Question

What are cry-proteins? Name an organism that produces it. How has man exploited this protein to his benefit?

Answer 1

Hint: Cry proteins are the insecticidal protein secreted as crystalline endotoxin by Bacillus thuringiensis. These proteins are encoded by a cry gene which is toxic to certain insects.

Complete answer:
Cry proteins are produced by Bacillus thuringiensis. During sporulation, it forms intracellular crystalline bodies that contain an insecticidal protein called endotoxin. The endotoxin that accumulates in the bacterium is an inactive precursor. After ingestion by the insect, this protoxin is cleaved by proteases (alkaline conditions in gut), resulting in shorter versions of the protein which displays toxic activity by binding in the midgut and damaging the surface epithelium by creating pores that causes swelling and lysis of the insect.
The toxin called Bt-toxin is produced by bacillus thuringiensis has been cloned in bacteria and expressed in plants to provide resistance to insects.
Examples are Bt cotton, corn, rice, tomato, potato and soybean. Specific Bt toxin genes were isolated from bacillus thuringiensis and inserted into the several crop plants such as cotton.
Humans are taking advantage by inserting BT toxin genes in the several plant crops to produce transgenic crops to increase the yield and quality of crops and these crops are insect resistant.

Note: These cry proteins are effective against various types of insects e.g., Lepidopterans (tobacco budworm), coleopterans (beetles). There are a number of such genes, the proteins encoded by gene cry1Ac and cry2Ab controls corn borer and cotton bollworm.