Question

An application of biotechnology in agriculture involves the production of pest-resistant plants, using "cry" gene from a bacterium, \textit{Bacillus thuringiensis.} (a) Proteins coded by which specific Bt. toxin gene control corn borer? (b) How does Bt. toxin produced by the bacterium kill the insect? Explain.

Hint:

The Cry proteins from \textit{Bacillus thuringiensis} act as insecticides by forming pores in the insect's gut, leading to cell damage, digestive failure, and eventually the death of the pest.

Answer 1

(a) Proteins coded by which specific Bt. toxin gene control corn borer?
- The specific Bt. toxin gene that controls corn borer is the cry1Ab gene.
- The cry genes in \textit{Bacillus thuringiensis} code for proteins called Cry proteins (insecticidal proteins). The Cry1Ab protein is toxic to the larvae of the corn borer (\textit{Ostrinia nubilalis}).
(b) How does Bt. toxin produced by the bacterium kill the insect? Explain.
- The Cry protein produced by \textit{Bacillus thuringiensis} is ingested by the larvae of the corn borer when they feed on the Bt. cotton or Bt. corn.
- Once ingested, the Cry protein is activated in the insect's alkaline digestive system. The protein binds to specific receptors in the insect's gut cells, forming pores in the gut lining.
- These pores cause the gut cells to break down, leading to the loss of the gut's permeability, disrupting digestion. This results in the death of the insect due to starvation and septicemia.