Question

An application of biotechnology in agriculture involves the production of pest resistant plants, using “cry” gene from a bacterium, Bacillus thuringiensis.

1. Proteins coded by which specific Bt. toxin gene control corn borer?
2. How does Bt. toxin produced by the bacterium kill the insect? Explain.

Answer 1

1. The cryIAb gene encodes proteins that control corn borer, while cryIAc and cryIIAb control cotton bollworms.
2. The Bt toxin produced by the bacterium Bacillus thuringiensis kills insects through the following mechanism: The bacterium produces an inactive protoxin (crystal protein) during sporulation. When an insect ingests the Bt toxin, it reaches the gut, where the alkaline pH activates the toxin. The activated toxin binds to receptors on the surface of midgut epithelial cells, creating pores. These pores disrupt the midgut epithelium, leading to paralysis, and eventually, the insect stops feeding and dies within 2-3 days.