protoplast

A protoplast is a cell whose cell wall has been removed, leaving the plasma membrane and the cell’s internal organelles intact. In plants, fungi, and bacteria, protoplasts are produced by enzymatic digestion or other methods that remove the cell wall while maintaining osmotic stability to prevent rupture. Plant protoplasts are typically isolated from leaf tissue or suspension cultures using enzymes such as cellulase, hemicellulase, and pectinase in isotonic solutions. Bacterial and fungal protoplasts are generated with lysozyme or other lytic enzymes, usually in the presence of osmotic stabilizers.

In plant biology, protoplasts are widely used for studies of cell wall formation, membrane transport, and intracellular processes, as well as for genetic engineering and somatic hybridization. Protoplasts can be transformed to take up DNA through methods such as polyethylene glycol-mediated uptake or electroporation, enabling gene function studies and the creation of transgenic lines. Protoplast fusion allows the combining of genetic material from different species or varieties to produce somatic hybrids for breeding.

Regeneration is a key feature of plant protoplasts: under appropriate hormonal conditions, they synthesize a new cell wall, divide to form microcolonies, and can regenerate into callus tissue or whole plants. The success of regeneration depends on species, tissue source, and culture conditions, particularly the balance of auxins and cytokinins and the osmotic environment during initial culture.

Terminology varies by organism. Protoplasts typically refer to wall-less plant or fungal cells, while in bacteria, spheroplasts are more commonly used for cells with partially removed walls or altered outer membranes; usage can differ among laboratories.