The below mentioned article provides the mechanism of protoplast fusion with six explanations.
The mechanism of protoplast fusion is not fully known. Several explanations have been put forward to understand the mechanism of protoplast fusion.
Some important explanations are given below:
1. When the protoplasts are brought into close proximity, this is followed by an induction phase whereby changes induced in electrostatic potential of the membrane result in fusion. After fusion, the membrane stabilizes and the surface potential returns to their former state.
2. When the protoplasts are closely adhered, the external fusogens cause disturbance in the intra-membranous proteins and glycoproteins. This increases membrane fluidity and creates a region where lipid molecule intermix, allowing coalescence of adjacent membranes.
3. The negative charge carried by protoplasts is mainly due to intra-membranous phosphate groups. The addition of Ca2+ ions causes the zeta-potential of plasma membrane to be reduced and under that condition the protoplasts aggregate.
4. The high alkaline solution used in chemo-fusion induces the intra-membranous production of lysophospholipid which may be linked with membranous fusion.
5. The high molecular weight (1,000-6,000)/polymer of PEG acts as a molecular bridge connecting the protoplasts and Ca2+ ions link the negatively charged PEG and membrane surface. On elution of the PEG, the surface potential are disturbed, leading to inter-membrane contact and subsequent fusion. Besides this, the strong affinity of PEG for water may cause local dehydration of the membrane and increase fluidity, thus inducing fusion.
6. PEG itself induces aggregation, but α-tocopherol present as an impurity in commercial grade PEG, actually promotes membrane fusion.