Bt Cotton / advantages/ disadvantages/gene construct/mechanism.pptx

This ppt describes in detail about the Bt cotton, how it was produced . it describes the mechanism by which the bt cotton / bt transgenics kill the pests , eg Helicoverpa armigera is the pest of cotton crop and is killed by the bt cotton advantages and disadvantages of Bt cottonare described with examples of few other proteins utilised in other crops to kill the pests .

1. Bt Cotton PLANT BIOTECHNOLOGY

2. Important Gene – Bt / Cry gene Gene taken from- Bacillus thuringiensis Gene added to- Cotton Gene codes for- Bt / cry protein(endotoxins) Helps cotton to be protected from – Heliothis armigera / Helicoverpa armigera ( bollworm)

3. Gene construct of Bt cotton

4. Cotton bollworm

5. Process (naturally) Delta endotoxin from bt bacteria. Proteases in insect body Insect die Disintegrate the lining of insect`s midgut Peptides (60-65 Kda ) Alkaline conditions

6. Introduction Endotoxin do not affect the mammals. Bt - Cotton : Reduce dependence on insecticides and pesticides soil bacterium Bacillus thuringiensis produces spore and during sporulation it produces crystalline inclusions ,delta toxins and protect themselves /itself from predator particularly soil borne insects.

7. when these spores are sprayed on the plants and insect larva takes it along leaves in the midgut of insects ,there are proteases which cleaves the large molecules of deltatoxin under alkaline pH resulting in 60-65 KDa peptide parts. These small peptides acts as toxin and larva dies. Thus, mode of action of Bt proteins requires binding to midgut epithelium receptor with appropriate pH situation in the pests and disruption of the midgut membranes.

8. The discovery of insecticidal proteins in soil bacteria Bacillus thuringiensis resulted in an enormous interest in the development of biopesticides. The endotoxin Bt binds to the cell membrane lining the gastrointestinal tract of the feeding insect causing disorganization of the membrane and killing of insect’s larvae. Bt toxin has been identified as relatively environmental friendly pesticide. It is biodegradable and do not accumulate in the tissue (there is no biomagnification) It is non toxic to vertebrates. Advantages

9. Scientists have being successful in isolating the genes that code for endotoxin the cry gene. The plants have been engineered to protect them from insects especially boll worm Heliothis armigera by incorporating cry gene in the plants. This can save billions of dollars that are spent every year for the control of cotton against boll worm. Cotton is among the most heavily pesticide treated crop involved thus transgenic cotton reduce our dependence on chemical pesticides with no danger to environment And also makes decreased input cost to farmers.

10. Disadvantages Bacterium Produces one microgram of toxin but every cell of cotton produces toxin and total is million tons in crop residues which becomes tons of Bt Toxin. It affects the microbial dynamics of soil which is not assessed. Insect may become resistant to bt toxins.

11. Conclusion Apart from Bt toxins several other proteins with insecticidal properties have been discovered example lactins , alpha amylase inhibitors, protease inhibitor. All of these proteins retard metabolism and growth of insects, when ingested in high dosage. The insects feeding on such transgenic plants cannot survive for long because of the damage of their digestive tract.

12. Thank You