The protoplasts have considerably attracted biotechnologists attension despite several technical difficulties and are now either being utilized in several areas of academic as well as applied interests or thought to be used in different aspects in future. Some of the most important applications of isolated protoplasts, for instance are as follows:
The first report of plant regeneration from isolated protoplast in Nicotiana tabacum was published in 1971 by Takeba et al. Since then, scientists throughout the globe are engaged in regenerating new plants directly from isolated protoplasts: Successful plant regeneration have been achieved for a wide range of cultivars and breeding lines of potato of US and European origin. In addition, plants have also regenerated from several other species of Solanum. The latter include 5. brevidens, S. phureja, S. etuberosu and S. penelliti.
Two reports of plant regeneration from proloplasts of temperate fruit trees are encouraging. First, Ochatt and Cane (1986) have regenerated plants from mesophyll protoplast of wild pear, Pyrus communis var pyraster C. and second Ochatt et al (1987) have successfully regenerated whole plant from mesophyll protoplast of the cold cherry (Prunus sp). This marks the first report of plant regeneration from protoplast of a temperate fruit tree of significant commercial value.
Improvement of cereals by protoplast culture technique still waits development of reproducible methods of plant regeneration because, at present, the culture of cereal protoplasts faces extreme difficulties.
However, true regeneration, from a cereal protoplast culture has been reported in Pennisetum americanum. Protoplast from an embryo-derived suspension culture were able to proceed all the way to an intact plant. But, it is not yet confirmed whether this phenomenon will turn out to be generally for all cereals.
Cell Wall Biosynthesis:
The cultured protoplasts rapidly regenerate new cell wall, and thus they offer a novel system for the study of wall biosynthesis and deposition.
Protoplasts in Plant Physiology:
When growth promoters like indole acetic acid (IAA) are applied to plants, they act directly on plasma membrane of the cell and increase the permeability of the membrane to water thus enabling the cell to elongate. This phenomenon can be established using protoplasts in vitro when IAA is applied to the plasmolyticum containing protoplasts the latter expands rapidly and finally burst due to too much vacuolation. Further, it can be verified by applying antiauxins that suppress this bursting, indicating that the site of action of IAA is the plasma membrane of the plant cell. Similarly, the action-site of 'Paraquat' can also be established. This herbicide disrupts plasma membrane and enables protoplast bursting.
Introduction of "Foreign " Material : The protoplasts, because of being wallless, show high pinocytic activity and can ingest biologically active 'foreign' materials such as macromolecules like ferritin and polystyrene latex particles, nuclei, chloroplasts, mitochondria, DNA, plasmids, bacteria, viruses etc. in their cytoplasm by a process similar to endocytosis as described for certain animal cells and protozoans.
Carlson claimed to have achieved uptake of chloroplasts by protoplast, uptake of isolated nuclei of Petunia by mesophyll protoplasts of Petuma, tobacco and maize was reported by Potrykus and Hoffmann (1973) Davey and Cocking (1972) and Davey (1977) demonstrated that isolated mesophyll protoplasts of leguminous plants could take up the cells of Rhizobium.
However, the ingestion of "foreign" materials results in modified cells after cell wall regeneration. These procedures may be more advantageous to a plant breeder in getting more efficient crop varieties in near future.
Plant Virus Interrelationships:
The plant virus interrelationships in the part were not clearly known due to lack of suitable experimental systems. This problem has come to an end as a result of the innovation of protoplast isolation and its culture. Protoplasts can directly be inoculated with pathogenic virus and their effects can be studied extensively with relative care.
Use of Protoplast-Populations as Single Cellular Systems:
One of the exciting and potential properties of protoplasts that each isolated protoplast is entirely separated from another and thus corresponds to microorganisms. In this way, a population of protoplasts provides the best possible approach to a single isolated cell system and can be used to study the selection of mutant cell lines, cloning of cell populations and the synchronous infection of protoplasts by virus.
Protoplast and Biochemical Studies:
Isolated plant protoplasts have opened vistas for certain biochemical studies.