Protoplasts

J. Spiral and co-workers, "Protoplast Culture and Regeneration in Coffea Species," in Ref. 40. 

Protoplast ciAture.s. Cellular tissues devoid of cell wall material in culture... 

Gilroy, S., Hughes, W. A., and Trewavas, A. J. (1989). A comparison between Quin-2 and aequorin as indicators of cytoplasmic calcium levels in higher plant cell protoplasts. Plant Physiol. 90 482—491. 

Wiest, S.C. Steponkus, P.L. (1978). Freeze-thaw injury to isolated spinach protoplasts and its simulabon at above freezing temperatures. Plant Physiol. 62,699-705. 

Kaiser, W.M. (1982). Correlation between changes in photosynthetic activity and changes in total protoplast volume in leaf tissue from hygro-, meso-, and xer-ophytes under osmotic stress. Planta, 154, 538-45. 

The drying protoplast will be subjected to tension as the result of volume contraction and its adherence to the cell wall. Early observations (Steinbrick, 1900) on desiccation tolerant species showed that the protoplasm does not separate from the wall, but rather that it folds and cavities develop in the wall. Where there are thick-walled cells, localised separation of the plasmalemma from the wall may occur. It seems unlikely, however, that rupture of the plasmalemma normally occurs during desiccation. A more subtle form of membrane damage may arise from dehydration-induced conformational changes. Certainly it is relatively easy to demonstrate that dehydrated membranes exhibit a loss of functional integrity... 

One of the exciting features of the direct DNA delivery system is that it does not rely on an infection. The limited host range of other vector delivery systems is therefore irrelevant, and the way is opened for genetic engineering of cereals. Cereal protoplasts are equally amenable to uptake of foreign DNA after electroporation and the system therefore has potential for use with the major crop species. However, there is at present one drawback, namely that for cereals it has not yet proved possible to grow fertile whole plants from the genetically transformed cells. 

Plant tissue and protoplast culture applications to stress physiology and biochemistry... 

The use of protoplasts in studies of stress physiology and biochemistry expands the advantages of cell culture systems discussed in the preceding sections. Additional applications are related to the fusion of protoplasts. Intraspecifie and interspecific protoplast fusion greatly enhance genetic variability of the fused protoplasts (Kumar Cocking, 1987). The resulting somatic hybrids provide cells which can be used for selection of specific traits (e.g. environmental stress tolerance) provided by one or both donor cells and for basic studies on cytoplasmic and nuclear inheritance of desired characteristics. 

Refinement of techniques involved in protoplast isolation has enhaneed the success of isolation of vaeuoles and other intracellular structures... 

The literature is less extensive on the use of protoplasts in stress-tolerance investigations however, some applications have been attempted. For example, in one study protoplasts were isolated from the leaves of a wild relative of tomato shown to be salt tolerant and from a salt-sensitive, cultivated species (Rosen Tal, 1981). In the presence of NaCI the plating efficiency (number of surviving cells/number of cells applied to the plate) of the wild relative was greater than the cultivated, sensitive cultivar. Proline, when added to the culture media, was found to enhance the plating efficiency of the salt-sensitive cultivar but not the wild, salt-tolerant relative. These results suggest that traits related to salt tolerance are expressed by the isolated protoplasts and that the response of protoplasts to environmental stress can be manipulated, i.e. the proline response. 

A more significant body of literature focuses on the use of protoplasts in understanding processes related to stress tolerance. The role of Ca in salt toleranee has been evaluated using maize root protoplasts. Exposure of the plasmalemma directly to external media revealed a non-specific replacement of Ca by salt. Sodium was found to replace Ca though this could be reversed by adding more Ca (Lynch, Cramer Lauchli, 1987). This approach assists in understanding the role of specific ion interaction in enhancing salt tolerance and is potentially applicable to studies on the molecular basis for ion specificity of plant membranes. 

Abdullah, R., Cocking, E.C. Thompson, J.A. (1986). Efficient plant regeneration from rice protoplasts through somatic embryogenesis. Biol Technology, 4, 1087-90. 

Alibert, G., Bondet, A.M., Canut, H. Rataboul, P. (1985). Protoplasts in studies of vacuolar storage compounds. In The Physiological Properties of Plant Protoplasts, ed. P.E. Pilte, pp. 105-15. Berlin Springer. 

Harrison, B.D. Mayo, M.A. (1983). The use of protoplasts in plant virus research. In Use of Tissue Culture and Protoplasts in Plant Pathology, ed. J.P. Hegelson and B.J. Deverall, pp. 69-129. New York Academic Press. 

Imbrie-Milligan, C.W. Hodges, T.K. (1986). Microcallus formation from maize protoplasts prepared from embryogenic callus. Planta, 168, 395-401. 

Kumar, A. Cocking, E.C. (1987). Protoplast fusion A novel approach to organelle genetics in higher plants. American Journal of Botany, 74, 1289-303. 

Lin, W., Odell, J.T. Schreiner, R.M. (1987). Soybean protoplast culture and direct gene uptake and expression by cultured soybean protoplasts. Plant Physiology, 84, 856 1. 

Lynch, J., Cramer, G.R. Lauchli, A. (1987). Salinity reduces membrane-associated calcium in corn root protoplasts. Plant Physiology, 83, 390-4. 

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