In Bt cotton, the Bt toxin present in plant tissue as pro-toxin is converted into active toxin due to

Options

A. Alkaline pH of the insect gut
B. Acidic pH of the insect gut
C. Action of gut microorganisms
D. Presence of conversion factors in insect gut

Answer

**Step-by-Step Solution:**

1. **Understanding Bt Cotton**: Bt cotton is a genetically modified organism (GMO) that has been engineered to express a protein from the bacterium *Bacillus thuringiensis* (Bt). This protein is known for its insecticidal properties.

2. **Role of Bt Toxin**: The toxin produced by *Bacillus thuringiensis* is initially in an inactive form known as a protoxin. This protoxin is not harmful to the plant or the bacterium itself.

3. **Activation of Protoxin**: When insects consume the Bt cotton, the protoxin enters the insect's gut. The environment in the gut is crucial for the conversion of protoxin to its active form.

4. **pH of Insect Gut**: The key factor that activates the protoxin is the pH level in the insect's gut. In this case, the gut has an alkaline (basic) pH.

5. **Conversion Process**: The alkaline pH causes the protoxin to solubilize and undergo a conformational change, converting it into the active toxin. This active toxin can then bind to the gut cells of the insect.

6. **Mechanism of Action**: Once activated, the toxin creates pores in the gut cells, leading to cell swelling and ultimately cell lysis, which results in the death of the insect.

7. **Conclusion**: Therefore, the conversion of the Bt toxin from protoxin to active toxin in Bt cotton occurs due to the alkaline pH of the insect gut.

**Final Answer**: The correct option is A) alkaline pH of the insect gut.

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