Read the passage and answer the following questions :

Genetic modification (GM) has been utilized to create custom-designed plants that serve as alternative resources for industries, producing starches, fuels, and pharmaceuticals. Biotechnology in agriculture has numerous applications, one of which involves developing pest-resistant plants to reduce the reliance on chemical pesticides. This is achieved by introducing the Bt toxin gene from the bacterium Bacillus thuringiensis (Bt) into plants, creating what is known as a bio-pesticide. Notable examples include Bt cotton, Bt corn, rice, tomato, potato, and soybean.Bt toxin is a naturally occurring insecticidal protein produced by certain strains of Bacillus thuringiensis. During a specific phase of their growth, these bacteria form protein crystals containing toxic substances. These crystals harbor inactive protoxins, which, when activated, become lethal to targeted insects. Different Bt toxin genes, such as cryIAc and cryIIAb, have been isolated and introduced into various crop plants, depending on the crop and the specific pests targeted, as Bt toxins are often insect-group specific. By incorporating these genes, plants gain inherent resistance to insects without the need for synthetic insecticides. This advancement in biotechnology has significant implications for sustainable and eco-friendly agricultural practices.

Which of the following is responsible for activation of protoxin to active Bt toxin of the Bacillus thuringiensis in boll worm.

Alkaline pH of the gut .

The correct answer is Option (3) - Alkaline pH of gut.

Bacillus thuringiensis (Bt) is a bacterium that produces proteins called Bt toxins, which are toxic to certain insects. These toxins have been utilized in biotechnology to create pest-resistant plants, reducing the need for chemical insecticides. One such example is Bt cotton, where the Bt toxin gene is cloned from the bacterium and expressed in the plant.

Some strains of Bacillus thuringiensis produce proteins that kill certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes).

The Bt toxins are produced in the form of protein crystals during a specific phase of B. thuringiensis growth. These crystals contain an inactive form of the toxin, known as protoxins. Interestingly, the toxin does not harm the bacterium itself because the toxin is in its inactive form.

When an insect ingests the inactive toxin, it reaches the alkaline environment of the insect's gut. The alkaline pH of the gut solubilizes the crystals, converting the protoxins into their active toxin form. The activated toxin then binds to the surface of the midgut epithelial cells of the insect. Once bound, the toxin creates pores in the cell membrane, causing the cells to swell and eventually lyse (burst). This disruption in the midgut epithelium leads to the insect's death.