Name the insect pest that is killed by the products of cryIAc gene. Explain how the gene makes the plant resistant to the insect pest

Insect is cotton boll worms.
cryIAc is responsible to produce a toxic crystalline protein known as cry protein (Bt toxin). It is not toxic to the bacterium because it exist as an inactive 
protoxin in the bacterium. When this toxin enters the insect , it is converted into an active form of toxin due to the alkalyne p^H of the gut. 
The activated toxin binds to the surface of midgut epithelial cells and create pores. It causes death of the insect. 

Some more insects of order Lepidoptera(tobacco bud worm; army worm), Coleoptera (beetles),diptera(mosquito; flies)

Meloidegyne incognitia.
The gene produces crystals of insecticidal protein which is inactive protoxin, when the bollworm eats the protoxin, the alkaline pH of the gut activates it. Activated protoxin binds to the midgut epithelial cells, creates pores/ causes swelling/ causes lysis / kills the worm.

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