fixed pore sizes.…”

“…In a recent study, Tilney et al (1991) examined the effects of a range of treatments, including plasmolysis, on plasmodesmata in fern gametophytes. They found that the plasmodesmata remained embedded in the wall, although rarely they appeared to be pulled completely out, leaving a hole in the wall.…”

Different uptake pathways between hydrophilic and hydrophobic compounds in lateral roots of <i>Cucurbita pepo</i>

“…4) In addition, symplastic diffusion via plasmodesmata could decrease because of disconnection by plasmolysis. 23) Thus, our plasmolyzed root results suggest that plasmolysis disrupts the function of the endodermal Casparian strip to regulate diffusion (but does not break the structure).…”

Bacterial Detoxification of Copper and Its Impacts on Germination Indices of Barley and Mung Bean

“…After entering the cells, the non-ionic Cu particles are able to transport between cells via plasmodesmata which are microscopic channels of plants traversing the cell walls and enabling transport and communication between cells. Plasmodesmata or intercellular bridges were reported to be cylindrical channels with 40nm in diameter (Tilney et al, 1991). These plasmodesmata allow particles to pass from cell to another depending on their size causing less toxic effects than ionic Cu.…”