Bt toxin protects the cotton plants against insect pests by causing
Bt toxin protects the cotton plants against insect pests by causing
The correct option is A swelling and lysis of midgut of the insect
The genes responsible for the production of Bt toxin, commonly called cry genes, are present in a bacterium called Bacillus thuringiensis. These genes code for crystalline and insoluble protoxins (inactivated toxins) known as Cry proteins at a particular stage of growth of the bacteria. Specific genes produce specific protein variants that have insecticidal properties against specific group of insects.
Spores of B. thuringiensis are often used as biopesticides for this property. Alternatively, the cry genes are genetically engineered into the genome of cotton plants to form transgenic Bt cotton crops which are resistant to insects pests of the order Lepidoptera.
When the insects or pests feed on the transgenic cotton plants or plants sprayed with the B.thuringiensis spores, they ingest the protoxin molecules. The protoxin is activated in the alkaline pH of their midgut and becomes a soluble toxin protein. The soluble toxin proteins bind to the surface of midgut epithelial cells and create pores there. It is followed by swelling and lysis of the midgut cells due to inflow of water through the pores. The insect stops eating at this point and undergoes starvation. The pores also allow normal gut bacteria of the insect to invade and cause infection. Eventually these events cause the death of the insect.
Since pores are created only in midgut epithelial cells, hence, the cells present in the other parts of the body do not undergo swelling. Thus the entire body does not swell up.
Bt toxin does not impair the jointed appendages of insects (arthropods) or their circulatory system. Hence, these are not affected directly.
The genes responsible for the production of Bt toxin, commonly called cry genes, are present in a bacterium called Bacillus thuringiensis. These genes code for crystalline and insoluble protoxins (inactivated toxins) known as Cry proteins at a particular stage of growth of the bacteria. Specific genes produce specific protein variants that have insecticidal properties against specific group of insects.
Spores of B. thuringiensis are often used as biopesticides for this property. Alternatively, the cry genes are genetically engineered into the genome of cotton plants to form transgenic Bt cotton crops which are resistant to insects pests of the order Lepidoptera.
When the insects or pests feed on the transgenic cotton plants or plants sprayed with the B.thuringiensis spores, they ingest the protoxin molecules. The protoxin is activated in the alkaline pH of their midgut and becomes a soluble toxin protein. The soluble toxin proteins bind to the surface of midgut epithelial cells and create pores there. It is followed by swelling and lysis of the midgut cells due to inflow of water through the pores. The insect stops eating at this point and undergoes starvation. The pores also allow normal gut bacteria of the insect to invade and cause infection. Eventually these events cause the death of the insect.
Since pores are created only in midgut epithelial cells, hence, the cells present in the other parts of the body do not undergo swelling. Thus the entire body does not swell up.
Bt toxin does not impair the jointed appendages of insects (arthropods) or their circulatory system. Hence, these are not affected directly.
