Question

Write a short note on Pest Resistant Plant.

Hint:

Bt cotton = cry gene from Bacillus thuringiensis making the plant toxic only to certain insects.

Answer 1

Step 1: Concept:
Pest-resistant plants are genetically modified (transgenic) crop plants that have been engineered to resist attack by insect pests, reducing the need for chemical insecticide sprays.

Step 2: Example — Bt cotton:
The best-known example is Bt cotton, which carries a gene (cry gene) from the soil bacterium Bacillus thuringiensis. This gene codes for a crystal (Bt toxin) protein that is toxic specifically to certain insect larvae, such as the cotton bollworm.

Step 3: Mode of action:
The Bt toxin remains inactive in the plant until it is ingested by a susceptible insect. In the insect's alkaline gut, the toxin is activated and binds to specific receptors on the midgut epithelial cells, creating pores that cause cell lysis and death of the insect, while remaining harmless to humans because our acidic gut and different receptors do not activate or bind the toxin.

Final Answer:
Pest-resistant plants like Bt cotton use a bacterial toxin gene to kill specific insect pests while remaining safe for humans and non-target organisms.