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Transgenic plants


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types of modifications alongwith advantages and disadvantages ethics included

Published in: Science
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Transgenic plants

  2. 2.  Was under trial and error for almost 9900 years.  The first genetically modified plant was produced in 1982, using an antibiotic-resistant tobacco plant.  The first genetically modified crop approved for sale in the U.S., in 1994, was the FlavrSavr tomato, which had a longer shelf life, as it took longer to soften after ripening.  As of mid-1996, a total of 35 approvals had been granted to commercially grow 8 transgenic crops and one flower crop of carnations, with 8 different traits in 6 countries plus the EU. In 2000, with the production of golden rice, scientists genetically modified food to increase its nutrient value for the first time. HISTORY
  3. 3. • 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 WHY GENETICALLY ENGINEER PLANTS?
  4. 4. Applications of Plant Genetic Engineering A.Crop Improvement B.Genetically Engineered Traits: The Big Six 1.Herbicide Resistance 2.Insect Resistance 3.Virus Resistance 4.Altered Oil Content 5.Delayed Fruit Ripening 6.Pollen Control C.Biotech Revolution: Cold and Drought Tolerance and Weather-Gaurd Genes D.Genetically Engineered Foods 1.Soybeans 2.Corn 3.Cotton 4.Other Crops
  5. 5. An Overview of the Crop Genetic Engineering cycle
  6. 6. Leaf Disc Method for A. t. Mediated Transformation Leaf Disk Preparation Co-cultivation with Agrobacterium Selection for Transformation Regeneration of Shoots 6
  7. 7. 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)dext ran- mediated Confined to protoplasts. Regeneration of fertile plants is frequently problematical Very less results
  8. 8.  Herbicides are generally non-selective (killing both weeds and crop plants) and must be applied before the crop plants germinate  Four potential ways to engineer herbicide resistant plants 1. Inhibit uptake of the herbicide 2. Overproduce the herbicide-sensitive target protein 3. Reduce the ability of the herbicide-sensitive target to bind to the herbicide 4. Give plants the ability to inactivate the herbicide HERBICIDES AND HERBICIDE-RESISTANT PLANTS
  9. 9. HERBICIDE-RESISTANT PLANTS: REDUCING THE ABILITY OF THE HERBICIDE-SENSITIVE TARGET TO BIND TO THE HERBICIDE  Herbicide: Glyphosate (better known as Roundup)  Resistance to Roundup (an inhibitor of the enzyme EPSP involved in aromatic amino acid biosynthesis) was obtained by finding a mutant version of EPSP from E. coli that does not bind Roundup and expressing it in plants (soybean, tobacco, petunia, tomato, potato, and cotton)  5-enolpyruvylshikimate-3-phosphate synthase (EPSP) is a chloroplast enzyme in the shikimate pathway and plays a key role in the synthesis of aromatic amino acids such as tyrosine and phenylalanine
  10. 10.  Genetic engineering here is more challenging; however, some strategies are possible:  Individually or in combination express pathogenesis- related (PR) proteins, which include b1,3-glucanases, chitinases, thaumatin-like proteins, and protease inhibitors  Overexpression of the NPR1 gene which encodes the “master” regulatory protein for turning on the PR protein genes  Overproducing salicylic acid in plants by the addition of two bacterial genes; SA activates the NPR1 gene and thus results in production of PR proteins FUNGUS- AND BACTERIUM-RESISTANT PLANTS
  11. 11. Modification of plant nutritional content: increasing the vitamin A content of plants • 124 million children worldwide are deficient in vitamin A, which leads to death and blindness • Mammals make vitamin A from b-carotene, a common carotenoid pigment normally found in plant photosynthetic membranes • Here, the idea was to engineer the b-carotene pathway into rice • The transgenic rice is yellow or golden in color and is called “golden rice” *Expression of enzymes of β-carotene pathway in rice endosperm *Amelioration of Vitamin A deficiency
  12. 12. Edible Vaccines – Ongoing Research Areas Hepatitis B Dental caries - Anti-tooth decay Ab Autoimmune diabetes Cholera Rabies HIV Rhinovirus Foot and Mouth Enteritis virus Malaria Influenza Cancer
  13. 13. EDIBLE VACCINES FROM PLANTS Two strategies for production 1) Expression of foreign antigens in plant via stable transformation 2) Delivery of vaccine epitopes via plant virus (Mason and Arntzen, 1995)
  14. 14. Strategy for the production of candidate vaccine antigens in plant tissues
  15. 15. e RABIES VIRUS G PROTEIN IN TOMATO • Gene linked to CaMV35S promoter • Introduced to tomato plants by Agrobacterium- mediated transformation • Expression of recombinant glycoprotein in leaves and fruits • Protein localized in Golgi bodies, vesicles and plasma lemma
  16. 16. Norwalk virus (cold virus) capsid protein in potato and tobacco • Causative agent for acute epidemic gastroenteritis • NVCP was fused to CaMV35S promoter • Transformation by Agrobacterium • Expression level: varies with plant (
  17. 17. DEVELOPMENT OF STRESS- AND SENESCENCE-TOLERANT PLANTS: GENETIC ENGINEERING OF SALT-RESISTANT PLANTS  Overexpression of the gene encoding a Na+/H+ antiport protein which transports Na+ into the plant cell vacuole  This has been done in Arabidopsis and tomato plants allowing them to survive on 200 mM salt (NaCl)
  18. 18. Frost Resistance • Ice-minus bacteria • Ice nucleation on plant surfaces caused by bacteria that aid in protein-water coalescence  forming ice crystals @ 0oC (320F) • Ice-minus Pseudomonas syringae • Modified by removing genes responsible for crystal formation • Sprayed onto plants • Displaces wild type strains • Protected to 23oF • Dew freezes beyond this point • Extends growth season • First deliberate release experiment – Steven Lindow – 1987- sprayed potatoes
  19. 19. Development of stress- and senescence-tolerant plants: genetic engineering of flavorful tomatoes Fruit ripening is a natural aging or senescence process that involves two independent pathways, flavor development and fruit softening. Typically, tomatoes are picked when they are not very ripe (i.e., hard and green) to allow for safe shipping of the fruit. Polygalacturonase is a plant enzyme that degrades pectins in plant cell walls and contribute to fruit softening. In order to allow tomatoes to ripen on the vine and still be hard enough for safe shipping of the fruit, polygalacturonase gene expression was inhibited by introduction of an antisense polygalacturonase gene and created the first commercial genetically engineered plant called the FLAVR SAVR tomato. Flavor development pathway Fruit softening pathway Green Red Hard Soft polygalacturonaseantisense polygalacturonase
  20. 20.  Crop Organization Gene  Brinjal IARI, New Delhi cr y1Ab, cr y1Ac  MAHYCO, Mumbai  Cauliflower MAHYCO, Mumbai cr y1Ac Sungrow Seeds Ltd., New Delhi  Cabbage Sungrow Seeds Ltd., New Delhi cr y1Ac  Chickpea ICRISAT, Hyderabad cr y1Ac, cr y1Ab  Groundnut ICRISAT, Hyderabad IPCVcp, IPCV replicase,  Maize Monsanto, Mumbia CP4 EPSPS  Mustard IARI, New Delhi CodA, Osmotin, NRCWS, Jabalpur bar, barnase, barstar TERI, New Delhi Ssu-maize, Psy, Ssu-tpCr tI UDSC, New Delhi bar, barnase, barstar  Okra MAHYCO, Mumbai cr y1Ac  Pigeonpea ICRISAT, Hyderabad cr y1Ab + SBTI MAHYCO, Mumbai cr y1Ac  Potato CPRI, Simla cr y1Ab NCPGR, New Delhi Ama-1  Rice Directorate of Rice Research, Bacterial blight res, Xa -21, Hyderabad Osmania University, Hyderabad cr y1Ab, gna gene, IARI, New Delhi gna MAHYCO, Mumbai Bt, chitinase, cr y1Ac and Aa MKU, Madurai cr y1Ac MSSRF, Chennai chitinase, B -1,3-glucanase TNAU, Coimbatore chitinase  Sorghum MAHYCO, Mumbai cr y1Ac Transgenic crop under development and field trials in India
  21. 21. • improved nutritional quality • increased crop yield • insect resistance • disease resistance • herbicide resistance • salt tolerance • biopharmaceuticals • saving valuable topsoil • ability to grow plants in harsh environments ADVANTAGES OF GM CROPS
  22. 22. • Damage to human health •allergies •horizontal transfer and antibiotic resistance •eating foreign DNA •changed nutrient levels • Damage to the natural environment •crop-to-weed gene flow •leakage of GM proteins into soil •reductions in pesticide spraying: are they real? • Disruption of current practices of farming and food production in developed countries •crop-to-crop gene flow • Disruption of traditional practices and economies in less developed countries. • Lack of research on consequences of transgenic crops. DISADVANTAGES OF GM CROPS
  23. 23.  Foods produced using biotechnology has not been established as safe and are not adequately regulated.  Crops produced using biotechnology will negatively impact the environment.  The long term effects of foods developed using biotechnology are unknown. MYTHS RELATED TO GENETIC MODIFICATION
  24. 24.  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. CONCLUSION
  25. 25.  Principles of genetic manipulations. PRIMROSE 5th EDITION  INTERNET  MOLECULAR BIOTECHNOLOGY by GLICK  REFERENCES