Applications of genetic engineering techniques in agriculture byB. DEVADATHA


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Applications of genetic engineering techniques in agriculture byB. DEVADATHA

  1. 1. Applications Of Genetic Engineering Techniques In Agriculture B.DEVADATHA 123680029 m.Sc biochemistry and
  2. 2. Why genetically engineer plants? • To improve the agricultural, horticultural or ornamental value of a crop plant • To serve as a bioreactor for the production of economically important proteins or metabolites • To provide a powerful means for studying the action of genes (and gene products) during development and other biological processes
  3. 3. Genetic engineering techniques applied to plants METHOD SALIENT FEATURES 1.VECTOR MEDIATED GENE TRANSFER a. Agrobacterium mediated gene transfer b. Plant viral vectors Very efficient but limited to a selected group of plants Ineffective, hence not widely used 2.DIRECT OR VECTORLESS DNA TRANSFER a. Electroporation b. Microprojectile c. Liposome fusion d. Silicon carbide fibres Mostly confined to protoplasts that can be regenerated to viable plants Limited use only one cell can be microinjected at a time Confined to protoplasts that can be regenerated into viable whole plants Requires regenerable cell suspensions 3 CHEMICAL METHODS a. Polyethylene glycol mediated b.Diethylaminoethyl(DEAE)dextra n- mediated Confined to protoplasts. Regeneration of fertile plants is frequently problematical Does not result in stable transformants
  4. 4. AGROBACTERIUM MEDIATED GENE TRANSFER • Agrobacterium tumefaciens is a naturally occurring Gram negative bacteria • Causes Crown gall disease by transferring T-DNA from its Ti plasmid in variety of dicotyledonous plants • Plants infected with this bacterium develop tumour like swellings galls that typically occur at crown of plant just above soil level • Following infection ,the bacterium transfers part of its DNA into plant & this DNA integrates into plant genome causing production of tumors and associated changes in plant metabolism
  5. 5. Process of Infection • A.tumefaciens infects plants through wounds • The motile bacterial cells are attracted to wound site by phenolic compounds such as acetosyringone secreted at wound site through specific chemotactic receptors present in bacterial membrane • Acetosyringone at higher concentrations activates Vir genes leading to production of proteins that are inserted into bacterial cell membrane for upake of opines produced by tumors • Acetosyringone also causes production of an Endonuclease that encodes a part of Ti plasmid termed T-DNA
  6. 6. Gene gun/Biolistic bombardment system  Desired DNA is coated on microscopic gold or tungsten beads  The particles are fired by a gun into plant tissue and penetrate the cell wall  DNA unwinds from gold carrier particle and enters the nucleus
  7. 7. Applications of Plant Genetic Engineering • Improved Nutritional Quality • Insect resistance • Disease resistance • Herbicide resistance • Salt tolerance • Delayed Fruit Ripening • Biopharmaceuticals and Vaccines
  8. 8. Improved Nutritional Quality • 124 million children worldwide are deficient in vitamin A, which leads to death and blindness • -carotene is precursor to vitamin A & consuming milled rice leads to vitamin A deficiency • Mammals make vitamin A from b-carotene, a common carotenoid pigment normally found in plant photosynthetic membranes Daffodil phytoene synthase gene carotene desaturase gene Daffodil lycopene -cyclase gene Endogenous human gene
  9. 9. RAINBOW CAULIFLOWER • Produced by traditional breeding –Non Transgenic • The Orange cauliflower has higher than normal levels of -carotene that encourages healthy skin • Purple colour comes from Anthocyanin which may prevent Heart disease by slowing blood clotting • Tests of the orange cauliflowers in America found that they contained 25 times the concentrations of beta carotene in normal cauliflowers
  10. 10. Insect resistance • It is estimated about 15% of world’s crop yield is lost through insects • Bacillus thuringiensis is a Gram negative ,soil bacterium produces parasporal crystalline proteinous toxin with insecticidal activity • When the Bt toxin gene was introduced into economically imp crop plants they develop resistanace for major insects obviating the need for use of insecticides • Bt toxin opens cation selective pores in membranes ,leadng to inflow of the cations into cells that causes osmotic lysis & destruction of epithelial cells • Bt genes could be expressed • in all parts of plants
  11. 11. Disease resistance plants • Genes that provide resistance against plant viruses have been successfully introduced into crop plants such as tobacco, tomato, rice, potato ,etc • Transgenic tobacco plant • Expressing tobacco mosaic virus coat protein gene were first developed • Viral capsids inhibit viral replication of TMV when infected • Virus coat protein mediated protection is successful for viruses with ss RNA
  12. 12. Herbicide resistance • Genes for resistance against certain Herbicides have been introduced into crop plants so they can thrive even when exposed to Herbicides • Glyphosate is a non selective Herbicide that inhibits 5- enolpyruvylshikimate-3-phosphate synthase (EPSP) a chloroplast enzyme in the shikimate pathway and plays a key role in the synthesis of aromatic amino acids such as tyrosine and phenylalanine • Herbicides Sulfonylureas & Imidazolines inhibits Acetolacetate (ALS),key enzyme in synthesis of Isoleucine ,Leucine & Valine • Some other Herbicide resistant plants also developed eg:bromoxynil,atrazine ,phenocarboxylic acids
  13. 13. Salt tolerance • A large fraction of world’s irrigated land cannot be used to grow most important crops due to increased salinity in soil • Resarcher’s have created transgenic tomatoes that grew well in saline soils • The transgene introduced was sodium/proton antiport pump that sequestered excess sodium in vacuole of leaf cells
  14. 14. Flavr savr tomato • Most tomatoes that have to be shipped to market are harvested before they are ripe otherwise, Ethylene synthesized by tomato causes them to ripen & spoil before they reach customer • Flavr savr tomatoes have been constructed that Express an antisense mRNA complementary to mRNA for an enzyme involved in ethylene Production These tomatoes make only 10% of normal amount of enzyme thus delaying ethylene production
  15. 15. Biopharmaceuticals and Vaccines • Expression of Hepatitis B Surface Antigen in Transgenic plants • Tobacco plants were genetically transformed with gene encoding Hepatitis B surface antigen (HBsAg) linked to a nominally constitutive promoter were generated • Recombinant HBsAg purified from transgenic plant had properties similar to Human serum derived HBsAg
  16. 16. Edible vaccines • Vaccines consisting of transgenic plant-derived antigens offer a new strategy for development of safe, inexpensive vaccines. • The vaccine antigens can be eaten with the edible part of the plant or purified from plant material Rabies- Tomato plants expressing rabies antigens could induce antibodies in mice Cholera-Transgenic potato with CT-B gene of Vibrio cholerae was shown to be efficacious in mice . Norwalk virus- transgenic potato expressing norwalk virus antigen showed seroconversion Hepatitis B- First human trials of a potato-based vaccine against hepatitis B have reported encouraging results If vaccines are intimately presented together with food, the guts immune system faces a conundrum
  17. 17. What are some of the advantages of GM foods? GM crops are more productive and have a larger yield. Offer more nutritional value and better flavor. A possibility that they could eliminate allergy-causing properties in some foods. Inbuilt resistance to pests, weeds and disease. More capable of thriving in regions with poor soil or adverse climates. More environment friendly as they require less herbicides and pesticides. Foods are more resistant and stay ripe for longer so they can be shipped long distances or kept on shop shelves for longer periods. As more GM crops can be grown on relatively small parcels of land, GM crops are an answer to feeding growing world populations.
  18. 18. What are some of the advantages of GM foods? • Disease resistance There are many viruses, fungi and bacteria that cause plant diseases. • Plant biologists are working to create plants with genetically-engineered resistance to these diseases. • Cold tolerance Unexpected frost can destroy sensitive seedlings. An antifreeze gene from cold water fish has been introduced into plants such as tobacco and potato. • With this antifreeze gene, these plants are able to tolerate cold temperatures that normally grow
  19. 19. Environmental & health impacts of GM crops • Toxic to harmless non-target species. Long-term exposure to pollen from GM insect resistant maize causes adverse effects on the behaviorand survival of the monarch butterfly • Toxic to beneficial insects. GM Bt crops adversely affectbeneficial insects important to controlling maize pests, such as green lacewings • A threat to soil ecosystems. Many Bt crops secrete their toxin from their roots into the soil. Residues left in the field contain the active Bt toxin • Risk for aquatic life. Leaves or grain from Bt maize can enter water courses where the toxin can accumulate in organismsand possibly exert a toxic effect
  20. 20. Environmental & health impacts of GM crops • Herbicide-tolerant crops may cross-pollinate weeds, resulting in "superweeds" • Certain gene products may be allergens, thus causing harm to human health • recent study found the Cry1Ab Bt toxin in the blood of pregnant women and their fetuses showing that it can cross the placental boundary • Studies indicate Roundup may be toxic to mammals and could interfere with hormones • There may be unintended harm to wildlife and beneficial insects
  21. 21. conclusion • Genetically-modified foods have the potential to solve many of the world's hunger and malnutrition problems, and to help protect and preserve the environment by increasing yield and reducing reliance upon chemical pesticides and herbicides. • Yet there are many challenges ahead for governments, especially in the areas of safety testing, regulation, international policy and food labeling. • Many people feel that genetic engineering is the inevitable wave of the future and that we cannot afford to ignore a technology that has such enormous potential benefits. • However, we must proceed with caution to avoid causing unintended harm to human health and the environment as a result of our enthusiasm for this powerful technology. • At the present time, genetically modified foods are dangerous for the world that we live in, not just for its people, but the delicate balance between organisms that inhabit it.
  22. 22. Sources • GM Science Review First Report (http:/ / www. bis. gov. uk/ files/ file15655. pdf), Prepared by the UK GM Science Review panel (July2003). • Maxmen, Amy (2 May 2012) First plant-made drug on the market (http:/ / blogs. nature. com/ news/ 2012/ 05/first-plant-made-drug-on-the- market. html) Nature, Biology & Biotechnology, Industry. Retrieved 26 June 2012 • Conner AJ, Glare TR, Nap JP. The release of genetically modified crops into the environment. Part II. Overview of ecological risk assessment (http:/ / www. ncbi. nlm. nih. gov/ pubmed/ 12943539) Plant J. 2003 Jan;33(1) • Vaccine antigen production in transgenic plants: strategies,gene constructs and perspectives • Principles of Gene Manipulation and Genomics Sandy B. Primrose, Richard Twyman