Q.Bacillus thuringiensis is widely used as a biopesticide. Describe how it kills insect larvae once ingested, and name one crop plant that has been genetically engineered to express its toxin gene.
Bacillus thuringiensis produces protein crystals, commonly called Cry proteins or Bt toxin, that are toxic specifically to the larvae of susceptible insects such as certain moths, butterflies and beetles. When Bt spores and crystals are sprayed onto a crop as a biopesticide and subsequently ingested by a feeding larva, the crystal protein is activated within the insect's alkaline gut environment, where it binds to specific receptors on the gut lining. This binding damages the gut wall, ultimately killing the insect. Because Cry proteins bind only to receptors present in the guts of particular target insect groups, Bt is highly selective, largely sparing humans, other mammals, birds, and beneficial insects such as bees. This selectivity has made the Bt toxin gene a widely used tool in agricultural genetic engineering: the gene has been isolated and introduced into the genome of cotton, producing genetically engineered Bt cotton varieties capable of producing the insecticidal protein themselves.
[!ANSWER] Ingested Bt crystal toxin is activated in an insect's alkaline gut, damaging the gut lining and killing the larva; cotton has been genetically engineered (Bt cotton) to express this toxin gene directly.
Unlock everything free for 14 days
- Full step-by-step solutions
- Concept-first explanations
- Methods, shortcuts & mistakes
- PYQ mapping + timed mock tests
Full access for 14 days. No credit card required.