With the help of an example, explain how Bacillus thuringiensis has helped in developing pest resistance in crops.

Pest resistance plants are applications of biotechnology in agriculture.

These pest resistance plants decrease the amount of pesticide used.

Bacillus thuringiensis bacterium is produced from Bt toxin, by cloning Bt toxin. This is then introduced in plants for pest resistance. By making the plant pest resistance there is no need for insecticides to be provided to the plants. Pest resistance plants are like Bt cotton, Bt corn, Bt rice, Bt tomato, etc.

Some part of bacterium Bacillus thuringiensis produce proteins that can kill certain type of insects.

During one of the growth phase of these Bacillus thuringiensis, they produce protein crystals which contain a toxic insecticidal protein. These proteins exist as inactive protoxins. When an insect swallow this inactive protoxins it gets activated. This happens because the gut of the insect has alkaline pH which solubilises the crystals. Once the protoxin is activated, it attaches itself to the surface of midgut epithelial cells and creates pores, which causes the cell to swell and in turn death of the insect.

In this way Bacillus thuringiensis has helped in developing pest resistance in crops.

Bt toxins are bio-pesticides, they are most widely used due to their efficiency and relatively cheap production.

Since most Bt toxins are insect-group specific, the choice of genes to be incorporated depends on the crop and the targeted pest.