Protoplast
From Wikipedia, the free encyclopedia
Protoplast, from the ancient Greek πρώτον (first) + verb πλάθω or πλάττω (to mould: deriv. plastic), initially referred to the first organized body of a species. This meaning is similar to the non-biological definition, the first from which all subsequent forms are derived.
Subsequently it has several biological definitions:
- A protoplast is a plant, bacterial or fungal cell that has had its cell wall completely or partially removed using either mechanical or enzymatic means.
- Protoplasts - Have their cell wall entirely removed
- Spheroplasts - Have their cell wall only partially removed
- More generally protoplast refers to that unit of biology which is composed of a cell's nucleus and the surrounding protoplasmic materials.
[edit] Enzymes for the preparation of protoplasts
Cell walls are made of a variety of polysaccharides. Protoplasts can be made by degrading cell walls with a mixture of the appropriate polysaccharide degrading enzymes:
| Type of cell | Enzyme |
|---|---|
| Plant cells | Cellulase, pectinase, xylanase |
| Gram-positive bacteria | Lysozyme (+EDTA) |
| Fungal cells | Chitinase |
During and subsequent to digestion of the cell wall, the protoplast becomes very sensitive to osmotic stress. This means cell wall digestion and protoplast storage must be done in an isotonic solution to prevent rupture of the plasma membrane.
[edit] Uses for protoplasts
Protoplast can be used to study membrane biology, including the uptake of macromolecules and viruses.
Protoplasts are widely used for DNA transformation (for making genetically modified organisms), since the cell wall would otherwise block the passage of DNA into the cell. Protoplasts may be regenerated into whole plants using micropropagation, a modern technique employing plant tissue culture methods.
Protoplasts may also be used for plant breeding, using a technique called protoplast fusion. Protoplasts from different species are induced to fuse by using an electric field or a solution of polyethylene glycol. This technique may be used to generate hybrids in tissue culture.
