Genetically modified crop, Bt cotton, Bt Tomato

Genetically modified plant

• In agriculture, Pest resistant plants are produced by biotechnology.  This kind of plant is called transgenic plants.

Read more about the Transgenic plants

• A bacteria Bacillus thuringiensis  produces a toxin because it has the Bt toxin gene.

• This gene has been isolated from bacteria and introduced in plants by using recombinant DNA technology and Bt corn, Bt rice, Bt potato, Bt tomato , By cotton have been produced.

• These plants are capable of providing resistance against the against without using any insecticides.

Bacillus thuringiensis (Bt)

• Strains of bacteria Bacillus thuringiensis produce a protein that kills insects of groups belonging to lepidoptera, coleoptera and diptera.

• Bacteria Bacillus thuringiensis form crystals of toxin protein during its life cycle. This toxin protein is present in the body of bacteria Bacillus thuringiensis in protoxin form. 

• As insects ingest plants, proteins are changed into active toxins due to the alkaline medium present in the gut of the insect.

• These toxin make target the epithelial cell of gut of insect and causing cell swelling and lysis and eventually causing death of insects .

• Most Bt toxin genes are insect specific therefore choice of gene depends on insect and plant.

• For Example - Protein encoded by gene cry I Ac and cry II Ab control the cotton bollworms and cry I Ab control corn borer.

• Bt crops are beneficial rather than using insecticides. But Main disadvantage of the Bt crop is the emergence of insect strains that may have resistance against the toxin.

Read more about the Transgenic animals

• Lectins, alpha amylase etc are other proteins with insecticidal properties that have also been explored. These proteins also retard the metabolism of insects and finally cause death of insects.

Ripening of Tomato

• Another valuable application of biotechnology is the delayed ripening of tomatoes.

• Plant hormone ethylene is involved in ripening of tomatoes. The formation of ethylene has been controlled by aminocyclopropane carboxylic acid.

• The genetic manipulation has been done by introducing an enzyme that breaks down the aminocyclopropane carboxylic acid.

• As a result, ethylene formation is restarted and there is a delay in ripening of tomatoes. This type of tomato is a transgenic tomato.