question_answer

Biotechnologists identified the source and isolated different types of cry genes from the bacterium Bacillus thuringiensis and incorporated them into many crops. Briefly explain, how have these genes brought beneficial changes in the crops and the mankind?

Answer:

Cry genes (Bt toxin genes) were isolated from the bacterium Bacillus thuringiensis and were incorporated into several crops like cotton, tomato, etc. Some strains of B. thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). B. thuringiensis forms protein crystals during a particular phase of growth which contains a toxic insecticidal protein. This protein encoded by cry gene exists as inactive protoxin, but becomes active on ingestion by an insect. This happens because of the alkaline pH of the gut which solubilises the crystals. This toxin creates pore, cell swelling, lysis and eventually lead to death of the insect. The choice of the Bt toxin genes depends on the crops and targeted pest as most Bt toxins are insect group specific. They have helped in developing insect resistance. Bt toxin gene has been cloned from the bacteria and has been expressed in plants to provide them resistance to the insects without the need for insecticides, e.g. Bt cotton, Bt com, rice, etc.