Q.69 For fusion of protoplast this chemical is used as a fusogen:
l. Potassium Sulphate
2. Chloroform
3. Polyethylene Glycol (PEG)
4. Glycerol
Correct Answer: Option 3 – Polyethylene Glycol (PEG)
Polyethylene Glycol (PEG) is the standard fusogen used in protoplast fusion, inducing membrane destabilization and agglutination for successful cell wall-less plant cell merging in somatic hybridization.
Option Analysis
Each chemical’s role in protoplast fusion is distinct:
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1. Potassium Sulphate: No role in fusion; it’s a fertilizer salt, not a fusogen.
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2. Chloroform: Organic solvent used for DNA extraction, toxic to protoplasts causing lysis, not fusion.
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3. Polyethylene Glycol (PEG): Correct. High molecular weight PEG (MW 6000) neutralizes surface charges, causes protoplast aggregation, membrane fusion; standard in protocols at 15-50% concentration.
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4. Glycerol: Cryoprotectant, stabilizes protoplasts during storage; high concentrations dehydrate but don’t induce fusion like PEG.
Detailed Mechanism
PEG-induced fusion: PEG dehydrates the space between protoplasts, reducing zeta potential (surface charge), leading to tight adhesion → membrane mixing → cytoplasmic/nuclear fusion.
Why PEG is preferred:
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High fusion frequency (20-50%)
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Low toxicity
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Works across plant species
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Used with Ca²⁺ for better results
Introduction to Protoplast Fusion Fusogen
Protoplast fusion creates somatic hybrids by merging plant protoplasts (wall-less cells). The fusogen induces membrane fusion. Polyethylene Glycol (PEG) is the gold standard chemical fusogen in biotechnology, essential for NEET biology preparation.
Why PEG is the Protoplast Fusion Fusogen
PEG mechanism (MW 1500-8000):
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Dehydration: Removes water between protoplasts
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Charge neutralization: Reduces negative surface charge
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Agglutination: Protoplasts stick together
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Membrane fusion: Lipid bilayers merge within minutes
Standard protocol: Mix protoplasts → add 25-35% PEG → incubate 15-30 min → wash → culture.
Other Chemicals Explained
| Chemical | Role | Why NOT fusogen |
|---|---|---|
| Potassium Sulphate | Plant nutrient | No membrane effect |
| Chloroform | DNA extraction solvent | Destroys protoplasts |
| Glycerol | Stabilizer/cryoprotectant | Causes shrinkage, no fusion |
| PEG | Fusogen | Induces fusion ✓ |
Exam Relevance & Applications
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NEET focus: PEG consistently appears in biotech questions
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Real applications: Tomato + potato = Pomato; disease-resistant hybrids
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Alternatives: Electrofusion, but PEG is chemical standard
Memory tip: “PEG fuses protoplasts” – P for Protoplast, E for Effective, G for Gold standard.
Protoplast Fusion Success Factors
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Fresh protoplasts (viability >80%)
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PEG concentration optimization
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Ca²⁺ enhancement
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Proper washing post-fusion
