The inactive protoxin is activated in the gut of the insect by :

Options

A. acidic pH
B. alkaline pH
C. low temperature
D. high temperature

Answer

B

Explanation

Bacillus thuringinensis forms a protein crystal (Cry ) during a particular phase of their growth. These crystals contains a toxic insecticidal protein.
Bt toxin protein exists as an inactive protoxins, but once it ingests the inactive toxin, it is converted to the active form due to the alkaline pH of the gut which helps in solubilisation of these crystals.
The activated toxin then binds to the surface of midgut epithelial cells, creating pores that causes cell swelling and lysis which leads to the death of the insects.