Why do lepidopterans die when they feed on Bt cotton plant ? Explain how does it happen.

Explanation

Bt cotton plants are the transgenic plants that express a gene called cry gene, found in bacteria.
This gene encodes for protein crystals having insecticidal properties against insects of group Lepidoptera, Diptera and Coleoptera. .Inside the bacterium, these proteins remain inactive and does not harm the bacteria. However, these inactive crystals can get activated in the alkaline pH of the gut of insects upon ingestion.
After activation, these crystals can bind to the receptors present on the membranes of gut epithelial cells. Due to this binding, the membrane swells and pores are created on them. These pores lead to bursting of cell. Hence, soon the lepidopteran dies due to starvation.