Question

When an insect feeds on the Bt plant, the insect dies due to the conversion of inactive protein to active protein in:

• A. Alkaline pH of the gut.
• B. Acidic pH of the gut.
• C. Acidic pH of saliva.
• D. Alkaline pH of saliva.

Answer 1

The Correct Option is A

Activation in the Alkaline pH of the Gut

When an insect feeds on a Bt plant, the insect dies due to the conversion of an inactive protein to an active toxin in the alkaline pH of the gut.

Process of Toxin Activation

• Ingestion of Crystal Proteins: The insect ingests the Bt plant material, which contains the inactive form of the Cry protein (crystal protein).
• Activation in the Gut: The inactive Cry protein is activated in the alkaline environment of the insect’s gut (pH 9.0 to 10.5), where it is solubilized and proteolytically processed into an active toxin.
• Binding and Pore Formation: The active toxin binds to specific receptors on the midgut epithelial cells of the insect, forming pores that disrupt the cell membrane.
• Cell Lysis and Death: The formation of these pores leads to cell lysis, leakage of the midgut contents, and ultimately, the death of the insect.

Specificity and Safety

This mechanism ensures that the toxin is only activated in the specific conditions of the insect’s gut, making it highly specific to target insects while being safe for humans and other animals with acidic digestive tracts.

Conclusion

The activation of Bt toxins in the alkaline pH of the insect gut is a critical step in the mechanism of action. This specificity allows Bt crops to effectively control pest populations while minimizing environmental impact and ensuring safety for non-target organisms.