The insecticidal crystalline protein introduced into transgenic crops to provide pest resistance exists as an inactive protoxin in the source bacterium. Which of the following conditions triggers the conversion of this protoxin into its active form once ingested by the target insect?

Step-by-step solution

The insecticidal crystalline protein (Bt toxin) is produced by the bacterium Bacillus thuringiensis as an inactive protoxin. Once an insect ingests the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut, which solubilises the crystals. The active toxin binds to the surface of midgut epithelial cells and creates pores that cause cell swelling and lysis, eventually leading to the death of the insect. Answer: The alkaline pH of the insect's gut