Question

What are Cry proteins ? How have biotechnologists exploited these proteins to benefit farmers ?

Hint:

Specificity Matters:
{cryIAc} and {cryIIAb} $\rightarrow$ control Cotton Bollworms.
{cryIAb} $\rightarrow$ controls Corn Borer.

Answer 1

Step 1: Understanding the Concept:
Bacillus thuringiensis is a soil bacterium that naturally produces protein crystals during a specific phase of its life cycle. These crystals contain the "Cry" (Crystal) protein.
Step 2: Detailed Explanation:
1. Mechanism of Toxicity:
- The protein is produced as an inactive protoxin in the bacterium (this ensures the bacterium itself isn't killed).
- When an insect (like a bollworm) eats the plant, the protoxin enters its gut.
- The alkaline pH of the insect's midgut solubilizes the crystal and activates the toxin.
- The active toxin binds to the midgut lining, creating pores. This causes cell swelling and lysis, eventually starving and killing the insect.
2. Biotechnological Exploitation:
- Scientists isolated the specific genes (cry genes) from the bacteria.
- They inserted these genes into the DNA of crop plants (e.g., Bt-Cotton, Bt-Corn).
- Now, the plant produces its own pesticide.
3. Benefits to Farmers:
- Reduced dependency on expensive chemical pesticide sprays.
- Protection of beneficial insects that would normally be killed by broad-spectrum sprays.
- Higher crop yields due to reduced pest damage.
Step 3: Final Answer:
Cry proteins are natural biopesticides. By transferring the genes responsible for these proteins into crops, scientists have created plants that can defend themselves against specific insect pests.