Success Story of Transgenic crops Important Traits for Crop Improvement High crop yield High nutritional quality Abiotic stress tolerance Pest resistance Adaptation to.
Download ReportTranscript Success Story of Transgenic crops Important Traits for Crop Improvement High crop yield High nutritional quality Abiotic stress tolerance Pest resistance Adaptation to.
Success Story of Transgenic crops Important Traits for Crop Improvement High crop yield High nutritional quality Abiotic stress tolerance Pest resistance Adaptation to inter-cropping Nitrogen Fixation Insensitivity to photo-period Elimination of toxic compounds HYBRID DEVELOPMENT FOR HIGHER YIELD NUTRITIONAL QUALITY BIOTIC STRESS TOLERANCE TRANSGENIC PLANTS ENHANCED SHELF LIFE ABIOTIC STRESS TOLERANCE INDUSTRIAL PRODUCTS PHARMACEUTICALS & EDIBLE VACCINE 1985 1988 1992 1st transgenic plants produced Particle bombardment developed 1994 Flavr-Savr tomato is released 1996 Herbicide- and insect-resistant crops approved for cultivation GM crops considered substantially equivalent to hybrid varieties 4.3 million acres of GM crops planted 1998 GM food is dangerous (UK TV) Monarch butterfly paper causes uproar 1999 GM corn is excluded from its baby food Greenpeace starts anti-GM campaign 75 million acres of GM crops planted 2000 Golden rice with ß-carotene developed McDonald’s rejects GM potatoes Tearless Onion Colorful Cauliflowers Purple tomatoes Blue Roses The big five successful traits Insect Resistance Delayed Fruit Ripening Nutritional Enhancing Herbicide Resistance Virus Resistance Herbicide Resistance Glyphosate Resistance i. Glyphosate = “Roundup”, “Tumbleweed” = Systemic herbicide ii. Marketed under the name Roundup, glyphosate inhibits the enzyme EPSPS (S-enolpyruvlshikimate-3 phosphate – involved in chloroplast amino acid synthesis), makes aromatic amino acids. iii. The gene encoding EPSPS has been transferred from glyphosateresistant E. coli into plants, allowing plants to be resistant. Glufosinate Resistance i. Glufosinate (the active ingredient being phosphinothricin) mimics the structure of the amino acid glutamine, which blocks the enzyme glutamate synthase. ii. Plants receive a gene from the bacterium Streptomyces (bar gene) that produce a protein that inactivates the herbicide. Herbicide Resistance Bromoxynil Resistance i. A gene encoding the enzyme bromoxynil nitrilase (BXN) is transferred from Klebsiella pneumoniae bacteria to plants. ii. Nitrilase inactivates the Bromoxynil before it kills the plant. Sulfonylurea. i. Kills plants by blocking an enzyme needed for synthesis of the amino acids valine, leucine, and isoleucine. ii. Resistance generated by mutating a gene in tobacco plants (acetolactate synthase), and transferring the mutated gene into crop plants. Roundup Ready™ Soybeans A problem in agriculture is the reduced growth of crops imposed by the presence of unwanted weeds. Herbicides such as RoundupTM and Liberty LinkTM are able to kill a wide range of weeds and have the advantage of breaking down easily. Development of herbicide resistant crops allows the elimination of surrounding weeds without harm to the crops. ROUNDUP (Glyphosate) RESISTANCE ( HERBICIDE TOLERANCE IN CROPS) Glucose ROUNDUP (Glyphosate ) 3 phosphoglycerate Tryptophan Glycolysis EPSP SYNTHASE Phosphoenol pyruvate EPSP SYNTHASE Tyrosine Phenylalaline ROUNDUP (Glyphosate ) In transgenic plant, herbicide cannot bind the mutant of EPSPS (Roundup resistant cotton and soybean) Insect resistance Anti-Insect Strategy - Insecticides a) Toxic crystal protein from Bacillus thuringensis Toxic crystals found during sporulation Alkaline protein degrades gut wall of lepidopteran larvae • Corn borer catepillars • Cotton bollworm catepillars • Tobacco hornworm catepillars • Gypsy moth larvae Sprayed onto plants – but will wash off The Bt toxin isolated from Bacillus thuringiensis has been used in plants. The gene has been placed in corn, cotton, and potato, and has been marketed. Insect Resistance Various insect resistant crops have been produced. Most of these make use of the Cry gene in the bacteria Bacillus thuringiensis (Bt); this gene directs the production of a protein that causes paralysis and death to many insects. Corn hybrid with a Bt gene Corn hybrid susceptible to European corn borer δ -endotoxin gene (Cry gene) of Bacillus thuriengenesis GENE FOR Bt TOXIN WAS TRANSFERRED TO OBTAIN BT TRANSGENIC PLANTS PLANT SYNTHESIZES INACTIVE PROTOXIN INSECT FEEDS ON TRANSGENIC PLANT PROTEINASE DIGESTION IN INSECT GUT MAKES THE ACTIVE TOXIN Toxin binds a receptor on the gut epithelial cells, forms a channel on the membrane. This causes electrolyte leakage and insect death Virus resistance a) Plants may be engineered with genes for resistance to viruses, bacteria, and fungi. b) Virus-resistant plants have a viral protein coat gene that is overproduced, preventing the virus from reproducing in the host cell, because the plant shuts off the virus’ protein coat gene in response to the overproduction. c) Coat protein genes are involved in resistance to diseases such as cucumber mosaic virus, tobacco rattle virus, and potato virus X. Delayed Fruit Ripening a) Allow for crops, such as tomatoes, to have a higher shelf life. b) Tomatoes generally ripen and become soft during shipment to a store. c) Tomatoes are usually picked and sprayed with the plant hormone ethylene to induce ripening, although this does not improve taste d) Tomatoes have been engineered to produce less ethylene so they can develop more taste before ripening, and shipment to markets Delayed Fruit Ripening What happened to the Flavr Savr tomato? i. Produced by blocking the polygalacturonase (PG) gene, which is involved in spoilage. PG is an enzyme that breaks down pectin, which is found in plant cell walls. ii. Plants were transformed with the anti-sense PG gene, which is mRNA that base pair with mRNA that the plant produces, essentially blocking the gene from translation. iii.First genetically modified organism to be approved by the FDA, in 1994. iv.Tomatoes were delicate, did not grow well in Florida, and cost much more than regular tomatoes. v. Calgene was sold to Monsanto after Monsanto filed a patentinfringement lawsuit against Calgene, and the Flavr Savr tomato left the market. First biotech plant product – Flav’r Sav’r tomato “Rot-Resistant Tomato” Anti-sense gene complementary to polygalacturonase (PG) PG = pectinase accelerates plant decay/rotting Nutritionally Enhanced Plants 1.More than one third of the world’s population relies on rice as a food staple, so rice is an attractive target for enhancement. 2.Golden Rice was genetically engineered to produce high levels of beta-carotene, which is a precursor to vitamin A. Vitamin A is needed for proper eyesight. 3.Other enhanced crops include iron-enriched rice and tomatoes with three times the normal amount of betacarotene Golden Rice Normal rice Transgenic technology produced a type of rice that accumulates beta-carotene in rice grains. Once inside the body, beta-carotene is converted to vitamin A. “Normal” rice “Golden” rice Gernayl Gernayl diphosphate (GGPP) Phytoene synthase Phytoene Phytoene desaturase Lycopene Lycopene cyclase Beta carotene Complete biochemical pathway in the rice for production of beta-carotene, a precursor for vitamin A The prototype of golden rice was developed in 2000 and is a light yellow color (b). It contains 1.6 mg/g of carotenoid. In 2005, new transgenic lines were developed that dramatically increased the amount of carotenoid synthesized, making the rice a deep golden color (c). This latest form contains 37 mg/g of carotenoid, of which 84% is b-carotene – trial Molecular Farming 1.A new field where plants and animals are genetically engineered to produce important pharmaceuticals, vaccines, and other valuable compounds. 2.Plants may possibly be used as bioreactors to mass-produce chemicals that can accumulate within the cells until they are harvested. 3.Soybeans have been used to produce monoclonal antibodies with therapeutic value for the treatment of colon cancer. Drugs can also be produced in rice, corn, and tobacco plants 4.Plants have been engineered to produce human antibodies against HIV. Pharmaceuticals has begun clinical trials with herpes antibodies produced in plants. Why Plants? Plants offer unique benefits for the production of pharmaceutical proteins: Ease of Scale-up Low Cost Reduced Capital Expenditures No Animal Contaminants (virus) Molecular Farming (Vaccines) a) Making plants that produce vaccines b) Potatoes have been studied using a portion of the E. coli enterotoxin in mice and humans. c) Other candidates for edible vaccines include banana and tomato, and alfalfa, corn, and wheat are possible candidates for use in livestock. d) Edible vaccines may lead to the eradication of diseases such as hepatitis B and polio. Pharmaceutical Production in Plants Genetically modified plants have been used as “bioreactors” to produce therapeutic proteins for more than a decade. A recent contribution by transgenic plants is the generation of edible vaccines. Edible vaccines are vaccines produced in plants that can be administered directly through the ingestion of plant materials containing the vaccine. Eating the plant would then confer immunity against diseases. Edible vaccines produced by transgenic plants are attractive for many reasons. The cost associated with the production of the vaccine is low, especially since the vaccine can be ingested directly, and vaccine production can be rapidly up scaled should the need arises. Edible vaccine is likely to reach more individuals in developing countries. The first human clinical trial took place in 1997. Vaccine against the toxin from the bacteria E.coli was produced in potato. Ingestion of this transgenic potato resulted in satisfactory vaccinations and no adverse effects. Edible Vaccines One focus of current vaccine effort is on hepatitis B, a virus responsible for causing chromic liver disease. Transgenic tobacco and potatoes were engineered to express hepatitis B virus vaccine. During the past two years, vaccines against a E.coli toxin, the respiratory syncytial virus, measles virus, and the Norwalk virus have been successfully expressed in plants and delivered orally. These studies have supported the potential of edible vaccines as preventive agents of many diseases. There is hope to produce edible vaccines in bananas, which are grown extensively throughout the developing world. Molecular Farming (Biopolymers and Plants) a) Plant seeds may be a potential source for plastics that could be produced and easily extracted. b) A type of PHA (polyhydroxylalkanoate) polymer called “poly-beta-hydroxybutyrate”, or PHB, is produced in Arabidopsis, or mustard plant. c) PHB can be made in canola seeds by the transfer of three genes from the bacterium Alicaligenes eutrophus, which codes for enzymes in the PHB synthesis pathway. d) A polymer called PHBV produced through Alicaligenes fermentation, which is sold under the name Biopol.