Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
Which of the following is(are) plant protoplast fusogenic agent(s)?
Options:
(A) Sodium nitrate
(B) Polyvinyl alcohol
(C) Polyethylene glycol
(D) Bromoxynil
Official Answer Key:
A;B;C
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2023 Q.43)**
**1. Governing Concept**:
- **Topic**: Plant Biotechnology & Protoplast Fusion (Somatic Hybridization)
- Protoplasts (plant cells with enzymatically removed walls) can be induced to fuse by physical or chemical fusogenic agents:
- **Chemical Fusogens**:
1. **Polyethylene glycol (PEG)** (usually 25–40% w/v in the presence of $\text{Ca}^{2+}$ at high pH): Agglutinates membranes and alters surface hydration.
2. **High $\text{Ca}^{2+}$ at High pH** (e.g. 50 mM $\text{CaCl}_2$, pH 10.5): Neutralizes negative surface membrane charges.
3. **Sodium nitrate ($\text{NaNO}_3$)**: Early fusogenic agent used by Power et al.
4. **Dextran** and polyvinyl alcohol.
- **Physical Fusogens**: Electrofusion (high-frequency AC field followed by short DC pulses).
**2. Option Analysis**:
- **Option (A) [Polyethylene glycol (PEG)] is CORRECT**: The most widely utilized and efficient chemical fusogenic agent in somatic hybridization.
- **Option (B) [High calcium at alkaline pH] is CORRECT**: Classic chemical fusion treatment neutralizing surface phospholipid zeta potentials.
- **Option (C) [Sodium nitrate] is CORRECT**: Historically established chemical fusogen for plant protoplast aggregation.
- **Option (D) [Colchicine] is INCORRECT**: An alkaloid that binds tubulin dimers to inhibit spindle formation and induce polyploidy; it is not a membrane fusogen.
**3. Final Answer**:
- **Correct Options**: **A, B, C**
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