Question

The Bt toxin is used for killing nematodes in crop plant. But, it is non-toxic to human. Select the correct reason for this

• A. the pro Bt toxin activation requires temperature above human body temperature
• B. the Bt toxin recognises only insect specific target
• C. the Bt toxin formation from pro Bt toxin requires pH lower than that present in human stomach
• D. conversion of pro Bt toxin to Bt toxin takes place only in highly alkaline conditions

Answer 1

Answer: (D)

The $Bt$ toxin protein exist as inactive proctoreins, but once an insects ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals. The activated toxin binds to the surface of midgut epithelial cells and create pores that causes cell swelling and lysis and eventically cause death of the insect.